Journal of Materials Science and Engineering B, 2014
Rare earth double doped lead titanate with general formula Pb 1-x Pr x Ti 1-y Y y O 3 where x (pr... more Rare earth double doped lead titanate with general formula Pb 1-x Pr x Ti 1-y Y y O 3 where x (praseodymium) = 0.02, 0.04, 0.06, 0.08 and y (yttrium) = 0.02 was synthesized by solid state reaction technique. X-ray diffraction analysis confirms single phase formation with perovskite structure having tetragonal phase. Micro-structural analysis shows formation of dense micro-structure with grain size calculated using average line intercepted method. Dielectric behavior as a function of temperature was found to decrease with Pr substitution. The diffusivity in the dielectric behavior was observed in all the compositions. Piezoelectric coefficient d 33 and g 33 was determined with increase in compositions of Pr substituent. The ferroelectric property was observed at room temperature and the value of remanent polarization (P r), spontaneous polarization (P s) and (E C) coercive field was calculated.
Lead niobate zirconate titanate (PNZT) with general formula 0.5PbNb 2 O 6-0.5Pb(Zr x Ti 1-x)O 3 (... more Lead niobate zirconate titanate (PNZT) with general formula 0.5PbNb 2 O 6-0.5Pb(Zr x Ti 1-x)O 3 (where x = 0.15, 0.25, 0.35) and lead nickel niobate zirconate titanate (PNNZT) with general formula Pb(Ni x Nb 0.5-x Zr 0.25 Ti 0.25)O 3 (where x = 0.167, 0.250, 0.333) have been prepared by conventional solid state reaction. The phase formation has been studied by Xray diffraction analysis. Raman investigations have been carried out in the 200-1000 cm −1 wave number range. The structural changes observed in the Xray diffraction pattern has been further confirmed by Raman analysis. The major changes in the E(1TO), A 1 (1TO) and E + B 1 phonon modes suggest the structural change from cubic to rhombohedral with increase in Ni concentration in PNNZT. The optical band gap has been calculated from UV-Vis absorption spectra.
Journal of Materials Science: Materials in Electronics, 2016
the similar trend, suggesting the temperature dependent dielectric relaxation. The Cr doping enha... more the similar trend, suggesting the temperature dependent dielectric relaxation. The Cr doping enhances the dielectric properties of GdMnO 3. The room temperature magnetic behaviour analyzed from the magnetic ield dependent magnetization curves suggests paramagnetic behavior for both the composition; however Cr doping does enhance the magnetization.
Cerium orthovanadate, neodymium orthovanadate and mixed cerium neodymium orthovanadate nanopartic... more Cerium orthovanadate, neodymium orthovanadate and mixed cerium neodymium orthovanadate nanoparticles was prepared by co-precipitation method. Powder X-ray diffraction reveals tetragonal zircon structure. Slight increase in lattice parameter, volume and decrease in X-ray density inferred that Ce 3+ and Nd 3+ ion replaces each other. Transmission electron microscopy suggests change in morphology with the effect of mixing and validates formation of nanocrystalline material. The infrared transmittance spectrum confirmed the presence of various functional groups. Dielectric properties as function of frequency show dielectric constant and loss tangent decreases with increase in frequency which is due to Maxwell-Wagner type interfacial polarization. The variation of AC conductivity measurement with frequency suggests conduction mechanism due to large polaron hopping in CeV whereas small polaron in mixed CeNdV. The activation energy decreases with rising frequency indicates the conduction mechanism is based on polaron hopping between localized states in disordered manner.
A ternary system of lead niobate–lead zirconate–lead titanate with composition xPN–yPZ–(x-y)PT wh... more A ternary system of lead niobate–lead zirconate–lead titanate with composition xPN–yPZ–(x-y)PT where x=0.5 and y=0.15, 0.25, and 0.35 known as PNZT has been prepared by conventional mixed oxide route at a temperature of 1100°C. The formation of the perovskite phase was established by X-ray diffraction analysis. The surface morphology studied by scanning electron microscopy shows the formation of fairly dense grains and elemental composition was confirmed by energy dispersive X-ray analysis. Dielectric properties like dielectric constant and dielectric loss (ε′ and tanδ) indicate poly-dispersive nature of the material. The temperature dependent dielectric constant (ε′) curve indicates relaxor behaviour with two dielectric anomalies. The poly-dispersive nature of the material was analysed by Cole-Cole plots. The activation energy follows the Arrhenius law and is found to decrease with increasing frequency for each composition. The frequency dependence of ac conductivity follows the u...
Magnesium hydrogen phosphate (MHP) and transition metal doped cadmium magnesium hydrogen phosphat... more Magnesium hydrogen phosphate (MHP) and transition metal doped cadmium magnesium hydrogen phosphate (CdMHP) was synthesized in the form of crystalline material by room temperature solution technique known as gel encapsulation technique. The synthesized crystals were then characterized for their structural, mechanical and electrical investigations using various chemical and physical methods. X-ray diffraction analysis (XRD) establishes magnesium hydrogen phosphate and cadmium magnesium hydrogen phosphate belonging to orthorhombic crystal system with space group Pbca. The mechanical behaviour of these crystals was studied by calculating Vicker's hardness number. The behaviour of microhardness with applied load was observed to be complex. The electrical behaviour was carried out by calculating dielectric constant at different temperatures and for different frequencies. The dielectric constant (ε /) was found to be strongly dependent on temperature and frequency. The transition metal doping of cadmium in magnesium hydrogen phosphate remarkably decrease the value of dielectric constant from 68 to 23. The transition temperature also decreases from 330˚C in case of magnesium hydrogen phosphate to 310˚C in case of cadmium magnesium hydrogen phosphate.
