Pakistan Journal of Scientific & Industrial Research Series A: Physical Sciences
Glass samples of compositions xV2O5 +y Pb+ [100-(x+y)] B2O3 with the number of moles x varying fr... more Glass samples of compositions xV2O5 +y Pb+ [100-(x+y)] B2O3 with the number of moles x varying from 0 to 2.5% and y varying from 0.2 to 0.195% are prepared by the technique of melting and quenching. The structural analysis of glass is achieved by studying the density and the molar volume. The glass density is increased from 1.8748 to 1.9347 g/cm according to the increase of the vanadium pentoxide contents. Also, the structural analysis of these glasses points out the conversion of structural units of BO3 into BO4, which leads to increased density and molar volume. However, the transition temperature, the crystallization temperature, and the glass stability are decreased. The VO4 and VO5 structural units of vanadium are formed in the structural network. The electronic conduction of borate glass can be explained using Polaron hopping between V +4 and V +5. On the other hand, ionic conduction takes place by the Pb ion movement in all of the studied samples.
A glass system according to the molar formula (70% mole V2O5- (15-x)% mole P2O5-15% mole B2O3), w... more A glass system according to the molar formula (70% mole V2O5- (15-x)% mole P2O5-15% mole B2O3), where x = 0, 1, 2.5, 5 and 7.5 % mole Fe2O3, was prepared by melting the pure powder chemicals at porcelain crucibles at 1000Co for three hours until the homogenous glass was obtained. The samples were quenched in air and heat-treated at 500 Co for 1, 2 and 3 h. The density, the molar volume, the electrical conductivity and magnetic properties were measured before and after the heat-treatment. The crystalline phases due to heat-treatment were determined using x-ray diffraction. The heat-treatment causes change of BO3 to BO4 and forming non-bridging oxygen. Replacing the phosphorus oxide with the iron oxide increases the magnetic properties while the conductivity increase up to 5% mole and then decreases. The changes of electrical and magnetic properties with heat-treatment time have a random behavior due to the change of the structure if the samples with heat treatment.
A series of samples of Co 1Àx Cd x Fe 2 O 4 (x ¼ 0; 0.1, 0.3, 0.5, 0.7and 0.9) were prepared by t... more A series of samples of Co 1Àx Cd x Fe 2 O 4 (x ¼ 0; 0.1, 0.3, 0.5, 0.7and 0.9) were prepared by the usual ceramic technique and sintered at 1473 K for 6 h. The X-ray analysis shows the existence of single phase spinel structure with the increase of lattice parameter and density with increasing Cd contents whereas the porosity decreases. The DC electrical conductivity increases with increasing temperature. It is also increased by increasing Cd content and reaches maximum at x ¼ 0:7 at which the activation energy for conduction becomes minimum. The transition temperature T c shifts to a higher value as Cd content increases. The thermoelectric power a is converted from a positive value for Co ferrite (hole) to a negative value for the mixed ferrite Co 1Àx Cd x Fe 2 O 4 : The activation energy for mobility E m is nearly equal to E s and the thermoelectric power a is nearly constant with the variation of temperature which make together a strong reason for the presence of hopping condition mechanism.
A glass system according to the molar formula (60% P 2 O 5-(35-Z) % PbO-5%Fe 2 O 3-Z PbX 2) where... more A glass system according to the molar formula (60% P 2 O 5-(35-Z) % PbO-5%Fe 2 O 3-Z PbX 2) where (Z= 0, 5 and (X= Fl, Cl and Br) was prepared. The density, molar volume, electrical conductivity, magnetic Susceptibility and DTA for the glass system were measured and discussed. The density, glass transition temperature and glass stability were decreased while the molar volume, electrical conductivity, magnetic susceptibility were increased when the halide ions replaced the oxygen ions in the glass matrix. The variations of the measured properties were explained as a function of the halide ions behavior in the glass system.
X-ray diffraction and infrared measurements were performed on vanadium borophosphate glass contai... more X-ray diffraction and infrared measurements were performed on vanadium borophosphate glass containing different amounts of iron ranging from 0-7.5 mol % and heat treated at 300 ~ for various times. The structure and phase separation could be determined for each glass composition. V205 was the main precipitated phase in all heat-treated samples, and its amount was dependent on the heat-treatment time and Fe203 content. Also FeP was detected in samples heat treated for 24 h. The infrared measurements showed the presence of both V 4+ and V ~+. The symmetry of V20 4-and VO]-groups was found to increase with increasing Fe203 content. It was also found that some P04 changed to BO3, forming a non-bridging oxygen.
