Lead-free ceramics (1 À x)(K 0.48 Na 0.52)NbO 3-(x/5.15)K 2.9 Li 1.95 Nb 5.15 O 15.3 (x = 0.3-0.6... more Lead-free ceramics (1 À x)(K 0.48 Na 0.52)NbO 3-(x/5.15)K 2.9 Li 1.95 Nb 5.15 O 15.3 (x = 0.3-0.6, KNN-KLN100x) were prepared by conventional sintering technique at a low temperature of 960 8C. The effects of KLN contents on microstructure, dielectric, and piezoelectric properties were investigated. After the addition of KLN, the sintering performance and Curie temperature of the ceramics were markedly improved. The ceramics with x = 0.3 exhibited very good piezoelectric properties: d 33 = 138 pC/N, k p = 45.03%, T c = 495 8C, the dielectric constant at room temperature e r (RT) = 478 and the maximum dielectric constant e r (max) = 5067. These results indicated that the KNN-KLN100x lead-free ceramics sintered at low temperatures are promising for high temperature piezoelectric applications.
Temperature dependent X-ray diffraction (XRD) and dielectric properties of perovskite Ba(Zr[Formu... more Temperature dependent X-ray diffraction (XRD) and dielectric properties of perovskite Ba(Zr[Formula: see text]Ti[Formula: see text]O3ceramic prepared using a standard solid-state reaction process is presented. Along with phase transitions at low temperature, a new phase transition at high temperature (873[Formula: see text]C at 20[Formula: see text]Hz), diffusive in character has been found where the lattice structure changes from monoclinic (space group: [Formula: see text] to hexagonal (space group: [Formula: see text]). This result places present ceramic in the list of potential candidate for intended high temperature applications. The AC conductivity data followed hopping type charge conduction and supports jump relaxation model. The experimental value of [Formula: see text][Formula: see text]pC/N was found. The dependence of polarization and strain on electric field at room temperature suggested that lead-free Ba(Zr[Formula: see text]Ti[Formula: see text]O3is a promising materi...
Lead-free Ba(In0.5Nb0.5)1-xTixO3 (0 ? x ? 1) ceramics was synthesized using a standard high tempe... more Lead-free Ba(In0.5Nb0.5)1-xTixO3 (0 ? x ? 1) ceramics was synthesized using a standard high temperature solidstate reaction method and sintered at 1400?C/4 h (except the pure BaTiO3 which was sintered at 1300?C/4 h). The ceramics was characterized by X-ray diffraction, scanning electron microscopy, dielectric, impedance and AC conductivity studies. The crystal structure of the compounds was found to be cubic (with the space group Pm3m) for x = 0,0.25 and 0.50 and tetragonal (P4/mmm) for x = 0.75 and 1.0. Increase in Ti-content in the ceramic samples leads to the decrease in unit cell volume while the values of real as well as imaginary parts of dielectric constant and AC conductivity increase. Complex impedance spectroscopy analysis indicated the negative temperature coefficient of resistance. AC conductivity data supported the hopping type of conduction in the system and obeyed Jonscher?s power law. The real and imaginary parts of dielectric constant and AC conductivity data fit ex...
Lead-free [Formula: see text](0.50(Ba[Formula: see text]Ca[Formula: see text]TiO3–0.50Ba(Zr[Formu... more Lead-free [Formula: see text](0.50(Ba[Formula: see text]Ca[Formula: see text]TiO3–0.50Ba(Zr[Formula: see text]Ti[Formula: see text]O[Formula: see text]-([Formula: see text]PVDF ceramic–polymer nanocomposites with [Formula: see text], 0.05, 0.10, 0.15, 0.20, 0.25 were prepared using melt-mixing technique. The distribution of nanoceramic filler particles (0.50(Ba[Formula: see text]Ca[Formula: see text]TiO3–0.50Ba(Zr[Formula: see text]Ti[Formula: see text]O[Formula: see text] in the PVDF matrix were examined using scanning electron microscope. Impedance analysis indicated the negative temperature coefficient of resistance character of all the test specimens. Filler concentration-dependent piezoelectric coefficient ([Formula: see text] data followed exponential growth types of variation. The data for ac conductivity were found to obey Jonscher’s power law. The correlated barrier hopping (CBH) model was found to explain the mechanism of charge transport occurring in the system. The low v...