Abstract Lead nickel niobate–lead zirconate titanate (PNNZT) and cadmium doped (CdPNNZT) with gen... more Abstract Lead nickel niobate–lead zirconate titanate (PNNZT) and cadmium doped (CdPNNZT) with general composition Pb 1.0 (Ni 0.167 Nb 0.333 Zr 0.155 Ti 0.345 )O 3 (PNNZT), Pb 0.98 Cd 0.02 (Ni 0.167 Nb 0.333 Zr 0.155 Ti 0.345 )O 3 (CdPNNZT) respectively were prepared by conventional solid state reaction. Microstructural and compositional analyses have been carried out by X-ray diffraction and scanning electron microscopy. With cadmium doping there is an increase in both the perovskite phase and in grain size. The effect of cadmium doping on the structural and dielectric properties has been investigated. An increase in the dielectric constant was observed with cadmium doping in PNNZT. Complex impedance analysis suggests poly-dispersive non-Debye type relaxation to occur in the material. The frequency dependence of AC conductivity obeys the universal double power law. The value of activation energy depends on increase in frequency as well as on cadmium doping.
Samarium doped calcium hydrogen phosphate was synthesized as single crystal by room temperature s... more Samarium doped calcium hydrogen phosphate was synthesized as single crystal by room temperature solution growth technique, namely, silica gel technique. The kinetics of the growth parameters was studied with regard to variation of pH, dopant concentration, gel ageing, and upper reactant concentration. The optimum conditions for the growth of good quality single crystal were worked out. Single crystal X-ray diffraction analysis establishes that the crystal belongs to monoclinic system. The density observed by the flotation method is greater than the density of the reported pure calcium hydrogen phosphate thereby suggesting the incorporation of the dopant (Sm) ion into the lattice of host (CHP). Thermal analysis gave two sharp endothermic peaks which are due to partial dehydration and phase transition, respectively. Dielectric studies establish a shift in the Curie temperature from 355 to 370°C only at higher frequencies thereby suggesting the relaxational behavior of the material.
The solid solutions of lead nickel niobate (PNN) and lead zirconate titanate (PZT), with general ... more The solid solutions of lead nickel niobate (PNN) and lead zirconate titanate (PZT), with general formula 0.5 Pb(NixNb1-x)O3-0.5 PZT, where x = 1/3, 1/2 and 2/3 and Zr/Ti = 50/50, were prepared by conventional solid state reaction technique. The perovskite phase formation and morphology were examined by powder X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques. From microstructure investigations, the grain size was found to lie in the range of 0.2-1.1 ?m. Diffuse phase transition and dielectric relaxation was obtained for all three compositions. The nature of dielectric relaxation was investigated through complex plane Argand plot or Cole-Cole plot. It was found that both grains as well as grain boundary contribute to dielectric relaxation. A direct correlation between the grain size and electrical properties was obtained. The remnant polarization and grain size were found to follow the inverse relationship. The inverse relationship between remnant polarization...
The Type Three Secretion System (T3SS), or injectisome, is a macromolecular infection machinery p... more The Type Three Secretion System (T3SS), or injectisome, is a macromolecular infection machinery present in many pathogenic Gram-negative bacteria. It consists of a basal body, anchored in both bacterial membranes, and a hollow needle through which effector proteins are delivered into the target host cell. Two different architectures of the T3SS needle have been previously proposed. First, an atomic model of the Salmonella typhimurium needle was generated from solid-state NMR data. The needle subunit protein, PrgI, comprises a rigid-extended N-terminal segment and a helix-loop-helix motif with the N-terminus located on the outside face of the needle. Second, a model of the Shigella flexneri needle was generated from a high-resolution 7.7-Å cryo-electron microscopy density map. The subunit protein, MxiH, contains an Nterminal a-helix, a loop, another a-helix, a 14-residue-long b-hairpin (Q51-Q64) and a C-terminal a-helix, with the Nterminus facing inward to the lumen of the needle. In the current study, we carried out solid-state NMR measurements of wild-type Shigella flexneri needles polymerized in vitro and identified the following secondary structure elements for MxiH: a rigid-extended N-terminal segment (S2-T11), an a-helix (L12-A38), a loop (E39-P44) and a C-terminal a-helix (Q45-R83). Using immunogold labeling in vitro and in vivo on functional needles, we located the N-terminus of MxiH subunits on the exterior of the assembly, consistent with evolutionary sequence conservation patterns and mutagenesis data. We generated a homology model of Shigella flexneri needles compatible with both experimental data: the MxiH solid-state NMR chemical shifts and the state-of-the-art cryoEM density map. These results corroborate the solid-state NMR structure previously solved for Salmonella typhimurium PrgI needles and establish that Shigella flexneri and Salmonella typhimurium subunit proteins adopt a conserved structure and orientation in their assembled state. Our study reveals a common structural architecture of T3SS needles, essential to understand T3SS-mediated infection and develop treatments.
The Type Three Secretion System (T3SS), or injectisome, is a macromolecular infection machinery p... more The Type Three Secretion System (T3SS), or injectisome, is a macromolecular infection machinery present in many pathogenic Gram-negative bacteria. It consists of a basal body, anchored in both bacterial membranes, and a hollow needle through which effector proteins are delivered into the target host cell. Two different architectures of the T3SS needle have been previously proposed. First, an atomic model of the Salmonella typhimurium needle was generated from solid-state NMR data. The needle subunit protein, PrgI, comprises a rigid-extended N-terminal segment and a helix-loop-helix motif with the N-terminus located on the outside face of the needle. Second, a model of the Shigella flexneri needle was generated from a high-resolution 7.7-Å cryo-electron microscopy density map. The subunit protein, MxiH, contains an Nterminal a-helix, a loop, another a-helix, a 14-residue-long b-hairpin (Q51-Q64) and a C-terminal a-helix, with the Nterminus facing inward to the lumen of the needle. In the current study, we carried out solid-state NMR measurements of wild-type Shigella flexneri needles polymerized in vitro and identified the following secondary structure elements for MxiH: a rigid-extended N-terminal segment (S2-T11), an a-helix (L12-A38), a loop (E39-P44) and a C-terminal a-helix (Q45-R83). Using immunogold labeling in vitro and in vivo on functional needles, we located the N-terminus of MxiH subunits on the exterior of the assembly, consistent with evolutionary sequence conservation patterns and mutagenesis data. We generated a homology model of Shigella flexneri needles compatible with both experimental data: the MxiH solid-state NMR chemical shifts and the state-of-the-art cryoEM density map. These results corroborate the solid-state NMR structure previously solved for Salmonella typhimurium PrgI needles and establish that Shigella flexneri and Salmonella typhimurium subunit proteins adopt a conserved structure and orientation in their assembled state. Our study reveals a common structural architecture of T3SS needles, essential to understand T3SS-mediated infection and develop treatments.