... and AG Mostafa, J. Mater. Sci. Lett., 4 (1980) 309. 19 MK EI-Mously, M. E Kotkata and SA Sala... more ... and AG Mostafa, J. Mater. Sci. Lett., 4 (1980) 309. 19 MK EI-Mously, M. E Kotkata and SA Salah, J. Phys. C 11 (1978) 1077. 20 AM Sanad, I. Kashif, AM Abou A1-Azm, MA Khaled and H. Farouk, J. Mater. Sci., 21 (1986) 230. 21 1. Kashif, H. Farouk, SA Aly, EE Assem and AM ...
ABSTRACT Two glass samples were prepared according to the molar formula (20%X–40%B2O3–40%SiO2), w... more ABSTRACT Two glass samples were prepared according to the molar formula (20%X–40%B2O3–40%SiO2), where X = CaO or CaF2. The glass was melted at 1300°C for 3 h until homogenous glass was obtained. The glass samples were heat-treated at 700°C for 2 h and at 850°C for different times. The green glass obtained has low dielectric constant and positive magnetic susceptibility. The molar volume, scanning electron microscope and differential thermal analysis studies showed that the crystallization rate increases with an increase in the sintering time. The replacement of CaO by CaF2 improves the physical properties of the glass. The existence of fluorine ions increases the electrical conductivity, magnetic susceptibility, molar volume, dielectric constant and effective overall reaction rate (κ). All measured properties have a random behaviour with sintering time due to phase separation and asymmetry of crystallization.
Journal of Materials Science: Materials in Electronics, 1992
The effect of the addition of Fe203 and heat treatment duration on the magnetic susceptibility of... more The effect of the addition of Fe203 and heat treatment duration on the magnetic susceptibility of vanadium borophosphate glass were studied. The magnetic susceptibility of glass samples was found to increase with increasing Fe203 content, which may be explained by the formation of the Fe08 group and the change of Fe 2+ to Fe 3+ which has higher paramagnetic properties. No detectable changes in the magnetic susceptibility with heat treatment for the samples containing 0.0, 0.5 and 1.0 mol % Fe203 was observed. The magnetic susceptibility for the heat treated samples containing 2.5, 5.0 and 7.5 mol % Fe203 decreases sharply with increasing duration of heat treatment up to 6h and then remains almost constant. The sharp decrease in magnetic susceptibility of 2.5 mol % Fe20z is attributed to the increase in the number of ferrous ions. The sharp decrease for samples containing 5.0 and 7.5 mol% Fe203 is attributed to the increase in the number of Fe 3÷ in tetrahedral coordination. The rate of crystallization owing to the heat treatment was calculated and was found to increase with increasing iron oxide content. The geometry of crystallization was found to be in three-, twoand one-dimension(s) for samples containing 2.5, 5.0 and 7.5 mol % Fe203, respectively.
Journal of Materials Science: Materials in Electronics, 1992
... MA KHALED, SA ALY and H. FAROUK, J. Phys. Chem. Glasses 30 (1988) 1. 7. Y. MEOLLER, "Ino... more ... MA KHALED, SA ALY and H. FAROUK, J. Phys. Chem. Glasses 30 (1988) 1. 7. Y. MEOLLER, "Inorganic chemistry" (Asia Publishing Houses, New York, 1968). 8. O. GROWSKI, L. HURAUSKI, W. LIZAK, H. BIN-CZYCKA and J. SAWICKI, J. Physique 14 (1981) 177. 9. I. SAWAI, ...
Pakistan Journal of Scientific & Industrial Research Series A: Physical Sciences
Glass samples of compositions xV2O5 +y Pb+ [100-(x+y)] B2O3 with the number of moles x varying fr... more Glass samples of compositions xV2O5 +y Pb+ [100-(x+y)] B2O3 with the number of moles x varying from 0 to 2.5% and y varying from 0.2 to 0.195% are prepared by the technique of melting and quenching. The structural analysis of glass is achieved by studying the density and the molar volume. The glass density is increased from 1.8748 to 1.9347 g/cm according to the increase of the vanadium pentoxide contents. Also, the structural analysis of these glasses points out the conversion of structural units of BO3 into BO4, which leads to increased density and molar volume. However, the transition temperature, the crystallization temperature, and the glass stability are decreased. The VO4 and VO5 structural units of vanadium are formed in the structural network. The electronic conduction of borate glass can be explained using Polaron hopping between V +4 and V +5. On the other hand, ionic conduction takes place by the Pb ion movement in all of the studied samples.