In this work, lead-free Na 0.4 Bi 0.5 TiO 3-K 0.1 Bi 0.5 TiO 3 (NKBT) piezoelectric ceramics were... more In this work, lead-free Na 0.4 Bi 0.5 TiO 3-K 0.1 Bi 0.5 TiO 3 (NKBT) piezoelectric ceramics were prepared by the solid-state reaction method and their structural, ferroelectric and dielectric properties were systematically studied. NKBT sintered at 1150˚C for 4 h exhibited highly dense (96%-98% of the theoretical density) and uniform grains of size 1.1 μm. The coexistence of tetragonal (P4bm) and rhombohedral (R3c) phases due to the presence of morphotrophic phase boundary for the chosen composition has been confirmed by the Rietveld refinement studies. Enhanced ferroelectric properties such as remnant polarization (P r) and coercive field (E C) are found to be 37 μC/cm 2 and 30 kV/cm, respectively. The optimized synthesis procedure for NKBT ceramics resulted in enhanced strain (%) and converse piezoelectric coefficient (d 33 *) of 0.3 % and 554 pm/V which is attributed to smaller grain size and switching of non 180˚ domains. NKBT ceramics with such excellent piezoelectric properties can be considered as a promising candidate for actuator applications.
An eco-friendly lactobacillus sp. (microbe) assisted synthesis of titanium nanoparticles is repor... more An eco-friendly lactobacillus sp. (microbe) assisted synthesis of titanium nanoparticles is reported. The synthesis is performed at room temperature. X-ray and transmission electron microscopy analyses are performed to ascertain the formation of Ti nanoparticles. Individual nanoparticles as well as a number of aggregates almost spherical in shape having a size of 40-60 nm are found.
Extremely small amounts of La and Al doping on the A and B site of BaTiO 3 , respectively, result... more Extremely small amounts of La and Al doping on the A and B site of BaTiO 3 , respectively, resulting in a solid solution of the type Ba 1-3x La 2x Ti 1-3x Al 4x O 3 have been investigated. The compositions have been prepared by the Pechini process. The x-ray diffraction ͑XRD͒ reveals the presence of tetragonal ͑P4/mmm͒ phase. The XRD data has been analyzed using FULLPROF, a Rietveld refinement package. The compositions have been characterized by dielectric spectroscopy between room temperature and 200°C. The resulting compounds ͑0 ഛ x ഛ 0.008͒ exhibit a remarkable decrease in the Curie temperature as well as a significant enhancement of the dielectric constant.
Polycrystalline (Na 0.5 Sb 0.5)TiO 3 was prepared using a high-temperature solid-state reaction m... more Polycrystalline (Na 0.5 Sb 0.5)TiO 3 was prepared using a high-temperature solid-state reaction method. An XRD analysis indicated the formation of a single-phase monoclinic structure. Complex impedance studies revealed the presence of grain boundary effects from 300 • C onwards. Also, the dielectric relaxation in the system was found to be of a non-Debye type. The ac conductivity data were used to evaluate the density of states at the Fermi level, the minimum hopping length and activation energy of the compound. The dc electrical and thermal conductivities of grain and grain boundary have been assessed. The correlated barrier hopping model was found to successfully explain the mechanism of charge transport in (Na 0.5 Sb 0.5)TiO 3 .
In this contribution, the structural, electrical, dielectric, and microstructural properties of d... more In this contribution, the structural, electrical, dielectric, and microstructural properties of double perovskite Gd 2 NiMnO 6 doped with strontium were presented. The strontium-doped double perovskite Gd 2-x Sr x NiMnO 6 (x = 0, 0.1 & 0.3) was synthesized by using the solid-state reaction method. The X-ray diffraction and scanning electron microscopy characterization techniques were used to investigate the structural and surface morphological properties. The Rietveld refinement depicted the formation of pure phase having a P21/n monoclinic space group. A decrease in grain size and crystallite size was found with the dopant concentration increase, resulted in enhancement of dielectric constant of the material. The frequency-and temperature-dependent dielectric study revealed increase in dielectric constant and decrease in dielectric loss with the increase in dopant concentration. Apart from dielectric studies, the conductivity studies revealed decrease in conductivity with the increase in Sr doping, supporting the dielectric properties. In conclusion, the synthesized material is functional, has high dielectric constant, low dielectric losses and low conductivity, and, hence, it can be considered as a potential candidate for high k dielectric materials.