Lead niobate zirconate titanate (PNZT) with general formula 0.5PbNb2O6–0.5Pb(ZrxTi1-x)O3 (where x... more Lead niobate zirconate titanate (PNZT) with general formula 0.5PbNb2O6–0.5Pb(ZrxTi1-x)O3 (where x = 0.15, 0.25, 0.35) and lead nickel niobate zirconate titanate (PNNZT) with general formula Pb(NixNb0.5-xZr0.25Ti0.25)O3 (where x = 0.167, 0.250, 0.333) have been prepared by conventional solid state reaction. The phase formation has been studied by X – ray diffraction analysis. Raman investigations have been carried out in the 200–1000 cm−1 wave number range. The structural changes observed in the X – ray diffraction pattern has been further confirmed by Raman analysis. The major changes in the E(1TO), A1(1TO) and E+B1 phonon modes suggest the structural change from cubic to rhombohedral with increase in Ni concentration in PNNZT. The optical band gap has been calculated from UV – Vis absorption spectra. Keywords PNZT . X-ray diffraction . Raman spectra . Absorption spectra . Band gap
Rare earth double doped lead titanate with general formula Pb 1-x Pr x Ti 1-y Y y O 3 where x (pr... more Rare earth double doped lead titanate with general formula Pb 1-x Pr x Ti 1-y Y y O 3 where x (praseodymium) = 0.02, 0.04, 0.06, 0.08 and y (yttrium) = 0.02 was synthesized by solid state reaction technique. X-ray diffraction analysis confirms single phase formation with perovskite structure having tetragonal phase. Micro-structural analysis shows formation of dense micro-structure with grain size calculated using average line intercepted method. Dielectric behavior as a function of temperature was found to decrease with Pr substitution. The diffusivity in the dielectric behavior was observed in all the compositions. Piezoelectric coefficient d 33 and g 33 was determined with increase in compositions of Pr substituent. The ferroelectric property was observed at room temperature and the value of remanent polarization (P r), spontaneous polarization (P s) and (E C) coercive field was calculated.
Pure and cerium mixed neodymium orthophosphate was synthesized as nanoparticles via wet chemical ... more Pure and cerium mixed neodymium orthophosphate was synthesized as nanoparticles via wet chemical co-precipitation technique. Powder X-ray diffraction (PXRD) study suggests that the average crystallite size and X-ray density decreases with the mixing of cerium in neodymium orthophosphate. Scanning electron microscope (SEM) and transmission electron microscope (TEM) studies revealed spherical morphology for neodymium orthophosphate but when cerium is mixed the morphology changes into rectangular platelet, like nanorods. Fourier transform infrared (FTIR) spectroscopy signifies slightly shifting of bands towards lower wave number and the force constant were also calculated. Thermal analysis suggests that the material get stabilized after 425 C and structural phase transition was seen above 800 C. Optical absorption spectrum give various absorption bands corresponding to each wavelength revealing transitions of Nd 3þ and Ce 3þ present in the UV-VIS region and optical band gap energy decreases from 3.3 to 2.4 eV. Mixing of cerium in neodymium orthophosphate enhances the value of dielectric constant and decreases the transition temperature. The value of exponent 'n' suggest that in neodymium orthophosphate, conduction is through hopping mechanism but for cerium neodymium orthophosphate conduction correspond to long range diffusion of ions.
A B S T R A C T Cerium orthovanadate, neodymium orthovanadate and mixed cerium neodymium orthovan... more A B S T R A C T Cerium orthovanadate, neodymium orthovanadate and mixed cerium neodymium orthovanadate nanoparticles was prepared by co-precipitation method. Powder X-ray diffraction reveals tetragonal zircon structure. Slight increase in lattice parameter, volume and decrease in X-ray density inferred that Ce 3+ and Nd 3+ ion replaces each other. Transmission electron microscopy suggests change in morphology with the effect of mixing and validates formation of nanocrystalline material. The infrared transmittance spectrum confirmed the presence of various functional groups. Dielectric properties as function of frequency show dielectric constant and loss tangent decreases with increase in frequency which is due to Maxwell–Wagner type interfacial polarization. The variation of AC conductivity measurement with frequency suggests conduction mechanism due to large polaron hopping in CeV whereas small polaron in mixed CeNdV. The activation energy decreases with rising frequency indicates the conduction mechanism is based on polaron hopping between localized states in disordered manner.
A ternary system of lead niobate–lead zirconate–lead titanate with composition xPN–yPZ–(x-y)PT wh... more A ternary system of lead niobate–lead zirconate–lead titanate with composition xPN–yPZ–(x-y)PT where í µí±¥ = 0.5 and í µí±¦ = 0.15, 0.25, and 0.35 known as PNZT has been prepared by conventional mixed oxide route at a temperature of 1100 ∘ C. The formation of the perovskite phase was established by X-ray diffraction analysis. The surface morphology studied by scanning electron microscopy shows the formation of fairly dense grains and elemental composition was confirmed by energy dispersive X-ray analysis. Dielectric properties like dielectric constant and dielectric loss (í µí¼ í® í° and tan í µí»¿) indicate poly-dispersive nature of the material. The temperature dependent dielectric constant (í µí¼ í® í°) curve indicates relaxor behaviour with two dielectric anomalies. The poly-dispersive nature of the material was analysed by Cole-Cole plots. The activation energy follows the Arrhenius law and is found to decrease with increasing frequency for each composition. The frequency dependence of ac conductivity follows the universal power law. The ac conductivity analysis suggests that hopping of charge carriers among the localized sites is responsible for electrical conduction. The ferroelectric studies reveal that these ternary systems are soft ferroelectric.
the similar trend, suggesting the temperature dependent dielectric relaxation. The Cr doping enha... more the similar trend, suggesting the temperature dependent dielectric relaxation. The Cr doping enhances the dielectric properties of GdMnO 3 . The room temperature magnetic behaviour analyzed from the magnetic field dependent magnetization curves suggests paramagnetic behavior for both the composition; however Cr doping does enhance the magnetization.
The solid solutions of lead nickel niobate (PNN) and lead zirconate titanate (PZT), with general ... more The solid solutions of lead nickel niobate (PNN) and lead zirconate titanate (PZT), with general formula 0.5 Pb(NixNb1-x)O3-0.5 PZT, where x = 1/3, 1/2 and 2/3 and Zr/Ti = 50/50, were prepared by conventional solid state reaction technique. The perovskite phase formation and morphology were examined by powder X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques. From microstructure investigations, the grain size was found to lie in the range of 0.2–1.1 μm. Diffuse phase transition and dielectric relaxation was obtained for all three compositions. The nature of dielectric relaxation was investigated through complex plane Argand plot or Cole-Cole plot. It was found that both grains as well as grain boundary contribute to dielectric relaxation. A direct correlation between the grain size and electrical properties was obtained. The remnant polarization and grain size were found to follow the inverse relationship. The inverse relationship between remnant polarization and grain size was established.
Samarium doped calcium hydrogen phosphate was synthesized as single crystal by room temperature s... more Samarium doped calcium hydrogen phosphate was synthesized as single crystal by room temperature solution growth technique, namely, silica gel technique.The kinetics of the growth parameters was studiedwith regard to variation of pH, dopant concentration, gel ageing, and upper reactant concentration. The optimum conditions for the growth of good quality single crystal were worked out. Single crystal X-ray diffraction analysis establishes that the crystal belongs to monoclinic system.The density observed by the flotation method is greater than the density of the reported pure calciumhydrogen phosphate thereby suggesting the incorporation of the dopant (Sm) ion into the lattice of host (CHP). Thermal analysis gave two sharp endothermic peaks which are due to partial dehydration and phase transition, respectively. Dielectric studies establish a shift in the Curie temperature from 355 to 370∘C only at higher frequencies thereby suggesting the relaxational behavior of the material.
Journal of Materials Science and Engineering B, 2014
Rare earth double doped lead titanate with general formula Pb 1-x Pr x Ti 1-y Y y O 3 where x (pr... more Rare earth double doped lead titanate with general formula Pb 1-x Pr x Ti 1-y Y y O 3 where x (praseodymium) = 0.02, 0.04, 0.06, 0.08 and y (yttrium) = 0.02 was synthesized by solid state reaction technique. X-ray diffraction analysis confirms single phase formation with perovskite structure having tetragonal phase. Micro-structural analysis shows formation of dense micro-structure with grain size calculated using average line intercepted method. Dielectric behavior as a function of temperature was found to decrease with Pr substitution. The diffusivity in the dielectric behavior was observed in all the compositions. Piezoelectric coefficient d 33 and g 33 was determined with increase in compositions of Pr substituent. The ferroelectric property was observed at room temperature and the value of remanent polarization (P r), spontaneous polarization (P s) and (E C) coercive field was calculated.
Lead niobate zirconate titanate (PNZT) with general formula 0.5PbNb 2 O 6-0.5Pb(Zr x Ti 1-x)O 3 (... more Lead niobate zirconate titanate (PNZT) with general formula 0.5PbNb 2 O 6-0.5Pb(Zr x Ti 1-x)O 3 (where x = 0.15, 0.25, 0.35) and lead nickel niobate zirconate titanate (PNNZT) with general formula Pb(Ni x Nb 0.5-x Zr 0.25 Ti 0.25)O 3 (where x = 0.167, 0.250, 0.333) have been prepared by conventional solid state reaction. The phase formation has been studied by Xray diffraction analysis. Raman investigations have been carried out in the 200-1000 cm −1 wave number range. The structural changes observed in the Xray diffraction pattern has been further confirmed by Raman analysis. The major changes in the E(1TO), A 1 (1TO) and E + B 1 phonon modes suggest the structural change from cubic to rhombohedral with increase in Ni concentration in PNNZT. The optical band gap has been calculated from UV-Vis absorption spectra.
Journal of Materials Science: Materials in Electronics, 2016
the similar trend, suggesting the temperature dependent dielectric relaxation. The Cr doping enha... more the similar trend, suggesting the temperature dependent dielectric relaxation. The Cr doping enhances the dielectric properties of GdMnO 3. The room temperature magnetic behaviour analyzed from the magnetic ield dependent magnetization curves suggests paramagnetic behavior for both the composition; however Cr doping does enhance the magnetization.
Cerium orthovanadate, neodymium orthovanadate and mixed cerium neodymium orthovanadate nanopartic... more Cerium orthovanadate, neodymium orthovanadate and mixed cerium neodymium orthovanadate nanoparticles was prepared by co-precipitation method. Powder X-ray diffraction reveals tetragonal zircon structure. Slight increase in lattice parameter, volume and decrease in X-ray density inferred that Ce 3+ and Nd 3+ ion replaces each other. Transmission electron microscopy suggests change in morphology with the effect of mixing and validates formation of nanocrystalline material. The infrared transmittance spectrum confirmed the presence of various functional groups. Dielectric properties as function of frequency show dielectric constant and loss tangent decreases with increase in frequency which is due to Maxwell-Wagner type interfacial polarization. The variation of AC conductivity measurement with frequency suggests conduction mechanism due to large polaron hopping in CeV whereas small polaron in mixed CeNdV. The activation energy decreases with rising frequency indicates the conduction mechanism is based on polaron hopping between localized states in disordered manner.