We demonstrate the potential of dopamine modified 0.5(Ba0.7Ca0.3)TiO3-0.5Ba(Zr0.2Ti0.8)O3 filler ... more We demonstrate the potential of dopamine modified 0.5(Ba0.7Ca0.3)TiO3-0.5Ba(Zr0.2Ti0.8)O3 filler incorporated polyvinylidene fluoride (PVDF) composite prepared by solution cast method as both flexible energy storage and harvesting devices. The introduction of dopamine in filler surface functionalization acts as bridging elements between filler and polymer matrix and results in a better filler dispersion and an improved dielectric loss tangent (<0.02) along with dielectric permittivity ranges from 9 to 34 which is favorable for both energy harvesting and storage. Additionally, a significantly low DC conductivity (< 10-9 ohm-1 cm-1) for all composites was achieved leading to an improved breakdown strength and charge accumulation capability. Maximum breakdown strength of 134 KV/mm and corresponding energy storage density 0.72 J/cm 3 were obtained from the filler content 10 weight%. The improved energy harvesting performance was characterized by obtaining a maximum piezoelectric charge constant (d33) = 78 pC/N, and output voltage (Vout) = 0.84 V along with maximum power density of 3.46 µW/cm 3 for the filler content of 10 wt%. Thus, the results show 0.5(Ba0.7Ca0.3)TiO3-0.5Ba(Zr0.2Ti0.8)O3/PVDF composite has the potential for energy storage and harvesting applications simultaneously that can significantly suppress the excess energy loss arises while utilizing different material.
Temperature-dependent dielectric permittivity of lead-free (Li x Na 1-x)NbO 3 for nominal x = 0.0... more Temperature-dependent dielectric permittivity of lead-free (Li x Na 1-x)NbO 3 for nominal x = 0.04-0.20, prepared by solid state reaction followed by sintering, was studied to resolve often debated issue pertaining to exactness of morphotropic phase boundary (MPB) location along with structural aspects and phase stability in the system near MPB. Interestingly, a diffuse phase transition has been observed in the dielectric permittivity peak arising from the disorder induced in A-site and structural frustration in the perovskite cell due to Li substitution. A partial phase diagram has been proposed based on temperature-dependent dielectric permittivity studies. The room temperature piezoelectric and ferroelectric properties were investigated and the ceramics with x = 0.12 showed relatively good electrical properties (d 33 = 28 pC/N, k p = 13.8%, Q m = 440, P r = 12.5 μC/cm 2 , E C = 43.2 kV/cm, T m = 340 o C). These parameter values make this material suitable for piezoelectric resonator and filter applications. Moreover, a high dielectric permittivity (εʹ r = 2703) with broad diffuse peak near transition temperature along with low dielectric loss (< 4%) in a wide temperature range (50-250 o C) found in this material may also have a potential 2 application in high-temperature multilayer capacitors in automotive and aerospace related industries.
For the last few years fast ion conducting lithium glasses are being studied due to their potenti... more For the last few years fast ion conducting lithium glasses are being studied due to their potential use in advanced electrochemical devices. A number of glass systems containing oxides, sulphides and other lithium compounds prepared by both conventional cooling and rapid quenching techniques have been reported. In this paper we review the transport properties of lithium ion conducting glasses. The special features of the ionic conduction process have been highlighted and some experimental techniques to study transport properties have been described. Some of the common observations of the properties have been discussed and finally some important problems for future development have been pointed out.
Impedance and electrical conduction studies of Ba(Pr 1/2 Nb 1/2)O 3 ceramic prepared through conv... more Impedance and electrical conduction studies of Ba(Pr 1/2 Nb 1/2)O 3 ceramic prepared through conventional ceramic fabrication technique are presented. The crystal symmetry, space group and unit cell dimensions were estimated using Rietveld analysis. X-ray diffraction analysis indicated the formation of a single-phase cubic structure with space group, P m3m. EDAX and SEM studies were carried out to study the quality and purity of compound. To find a correlation between the response of the real system and idealized model circuit composed of discrete electrical components, the model fittings were presented using impedance data. Complex impedance as well as electric modulus analyses suggested dielectric relaxation to be of non-Debye type and negative temperature coefficient of resistance character. The correlated barrier hopping model was employed to successfully explain the mechanism of charge transport in Ba(Pr 1/2 Nb 1/2)O 3. The a.c. conductivity data were used to evaluate density of states at Fermi level, minimum hopping length and apparent activation energy.
The homogeneous dispersion of carbon nanotubes (CNT) remains a hindrance in exploiting the except... more The homogeneous dispersion of carbon nanotubes (CNT) remains a hindrance in exploiting the exceptional properties associated with CNT in polymer/CNT composites. Here we present for the first time the key role of sodium salt of 6-aminohexanoic acid (Na-AHA) in assisting debundling the multiwall carbon nanotubes (MWNT) through specific interactions leading to homogeneous dispersion within polyamide6 (PA6) matrix during melt-mixing. The composite fabricated via this route exhibits low electrical percolation threshold of 0.5 wt% at room temperature, the lowest reported value in this system so far. FTIR and Raman spectroscopy reveal the existence of 'cation-p' interaction between Na-AHA and MWNT. The phenomenon of reactive coupling between amine functionality of Na-AHA and acid end group of PA6 during melt-mixing is also established.
New fluoride glasses in the system PbF2-MnF2-AI(PO3) a have been synthesised and found o to have ... more New fluoride glasses in the system PbF2-MnF2-AI(PO3) a have been synthesised and found o to have high d.c. conductivities, presumably due t6mobileF ions. A.C. electrical data (25-200 C) have been analyzed by impedance spectroscopy. A glass with the composition 85PbF2-5MnF 2-10AI(PO3) 3 yields a record value for conductivity in an anionic conducting glass, c200 = 1.1 × 10~(f~-cm)-1, nearly two orders of magnitude higher than the best values so far reported. Electrical and mechanical relaxation data have been compared in the isofrequency-inverse temperature representation. As seen previously for cation conductors, the mechanical relaxation is less exponential (broader) than the electrical relaxation. However, in the present case the most probable mechanical relaxation time is shorter than the most probable electrical relaxation time. MATERIALS INDEX-Fluoride glasses
International Journal of Green Nanotechnology: Physics and Chemistry
A low-cost, green, and highly reproducible microbe (Lactobacillus sp.)-mediated biosynthesis of G... more A low-cost, green, and highly reproducible microbe (Lactobacillus sp.)-mediated biosynthesis of Gd 2 O 3 nanoparticles is reported. X-ray and transmission electron microscopy analyses were performed to ascertain the formation of Gd 2 O 3 nanoparticles. X-ray analysis indicated that Gd 2 O 3 nanoparticles have a body-centered cubic (BCC) unit cell structure. Individual nanoparticles almost spherical in shape of 10-20 nm were found. An effort has been made to understand the possible involved mechanism for the biosynthesis of Gd 2 O 3 nanoparticles. The present procedure offers the benefit of eco-friendliness and amenability for large-scale production through scaling up.
A simple and rapid quenching apparatus has been designed and fabricated. The limit of glass forma... more A simple and rapid quenching apparatus has been designed and fabricated. The limit of glass formation in the system LiF-LiaO-Al(POa)a could be expanded by rapid quenching with this arrangement. The electrical conductivity of rapidly quenched glasses derived from complex impedance/admittance analysis are higher and the activation energy are lower compared to conventionally prepared glasses of corresponding chemical compositions. Annealing of the "as quenched" glasses causes considerable reduction in conductivity.
International Conference on Advanced Nanomaterials & Emerging Engineering Technologies, 2013
Phase pure (T'-type, sp. gpo I4/mmm), category of materials to be explored fully for their dielec... more Phase pure (T'-type, sp. gpo I4/mmm), category of materials to be explored fully for their dielectric nanocrystalline Gd2Cu04 powders were synthesized by a wet properties. However, the observed high £/ was contested to be chemical citrate gel complexation process known as "Pechini process". The T'-type phase was realized at much lower (_ 1073 mostly intrinsic in nature and extrinsic factors affecting £/ K) temperature than those reported for conventional ceramic were not studied. Further, these few select compounds studied powder mixing and solid state reaction process (_ 1223 K). The so far were synthesized using standard ceramic powder average particle size of the solid state reacted particles from HR-mixing and solid state reaction process, which requires high TEM was found to be-50 nm. The dielectric studies on the synthesis temperatures and often encountered with Gd2Cu04 pellets revealed extremely high values of E/ (�10 4) inhomogeneity of constituent ions. In contrast, wet chemical over the measure frequencies (1 <5. f <5. 1 MHz) and temperature synthesis process facilitates the molecular level mixing of (173 K <5. T<5. 423 K) ranges. Being non-ferroelectric, we propose constituent elements, which in turn contribute towards such high values of E/ arise due to an Internal barrier layer maintaining better stoichiometry and lower synthesis capacitance effect, formed by insulating grain boundaries and semiconducting grains in the ceramics. temperatures [7]. However, there have been a very few reports Keywords-Pechni process, T'-cuprate, giant dielectric on wet chemical synthesis of T'-type cuprates, including constant. GdzCu04 [8]. Hence, alternate method of synthesis of T'-type cuprate, viz. wet chemical process seems an interesting
Lead-free ceramics (1 À x)(K 0.48 Na 0.52)NbO 3-(x/5.15)K 2.9 Li 1.95 Nb 5.15 O 15.3 (x = 0.3-0.6... more Lead-free ceramics (1 À x)(K 0.48 Na 0.52)NbO 3-(x/5.15)K 2.9 Li 1.95 Nb 5.15 O 15.3 (x = 0.3-0.6, KNN-KLN100x) were prepared by conventional sintering technique at a low temperature of 960 8C. The effects of KLN contents on microstructure, dielectric, and piezoelectric properties were investigated. After the addition of KLN, the sintering performance and Curie temperature of the ceramics were markedly improved. The ceramics with x = 0.3 exhibited very good piezoelectric properties: d 33 = 138 pC/N, k p = 45.03%, T c = 495 8C, the dielectric constant at room temperature e r (RT) = 478 and the maximum dielectric constant e r (max) = 5067. These results indicated that the KNN-KLN100x lead-free ceramics sintered at low temperatures are promising for high temperature piezoelectric applications.