A ternary system of lead niobate–lead zirconate–lead titanate with composition xPN–yPZ–(x-y)PT wh... more A ternary system of lead niobate–lead zirconate–lead titanate with composition xPN–yPZ–(x-y)PT where x=0.5 and y=0.15, 0.25, and 0.35 known as PNZT has been prepared by conventional mixed oxide route at a temperature of 1100°C. The formation of the perovskite phase was established by X-ray diffraction analysis. The surface morphology studied by scanning electron microscopy shows the formation of fairly dense grains and elemental composition was confirmed by energy dispersive X-ray analysis. Dielectric properties like dielectric constant and dielectric loss (ε′ and tanδ) indicate poly-dispersive nature of the material. The temperature dependent dielectric constant (ε′) curve indicates relaxor behaviour with two dielectric anomalies. The poly-dispersive nature of the material was analysed by Cole-Cole plots. The activation energy follows the Arrhenius law and is found to decrease with increasing frequency for each composition. The frequency dependence of ac conductivity follows the u...
Magnesium hydrogen phosphate (MHP) and transition metal doped cadmium magnesium hydrogen phosphat... more Magnesium hydrogen phosphate (MHP) and transition metal doped cadmium magnesium hydrogen phosphate (CdMHP) was synthesized in the form of crystalline material by room temperature solution technique known as gel encapsulation technique. The synthesized crystals were then characterized for their structural, mechanical and electrical investigations using various chemical and physical methods. X-ray diffraction analysis (XRD) establishes magnesium hydrogen phosphate and cadmium magnesium hydrogen phosphate belonging to orthorhombic crystal system with space group Pbca. The mechanical behaviour of these crystals was studied by calculating Vicker's hardness number. The behaviour of microhardness with applied load was observed to be complex. The electrical behaviour was carried out by calculating dielectric constant at different temperatures and for different frequencies. The dielectric constant (ε /) was found to be strongly dependent on temperature and frequency. The transition metal doping of cadmium in magnesium hydrogen phosphate remarkably decrease the value of dielectric constant from 68 to 23. The transition temperature also decreases from 330˚C in case of magnesium hydrogen phosphate to 310˚C in case of cadmium magnesium hydrogen phosphate.
Abstract Lead nickel niobate–lead zirconate titanate (PNNZT) and cadmium doped (CdPNNZT) with gen... more Abstract Lead nickel niobate–lead zirconate titanate (PNNZT) and cadmium doped (CdPNNZT) with general composition Pb 1.0 (Ni 0.167 Nb 0.333 Zr 0.155 Ti 0.345 )O 3 (PNNZT), Pb 0.98 Cd 0.02 (Ni 0.167 Nb 0.333 Zr 0.155 Ti 0.345 )O 3 (CdPNNZT) respectively were prepared by conventional solid state reaction. Microstructural and compositional analyses have been carried out by X-ray diffraction and scanning electron microscopy. With cadmium doping there is an increase in both the perovskite phase and in grain size. The effect of cadmium doping on the structural and dielectric properties has been investigated. An increase in the dielectric constant was observed with cadmium doping in PNNZT. Complex impedance analysis suggests poly-dispersive non-Debye type relaxation to occur in the material. The frequency dependence of AC conductivity obeys the universal double power law. The value of activation energy depends on increase in frequency as well as on cadmium doping.
Samarium doped calcium hydrogen phosphate was synthesized as single crystal by room temperature s... more Samarium doped calcium hydrogen phosphate was synthesized as single crystal by room temperature solution growth technique, namely, silica gel technique. The kinetics of the growth parameters was studied with regard to variation of pH, dopant concentration, gel ageing, and upper reactant concentration. The optimum conditions for the growth of good quality single crystal were worked out. Single crystal X-ray diffraction analysis establishes that the crystal belongs to monoclinic system. The density observed by the flotation method is greater than the density of the reported pure calcium hydrogen phosphate thereby suggesting the incorporation of the dopant (Sm) ion into the lattice of host (CHP). Thermal analysis gave two sharp endothermic peaks which are due to partial dehydration and phase transition, respectively. Dielectric studies establish a shift in the Curie temperature from 355 to 370°C only at higher frequencies thereby suggesting the relaxational behavior of the material.
The solid solutions of lead nickel niobate (PNN) and lead zirconate titanate (PZT), with general ... more The solid solutions of lead nickel niobate (PNN) and lead zirconate titanate (PZT), with general formula 0.5 Pb(NixNb1-x)O3-0.5 PZT, where x = 1/3, 1/2 and 2/3 and Zr/Ti = 50/50, were prepared by conventional solid state reaction technique. The perovskite phase formation and morphology were examined by powder X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques. From microstructure investigations, the grain size was found to lie in the range of 0.2-1.1 ?m. Diffuse phase transition and dielectric relaxation was obtained for all three compositions. The nature of dielectric relaxation was investigated through complex plane Argand plot or Cole-Cole plot. It was found that both grains as well as grain boundary contribute to dielectric relaxation. A direct correlation between the grain size and electrical properties was obtained. The remnant polarization and grain size were found to follow the inverse relationship. The inverse relationship between remnant polarization...