Temperature dependent X-ray diffraction (XRD) and dielectric properties of perovskite Ba(Zr[Formu... more Temperature dependent X-ray diffraction (XRD) and dielectric properties of perovskite Ba(Zr[Formula: see text]Ti[Formula: see text]O3ceramic prepared using a standard solid-state reaction process is presented. Along with phase transitions at low temperature, a new phase transition at high temperature (873[Formula: see text]C at 20[Formula: see text]Hz), diffusive in character has been found where the lattice structure changes from monoclinic (space group: [Formula: see text] to hexagonal (space group: [Formula: see text]). This result places present ceramic in the list of potential candidate for intended high temperature applications. The AC conductivity data followed hopping type charge conduction and supports jump relaxation model. The experimental value of [Formula: see text][Formula: see text]pC/N was found. The dependence of polarization and strain on electric field at room temperature suggested that lead-free Ba(Zr[Formula: see text]Ti[Formula: see text]O3is a promising materi...
Lead-free Ba(In0.5Nb0.5)1-xTixO3 (0 ? x ? 1) ceramics was synthesized using a standard high tempe... more Lead-free Ba(In0.5Nb0.5)1-xTixO3 (0 ? x ? 1) ceramics was synthesized using a standard high temperature solidstate reaction method and sintered at 1400?C/4 h (except the pure BaTiO3 which was sintered at 1300?C/4 h). The ceramics was characterized by X-ray diffraction, scanning electron microscopy, dielectric, impedance and AC conductivity studies. The crystal structure of the compounds was found to be cubic (with the space group Pm3m) for x = 0,0.25 and 0.50 and tetragonal (P4/mmm) for x = 0.75 and 1.0. Increase in Ti-content in the ceramic samples leads to the decrease in unit cell volume while the values of real as well as imaginary parts of dielectric constant and AC conductivity increase. Complex impedance spectroscopy analysis indicated the negative temperature coefficient of resistance. AC conductivity data supported the hopping type of conduction in the system and obeyed Jonscher?s power law. The real and imaginary parts of dielectric constant and AC conductivity data fit ex...
Lead-free [Formula: see text](0.50(Ba[Formula: see text]Ca[Formula: see text]TiO3–0.50Ba(Zr[Formu... more Lead-free [Formula: see text](0.50(Ba[Formula: see text]Ca[Formula: see text]TiO3–0.50Ba(Zr[Formula: see text]Ti[Formula: see text]O[Formula: see text]-([Formula: see text]PVDF ceramic–polymer nanocomposites with [Formula: see text], 0.05, 0.10, 0.15, 0.20, 0.25 were prepared using melt-mixing technique. The distribution of nanoceramic filler particles (0.50(Ba[Formula: see text]Ca[Formula: see text]TiO3–0.50Ba(Zr[Formula: see text]Ti[Formula: see text]O[Formula: see text] in the PVDF matrix were examined using scanning electron microscope. Impedance analysis indicated the negative temperature coefficient of resistance character of all the test specimens. Filler concentration-dependent piezoelectric coefficient ([Formula: see text] data followed exponential growth types of variation. The data for ac conductivity were found to obey Jonscher’s power law. The correlated barrier hopping (CBH) model was found to explain the mechanism of charge transport occurring in the system. The low v...
In this work, lead-free Na 0.4 Bi 0.5 TiO 3-K 0.1 Bi 0.5 TiO 3 (NKBT) piezoelectric ceramics were... more In this work, lead-free Na 0.4 Bi 0.5 TiO 3-K 0.1 Bi 0.5 TiO 3 (NKBT) piezoelectric ceramics were prepared by the solid-state reaction method and their structural, ferroelectric and dielectric properties were systematically studied. NKBT sintered at 1150˚C for 4 h exhibited highly dense (96%-98% of the theoretical density) and uniform grains of size 1.1 μm. The coexistence of tetragonal (P4bm) and rhombohedral (R3c) phases due to the presence of morphotrophic phase boundary for the chosen composition has been confirmed by the Rietveld refinement studies. Enhanced ferroelectric properties such as remnant polarization (P r) and coercive field (E C) are found to be 37 μC/cm 2 and 30 kV/cm, respectively. The optimized synthesis procedure for NKBT ceramics resulted in enhanced strain (%) and converse piezoelectric coefficient (d 33 *) of 0.3 % and 554 pm/V which is attributed to smaller grain size and switching of non 180˚ domains. NKBT ceramics with such excellent piezoelectric properties can be considered as a promising candidate for actuator applications.
An eco-friendly lactobacillus sp. (microbe) assisted synthesis of titanium nanoparticles is repor... more An eco-friendly lactobacillus sp. (microbe) assisted synthesis of titanium nanoparticles is reported. The synthesis is performed at room temperature. X-ray and transmission electron microscopy analyses are performed to ascertain the formation of Ti nanoparticles. Individual nanoparticles as well as a number of aggregates almost spherical in shape having a size of 40-60 nm are found.
Extremely small amounts of La and Al doping on the A and B site of BaTiO 3 , respectively, result... more Extremely small amounts of La and Al doping on the A and B site of BaTiO 3 , respectively, resulting in a solid solution of the type Ba 1-3x La 2x Ti 1-3x Al 4x O 3 have been investigated. The compositions have been prepared by the Pechini process. The x-ray diffraction ͑XRD͒ reveals the presence of tetragonal ͑P4/mmm͒ phase. The XRD data has been analyzed using FULLPROF, a Rietveld refinement package. The compositions have been characterized by dielectric spectroscopy between room temperature and 200°C. The resulting compounds ͑0 ഛ x ഛ 0.008͒ exhibit a remarkable decrease in the Curie temperature as well as a significant enhancement of the dielectric constant.
Polycrystalline (Na 0.5 Sb 0.5)TiO 3 was prepared using a high-temperature solid-state reaction m... more Polycrystalline (Na 0.5 Sb 0.5)TiO 3 was prepared using a high-temperature solid-state reaction method. An XRD analysis indicated the formation of a single-phase monoclinic structure. Complex impedance studies revealed the presence of grain boundary effects from 300 • C onwards. Also, the dielectric relaxation in the system was found to be of a non-Debye type. The ac conductivity data were used to evaluate the density of states at the Fermi level, the minimum hopping length and activation energy of the compound. The dc electrical and thermal conductivities of grain and grain boundary have been assessed. The correlated barrier hopping model was found to successfully explain the mechanism of charge transport in (Na 0.5 Sb 0.5)TiO 3 .
In this contribution, the structural, electrical, dielectric, and microstructural properties of d... more In this contribution, the structural, electrical, dielectric, and microstructural properties of double perovskite Gd 2 NiMnO 6 doped with strontium were presented. The strontium-doped double perovskite Gd 2-x Sr x NiMnO 6 (x = 0, 0.1 & 0.3) was synthesized by using the solid-state reaction method. The X-ray diffraction and scanning electron microscopy characterization techniques were used to investigate the structural and surface morphological properties. The Rietveld refinement depicted the formation of pure phase having a P21/n monoclinic space group. A decrease in grain size and crystallite size was found with the dopant concentration increase, resulted in enhancement of dielectric constant of the material. The frequency-and temperature-dependent dielectric study revealed increase in dielectric constant and decrease in dielectric loss with the increase in dopant concentration. Apart from dielectric studies, the conductivity studies revealed decrease in conductivity with the increase in Sr doping, supporting the dielectric properties. In conclusion, the synthesized material is functional, has high dielectric constant, low dielectric losses and low conductivity, and, hence, it can be considered as a potential candidate for high k dielectric materials.