The Type Three Secretion System (T3SS), or injectisome, is a macromolecular infection machinery p... more The Type Three Secretion System (T3SS), or injectisome, is a macromolecular infection machinery present in many pathogenic Gram-negative bacteria. It consists of a basal body, anchored in both bacterial membranes, and a hollow needle through which effector proteins are delivered into the target host cell. Two different architectures of the T3SS needle have been previously proposed. First, an atomic model of the Salmonella typhimurium needle was generated from solid-state NMR data. The needle subunit protein, PrgI, comprises a rigid-extended N-terminal segment and a helix-loop-helix motif with the N-terminus located on the outside face of the needle. Second, a model of the Shigella flexneri needle was generated from a high-resolution 7.7-Å cryo-electron microscopy density map. The subunit protein, MxiH, contains an Nterminal a-helix, a loop, another a-helix, a 14-residue-long b-hairpin (Q51-Q64) and a C-terminal a-helix, with the Nterminus facing inward to the lumen of the needle. In the current study, we carried out solid-state NMR measurements of wild-type Shigella flexneri needles polymerized in vitro and identified the following secondary structure elements for MxiH: a rigid-extended N-terminal segment (S2-T11), an a-helix (L12-A38), a loop (E39-P44) and a C-terminal a-helix (Q45-R83). Using immunogold labeling in vitro and in vivo on functional needles, we located the N-terminus of MxiH subunits on the exterior of the assembly, consistent with evolutionary sequence conservation patterns and mutagenesis data. We generated a homology model of Shigella flexneri needles compatible with both experimental data: the MxiH solid-state NMR chemical shifts and the state-of-the-art cryoEM density map. These results corroborate the solid-state NMR structure previously solved for Salmonella typhimurium PrgI needles and establish that Shigella flexneri and Salmonella typhimurium subunit proteins adopt a conserved structure and orientation in their assembled state. Our study reveals a common structural architecture of T3SS needles, essential to understand T3SS-mediated infection and develop treatments.
The Type Three Secretion System (T3SS), or injectisome, is a macromolecular infection machinery p... more The Type Three Secretion System (T3SS), or injectisome, is a macromolecular infection machinery present in many pathogenic Gram-negative bacteria. It consists of a basal body, anchored in both bacterial membranes, and a hollow needle through which effector proteins are delivered into the target host cell. Two different architectures of the T3SS needle have been previously proposed. First, an atomic model of the Salmonella typhimurium needle was generated from solid-state NMR data. The needle subunit protein, PrgI, comprises a rigid-extended N-terminal segment and a helix-loop-helix motif with the N-terminus located on the outside face of the needle. Second, a model of the Shigella flexneri needle was generated from a high-resolution 7.7-Å cryo-electron microscopy density map. The subunit protein, MxiH, contains an Nterminal a-helix, a loop, another a-helix, a 14-residue-long b-hairpin (Q51-Q64) and a C-terminal a-helix, with the Nterminus facing inward to the lumen of the needle. In the current study, we carried out solid-state NMR measurements of wild-type Shigella flexneri needles polymerized in vitro and identified the following secondary structure elements for MxiH: a rigid-extended N-terminal segment (S2-T11), an a-helix (L12-A38), a loop (E39-P44) and a C-terminal a-helix (Q45-R83). Using immunogold labeling in vitro and in vivo on functional needles, we located the N-terminus of MxiH subunits on the exterior of the assembly, consistent with evolutionary sequence conservation patterns and mutagenesis data. We generated a homology model of Shigella flexneri needles compatible with both experimental data: the MxiH solid-state NMR chemical shifts and the state-of-the-art cryoEM density map. These results corroborate the solid-state NMR structure previously solved for Salmonella typhimurium PrgI needles and establish that Shigella flexneri and Salmonella typhimurium subunit proteins adopt a conserved structure and orientation in their assembled state. Our study reveals a common structural architecture of T3SS needles, essential to understand T3SS-mediated infection and develop treatments.
Lead niobate zirconate titanate (PNZT) with general formula 0.5PbNb2O6–0.5Pb(ZrxTi1-x)O3 (where x... more Lead niobate zirconate titanate (PNZT) with general formula 0.5PbNb2O6–0.5Pb(ZrxTi1-x)O3 (where x = 0.15, 0.25, 0.35) and lead nickel niobate zirconate titanate (PNNZT) with general formula Pb(NixNb0.5-xZr0.25Ti0.25)O3 (where x = 0.167, 0.250, 0.333) have been prepared by conventional solid state reaction. The phase formation has been studied by X – ray diffraction analysis. Raman investigations have been carried out in the 200–1000 cm−1 wave number range. The structural changes observed in the X – ray diffraction pattern has been further confirmed by Raman analysis. The major changes in the E(1TO), A1(1TO) and E+B1 phonon modes suggest the structural change from cubic to rhombohedral with increase in Ni concentration in PNNZT. The optical band gap has been calculated from UV – Vis absorption spectra. Keywords PNZT . X-ray diffraction . Raman spectra . Absorption spectra . Band gap
Rare earth double doped lead titanate with general formula Pb 1-x Pr x Ti 1-y Y y O 3 where x (pr... more Rare earth double doped lead titanate with general formula Pb 1-x Pr x Ti 1-y Y y O 3 where x (praseodymium) = 0.02, 0.04, 0.06, 0.08 and y (yttrium) = 0.02 was synthesized by solid state reaction technique. X-ray diffraction analysis confirms single phase formation with perovskite structure having tetragonal phase. Micro-structural analysis shows formation of dense micro-structure with grain size calculated using average line intercepted method. Dielectric behavior as a function of temperature was found to decrease with Pr substitution. The diffusivity in the dielectric behavior was observed in all the compositions. Piezoelectric coefficient d 33 and g 33 was determined with increase in compositions of Pr substituent. The ferroelectric property was observed at room temperature and the value of remanent polarization (P r), spontaneous polarization (P s) and (E C) coercive field was calculated.
Pure and cerium mixed neodymium orthophosphate was synthesized as nanoparticles via wet chemical ... more Pure and cerium mixed neodymium orthophosphate was synthesized as nanoparticles via wet chemical co-precipitation technique. Powder X-ray diffraction (PXRD) study suggests that the average crystallite size and X-ray density decreases with the mixing of cerium in neodymium orthophosphate. Scanning electron microscope (SEM) and transmission electron microscope (TEM) studies revealed spherical morphology for neodymium orthophosphate but when cerium is mixed the morphology changes into rectangular platelet, like nanorods. Fourier transform infrared (FTIR) spectroscopy signifies slightly shifting of bands towards lower wave number and the force constant were also calculated. Thermal analysis suggests that the material get stabilized after 425 C and structural phase transition was seen above 800 C. Optical absorption spectrum give various absorption bands corresponding to each wavelength revealing transitions of Nd 3þ and Ce 3þ present in the UV-VIS region and optical band gap energy decreases from 3.3 to 2.4 eV. Mixing of cerium in neodymium orthophosphate enhances the value of dielectric constant and decreases the transition temperature. The value of exponent 'n' suggest that in neodymium orthophosphate, conduction is through hopping mechanism but for cerium neodymium orthophosphate conduction correspond to long range diffusion of ions.