We demonstrate the potential of dopamine modified 0.5(Ba0.7Ca0.3)TiO3-0.5Ba(Zr0.2Ti0.8)O3 filler ... more We demonstrate the potential of dopamine modified 0.5(Ba0.7Ca0.3)TiO3-0.5Ba(Zr0.2Ti0.8)O3 filler incorporated polyvinylidene fluoride (PVDF) composite prepared by solution cast method as both flexible energy storage and harvesting devices. The introduction of dopamine in filler surface functionalization acts as bridging elements between filler and polymer matrix and results in a better filler dispersion and an improved dielectric loss tangent (<0.02) along with dielectric permittivity ranges from 9 to 34 which is favorable for both energy harvesting and storage. Additionally, a significantly low DC conductivity (< 10-9 ohm-1 cm-1) for all composites was achieved leading to an improved breakdown strength and charge accumulation capability. Maximum breakdown strength of 134 KV/mm and corresponding energy storage density 0.72 J/cm 3 were obtained from the filler content 10 weight%. The improved energy harvesting performance was characterized by obtaining a maximum piezoelectric charge constant (d33) = 78 pC/N, and output voltage (Vout) = 0.84 V along with maximum power density of 3.46 µW/cm 3 for the filler content of 10 wt%. Thus, the results show 0.5(Ba0.7Ca0.3)TiO3-0.5Ba(Zr0.2Ti0.8)O3/PVDF composite has the potential for energy storage and harvesting applications simultaneously that can significantly suppress the excess energy loss arises while utilizing different material.
Temperature-dependent dielectric permittivity of lead-free (Li x Na 1-x)NbO 3 for nominal x = 0.0... more Temperature-dependent dielectric permittivity of lead-free (Li x Na 1-x)NbO 3 for nominal x = 0.04-0.20, prepared by solid state reaction followed by sintering, was studied to resolve often debated issue pertaining to exactness of morphotropic phase boundary (MPB) location along with structural aspects and phase stability in the system near MPB. Interestingly, a diffuse phase transition has been observed in the dielectric permittivity peak arising from the disorder induced in A-site and structural frustration in the perovskite cell due to Li substitution. A partial phase diagram has been proposed based on temperature-dependent dielectric permittivity studies. The room temperature piezoelectric and ferroelectric properties were investigated and the ceramics with x = 0.12 showed relatively good electrical properties (d 33 = 28 pC/N, k p = 13.8%, Q m = 440, P r = 12.5 μC/cm 2 , E C = 43.2 kV/cm, T m = 340 o C). These parameter values make this material suitable for piezoelectric resonator and filter applications. Moreover, a high dielectric permittivity (εʹ r = 2703) with broad diffuse peak near transition temperature along with low dielectric loss (< 4%) in a wide temperature range (50-250 o C) found in this material may also have a potential 2 application in high-temperature multilayer capacitors in automotive and aerospace related industries.
For the last few years fast ion conducting lithium glasses are being studied due to their potenti... more For the last few years fast ion conducting lithium glasses are being studied due to their potential use in advanced electrochemical devices. A number of glass systems containing oxides, sulphides and other lithium compounds prepared by both conventional cooling and rapid quenching techniques have been reported. In this paper we review the transport properties of lithium ion conducting glasses. The special features of the ionic conduction process have been highlighted and some experimental techniques to study transport properties have been described. Some of the common observations of the properties have been discussed and finally some important problems for future development have been pointed out.
Impedance and electrical conduction studies of Ba(Pr 1/2 Nb 1/2)O 3 ceramic prepared through conv... more Impedance and electrical conduction studies of Ba(Pr 1/2 Nb 1/2)O 3 ceramic prepared through conventional ceramic fabrication technique are presented. The crystal symmetry, space group and unit cell dimensions were estimated using Rietveld analysis. X-ray diffraction analysis indicated the formation of a single-phase cubic structure with space group, P m3m. EDAX and SEM studies were carried out to study the quality and purity of compound. To find a correlation between the response of the real system and idealized model circuit composed of discrete electrical components, the model fittings were presented using impedance data. Complex impedance as well as electric modulus analyses suggested dielectric relaxation to be of non-Debye type and negative temperature coefficient of resistance character. The correlated barrier hopping model was employed to successfully explain the mechanism of charge transport in Ba(Pr 1/2 Nb 1/2)O 3. The a.c. conductivity data were used to evaluate density of states at Fermi level, minimum hopping length and apparent activation energy.
The homogeneous dispersion of carbon nanotubes (CNT) remains a hindrance in exploiting the except... more The homogeneous dispersion of carbon nanotubes (CNT) remains a hindrance in exploiting the exceptional properties associated with CNT in polymer/CNT composites. Here we present for the first time the key role of sodium salt of 6-aminohexanoic acid (Na-AHA) in assisting debundling the multiwall carbon nanotubes (MWNT) through specific interactions leading to homogeneous dispersion within polyamide6 (PA6) matrix during melt-mixing. The composite fabricated via this route exhibits low electrical percolation threshold of 0.5 wt% at room temperature, the lowest reported value in this system so far. FTIR and Raman spectroscopy reveal the existence of 'cation-p' interaction between Na-AHA and MWNT. The phenomenon of reactive coupling between amine functionality of Na-AHA and acid end group of PA6 during melt-mixing is also established.
New fluoride glasses in the system PbF2-MnF2-AI(PO3) a have been synthesised and found o to have ... more New fluoride glasses in the system PbF2-MnF2-AI(PO3) a have been synthesised and found o to have high d.c. conductivities, presumably due t6mobileF ions. A.C. electrical data (25-200 C) have been analyzed by impedance spectroscopy. A glass with the composition 85PbF2-5MnF 2-10AI(PO3) 3 yields a record value for conductivity in an anionic conducting glass, c200 = 1.1 × 10~(f~-cm)-1, nearly two orders of magnitude higher than the best values so far reported. Electrical and mechanical relaxation data have been compared in the isofrequency-inverse temperature representation. As seen previously for cation conductors, the mechanical relaxation is less exponential (broader) than the electrical relaxation. However, in the present case the most probable mechanical relaxation time is shorter than the most probable electrical relaxation time. MATERIALS INDEX-Fluoride glasses
International Journal of Green Nanotechnology: Physics and Chemistry
A low-cost, green, and highly reproducible microbe (Lactobacillus sp.)-mediated biosynthesis of G... more A low-cost, green, and highly reproducible microbe (Lactobacillus sp.)-mediated biosynthesis of Gd 2 O 3 nanoparticles is reported. X-ray and transmission electron microscopy analyses were performed to ascertain the formation of Gd 2 O 3 nanoparticles. X-ray analysis indicated that Gd 2 O 3 nanoparticles have a body-centered cubic (BCC) unit cell structure. Individual nanoparticles almost spherical in shape of 10-20 nm were found. An effort has been made to understand the possible involved mechanism for the biosynthesis of Gd 2 O 3 nanoparticles. The present procedure offers the benefit of eco-friendliness and amenability for large-scale production through scaling up.
A simple and rapid quenching apparatus has been designed and fabricated. The limit of glass forma... more A simple and rapid quenching apparatus has been designed and fabricated. The limit of glass formation in the system LiF-LiaO-Al(POa)a could be expanded by rapid quenching with this arrangement. The electrical conductivity of rapidly quenched glasses derived from complex impedance/admittance analysis are higher and the activation energy are lower compared to conventionally prepared glasses of corresponding chemical compositions. Annealing of the "as quenched" glasses causes considerable reduction in conductivity.
International Conference on Advanced Nanomaterials & Emerging Engineering Technologies, 2013
Phase pure (T'-type, sp. gpo I4/mmm), category of materials to be explored fully for their dielec... more Phase pure (T'-type, sp. gpo I4/mmm), category of materials to be explored fully for their dielectric nanocrystalline Gd2Cu04 powders were synthesized by a wet properties. However, the observed high £/ was contested to be chemical citrate gel complexation process known as "Pechini process". The T'-type phase was realized at much lower (_ 1073 mostly intrinsic in nature and extrinsic factors affecting £/ K) temperature than those reported for conventional ceramic were not studied. Further, these few select compounds studied powder mixing and solid state reaction process (_ 1223 K). The so far were synthesized using standard ceramic powder average particle size of the solid state reacted particles from HR-mixing and solid state reaction process, which requires high TEM was found to be-50 nm. The dielectric studies on the synthesis temperatures and often encountered with Gd2Cu04 pellets revealed extremely high values of E/ (�10 4) inhomogeneity of constituent ions. In contrast, wet chemical over the measure frequencies (1 <5. f <5. 1 MHz) and temperature synthesis process facilitates the molecular level mixing of (173 K <5. T<5. 423 K) ranges. Being non-ferroelectric, we propose constituent elements, which in turn contribute towards such high values of E/ arise due to an Internal barrier layer maintaining better stoichiometry and lower synthesis capacitance effect, formed by insulating grain boundaries and semiconducting grains in the ceramics. temperatures [7]. However, there have been a very few reports Keywords-Pechni process, T'-cuprate, giant dielectric on wet chemical synthesis of T'-type cuprates, including constant. GdzCu04 [8]. Hence, alternate method of synthesis of T'-type cuprate, viz. wet chemical process seems an interesting
Uploads
Papers by ajit kulkarni