A B S T R A C T Cerium orthovanadate, neodymium orthovanadate and mixed cerium neodymium orthovan... more A B S T R A C T Cerium orthovanadate, neodymium orthovanadate and mixed cerium neodymium orthovanadate nanoparticles was prepared by co-precipitation method. Powder X-ray diffraction reveals tetragonal zircon structure. Slight increase in lattice parameter, volume and decrease in X-ray density inferred that Ce 3+ and Nd 3+ ion replaces each other. Transmission electron microscopy suggests change in morphology with the effect of mixing and validates formation of nanocrystalline material. The infrared transmittance spectrum confirmed the presence of various functional groups. Dielectric properties as function of frequency show dielectric constant and loss tangent decreases with increase in frequency which is due to Maxwell–Wagner type interfacial polarization. The variation of AC conductivity measurement with frequency suggests conduction mechanism due to large polaron hopping in CeV whereas small polaron in mixed CeNdV. The activation energy decreases with rising frequency indicates the conduction mechanism is based on polaron hopping between localized states in disordered manner.
A ternary system of lead niobate–lead zirconate–lead titanate with composition xPN–yPZ–(x-y)PT wh... more A ternary system of lead niobate–lead zirconate–lead titanate with composition xPN–yPZ–(x-y)PT where í µí±¥ = 0.5 and í µí±¦ = 0.15, 0.25, and 0.35 known as PNZT has been prepared by conventional mixed oxide route at a temperature of 1100 ∘ C. The formation of the perovskite phase was established by X-ray diffraction analysis. The surface morphology studied by scanning electron microscopy shows the formation of fairly dense grains and elemental composition was confirmed by energy dispersive X-ray analysis. Dielectric properties like dielectric constant and dielectric loss (í µí¼ í® í° and tan í µí»¿) indicate poly-dispersive nature of the material. The temperature dependent dielectric constant (í µí¼ í® í°) curve indicates relaxor behaviour with two dielectric anomalies. The poly-dispersive nature of the material was analysed by Cole-Cole plots. The activation energy follows the Arrhenius law and is found to decrease with increasing frequency for each composition. The frequency dependence of ac conductivity follows the universal power law. The ac conductivity analysis suggests that hopping of charge carriers among the localized sites is responsible for electrical conduction. The ferroelectric studies reveal that these ternary systems are soft ferroelectric.
the similar trend, suggesting the temperature dependent dielectric relaxation. The Cr doping enha... more the similar trend, suggesting the temperature dependent dielectric relaxation. The Cr doping enhances the dielectric properties of GdMnO 3 . The room temperature magnetic behaviour analyzed from the magnetic field dependent magnetization curves suggests paramagnetic behavior for both the composition; however Cr doping does enhance the magnetization.
The solid solutions of lead nickel niobate (PNN) and lead zirconate titanate (PZT), with general ... more The solid solutions of lead nickel niobate (PNN) and lead zirconate titanate (PZT), with general formula 0.5 Pb(NixNb1-x)O3-0.5 PZT, where x = 1/3, 1/2 and 2/3 and Zr/Ti = 50/50, were prepared by conventional solid state reaction technique. The perovskite phase formation and morphology were examined by powder X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques. From microstructure investigations, the grain size was found to lie in the range of 0.2–1.1 μm. Diffuse phase transition and dielectric relaxation was obtained for all three compositions. The nature of dielectric relaxation was investigated through complex plane Argand plot or Cole-Cole plot. It was found that both grains as well as grain boundary contribute to dielectric relaxation. A direct correlation between the grain size and electrical properties was obtained. The remnant polarization and grain size were found to follow the inverse relationship. The inverse relationship between remnant polarization and grain size was established.
Samarium doped calcium hydrogen phosphate was synthesized as single crystal by room temperature s... more Samarium doped calcium hydrogen phosphate was synthesized as single crystal by room temperature solution growth technique, namely, silica gel technique.The kinetics of the growth parameters was studiedwith regard to variation of pH, dopant concentration, gel ageing, and upper reactant concentration. The optimum conditions for the growth of good quality single crystal were worked out. Single crystal X-ray diffraction analysis establishes that the crystal belongs to monoclinic system.The density observed by the flotation method is greater than the density of the reported pure calciumhydrogen phosphate thereby suggesting the incorporation of the dopant (Sm) ion into the lattice of host (CHP). Thermal analysis gave two sharp endothermic peaks which are due to partial dehydration and phase transition, respectively. Dielectric studies establish a shift in the Curie temperature from 355 to 370∘C only at higher frequencies thereby suggesting the relaxational behavior of the material.
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Papers by Rashmi Gupta
lead nickel niobate zirconate titanate (PNNZT) with general formula Pb(NixNb0.5-xZr0.25Ti0.25)O3 (where x = 0.167, 0.250,
0.333) have been prepared by conventional solid state reaction. The phase formation has been studied by X – ray diffraction
analysis. Raman investigations have been carried out in the 200–1000 cm−1 wave number range. The structural changes observed
in the X – ray diffraction pattern has been further confirmed by Raman analysis. The major changes in the E(1TO), A1(1TO) and
E+B1 phonon modes suggest the structural change from cubic to rhombohedral with increase in Ni concentration in PNNZT.
The optical band gap has been calculated from UV – Vis absorption spectra.
Keywords PNZT . X-ray diffraction . Raman spectra . Absorption spectra . Band gap
Pb1.0(Ni0.167Nb0.333Zr0.155Ti0.345)O3 (PNNZT), Pb0.98Cd0.02(Ni0.167Nb0.333Zr0.155Ti0.345)O3 (CdPNNZT) respectivelywerepreparedbyconven-
tional solidstatereaction.MicrostructuralandcompositionalanalyseshavebeencarriedoutbyX-raydiffractionandscanningelectron
microscopy. Withcadmiumdopingthereisanincreaseinboththeperovskitephaseandingrainsize.Theeffectofcadmiumdopingonthe
structural anddielectricpropertieshasbeeninvestigated.AnincreaseinthedielectricconstantwasobservedwithcadmiumdopinginPNNZT.
Complex impedanceanalysissuggestspoly-dispersivenon-Debyetyperelaxationtooccurinthematerial.ThefrequencydependenceofAC
conductivity obeys the universal doublepowerlaw.Thevalueofactivationenergydependsonincreaseinfrequencyaswellasoncadmium
doping.
0.5 Pb(NixNb1-x)O3-0.5 PZT, where x = 1/3, 1/2 and 2/3 and Zr/Ti = 50/50, were prepared by conventional solid
state reaction technique. The perovskite phase formation and morphology were examined by powder X-ray
diffraction (XRD) and scanning electron microscopy (SEM) techniques. From microstructure investigations,
the grain size was found to lie in the range of 0.2–1.1 μm. Diffuse phase transition and dielectric relaxation
was obtained for all three compositions. The nature of dielectric relaxation was investigated through complex
plane Argand plot or Cole-Cole plot. It was found that both grains as well as grain boundary contribute to
dielectric relaxation. A direct correlation between the grain size and electrical properties was obtained. The
remnant polarization and grain size were found to follow the inverse relationship. The inverse relationship
between remnant polarization and grain size was established.
namely, silica gel technique.The kinetics of the growth parameters was studiedwith regard to variation of pH, dopant concentration,
gel ageing, and upper reactant concentration. The optimum conditions for the growth of good quality single crystal were worked
out. Single crystal X-ray diffraction analysis establishes that the crystal belongs to monoclinic system.The density observed by the
flotation method is greater than the density of the reported pure calciumhydrogen phosphate thereby suggesting the incorporation
of the dopant (Sm) ion into the lattice of host (CHP). Thermal analysis gave two sharp endothermic peaks which are due to partial
dehydration and phase transition, respectively. Dielectric studies establish a shift in the Curie temperature from 355 to 370∘C only
at higher frequencies thereby suggesting the relaxational behavior of the material.
lead nickel niobate zirconate titanate (PNNZT) with general formula Pb(NixNb0.5-xZr0.25Ti0.25)O3 (where x = 0.167, 0.250,
0.333) have been prepared by conventional solid state reaction. The phase formation has been studied by X – ray diffraction
analysis. Raman investigations have been carried out in the 200–1000 cm−1 wave number range. The structural changes observed
in the X – ray diffraction pattern has been further confirmed by Raman analysis. The major changes in the E(1TO), A1(1TO) and
E+B1 phonon modes suggest the structural change from cubic to rhombohedral with increase in Ni concentration in PNNZT.
The optical band gap has been calculated from UV – Vis absorption spectra.
Keywords PNZT . X-ray diffraction . Raman spectra . Absorption spectra . Band gap
Pb1.0(Ni0.167Nb0.333Zr0.155Ti0.345)O3 (PNNZT), Pb0.98Cd0.02(Ni0.167Nb0.333Zr0.155Ti0.345)O3 (CdPNNZT) respectivelywerepreparedbyconven-
tional solidstatereaction.MicrostructuralandcompositionalanalyseshavebeencarriedoutbyX-raydiffractionandscanningelectron
microscopy. Withcadmiumdopingthereisanincreaseinboththeperovskitephaseandingrainsize.Theeffectofcadmiumdopingonthe
structural anddielectricpropertieshasbeeninvestigated.AnincreaseinthedielectricconstantwasobservedwithcadmiumdopinginPNNZT.
Complex impedanceanalysissuggestspoly-dispersivenon-Debyetyperelaxationtooccurinthematerial.ThefrequencydependenceofAC
conductivity obeys the universal doublepowerlaw.Thevalueofactivationenergydependsonincreaseinfrequencyaswellasoncadmium
doping.
0.5 Pb(NixNb1-x)O3-0.5 PZT, where x = 1/3, 1/2 and 2/3 and Zr/Ti = 50/50, were prepared by conventional solid
state reaction technique. The perovskite phase formation and morphology were examined by powder X-ray
diffraction (XRD) and scanning electron microscopy (SEM) techniques. From microstructure investigations,
the grain size was found to lie in the range of 0.2–1.1 μm. Diffuse phase transition and dielectric relaxation
was obtained for all three compositions. The nature of dielectric relaxation was investigated through complex
plane Argand plot or Cole-Cole plot. It was found that both grains as well as grain boundary contribute to
dielectric relaxation. A direct correlation between the grain size and electrical properties was obtained. The
remnant polarization and grain size were found to follow the inverse relationship. The inverse relationship
between remnant polarization and grain size was established.
namely, silica gel technique.The kinetics of the growth parameters was studiedwith regard to variation of pH, dopant concentration,
gel ageing, and upper reactant concentration. The optimum conditions for the growth of good quality single crystal were worked
out. Single crystal X-ray diffraction analysis establishes that the crystal belongs to monoclinic system.The density observed by the
flotation method is greater than the density of the reported pure calciumhydrogen phosphate thereby suggesting the incorporation
of the dopant (Sm) ion into the lattice of host (CHP). Thermal analysis gave two sharp endothermic peaks which are due to partial
dehydration and phase transition, respectively. Dielectric studies establish a shift in the Curie temperature from 355 to 370∘C only
at higher frequencies thereby suggesting the relaxational behavior of the material.