A glass system according to the molar formula (70% mole V2O5- (15-x)% mole P2O5-15% mole B2O3), w... more A glass system according to the molar formula (70% mole V2O5- (15-x)% mole P2O5-15% mole B2O3), where x = 0, 1, 2.5, 5 and 7.5 % mole Fe2O3, was prepared by melting the pure powder chemicals at porcelain crucibles at 1000Co for three hours until the homogenous glass was obtained. The samples were quenched in air and heat-treated at 500 Co for 1, 2 and 3 h. The density, the molar volume, the electrical conductivity and magnetic properties were measured before and after the heat-treatment. The crystalline phases due to heat-treatment were determined using x-ray diffraction. The heat-treatment causes change of BO3 to BO4 and forming non-bridging oxygen. Replacing the phosphorus oxide with the iron oxide increases the magnetic properties while the conductivity increase up to 5% mole and then decreases. The changes of electrical and magnetic properties with heat-treatment time have a random behavior due to the change of the structure if the samples with heat treatment.
A series of samples of Co 1Àx Cd x Fe 2 O 4 (x ¼ 0; 0.1, 0.3, 0.5, 0.7and 0.9) were prepared by t... more A series of samples of Co 1Àx Cd x Fe 2 O 4 (x ¼ 0; 0.1, 0.3, 0.5, 0.7and 0.9) were prepared by the usual ceramic technique and sintered at 1473 K for 6 h. The X-ray analysis shows the existence of single phase spinel structure with the increase of lattice parameter and density with increasing Cd contents whereas the porosity decreases. The DC electrical conductivity increases with increasing temperature. It is also increased by increasing Cd content and reaches maximum at x ¼ 0:7 at which the activation energy for conduction becomes minimum. The transition temperature T c shifts to a higher value as Cd content increases. The thermoelectric power a is converted from a positive value for Co ferrite (hole) to a negative value for the mixed ferrite Co 1Àx Cd x Fe 2 O 4 : The activation energy for mobility E m is nearly equal to E s and the thermoelectric power a is nearly constant with the variation of temperature which make together a strong reason for the presence of hopping condition mechanism.
A glass system according to the molar formula (60% P 2 O 5-(35-Z) % PbO-5%Fe 2 O 3-Z PbX 2) where... more A glass system according to the molar formula (60% P 2 O 5-(35-Z) % PbO-5%Fe 2 O 3-Z PbX 2) where (Z= 0, 5 and (X= Fl, Cl and Br) was prepared. The density, molar volume, electrical conductivity, magnetic Susceptibility and DTA for the glass system were measured and discussed. The density, glass transition temperature and glass stability were decreased while the molar volume, electrical conductivity, magnetic susceptibility were increased when the halide ions replaced the oxygen ions in the glass matrix. The variations of the measured properties were explained as a function of the halide ions behavior in the glass system.
X-ray diffraction and infrared measurements were performed on vanadium borophosphate glass contai... more X-ray diffraction and infrared measurements were performed on vanadium borophosphate glass containing different amounts of iron ranging from 0-7.5 mol % and heat treated at 300 ~ for various times. The structure and phase separation could be determined for each glass composition. V205 was the main precipitated phase in all heat-treated samples, and its amount was dependent on the heat-treatment time and Fe203 content. Also FeP was detected in samples heat treated for 24 h. The infrared measurements showed the presence of both V 4+ and V ~+. The symmetry of V20 4-and VO]-groups was found to increase with increasing Fe203 content. It was also found that some P04 changed to BO3, forming a non-bridging oxygen.
... and AG Mostafa, J. Mater. Sci. Lett., 4 (1980) 309. 19 MK EI-Mously, M. E Kotkata and SA Sala... more ... and AG Mostafa, J. Mater. Sci. Lett., 4 (1980) 309. 19 MK EI-Mously, M. E Kotkata and SA Salah, J. Phys. C 11 (1978) 1077. 20 AM Sanad, I. Kashif, AM Abou A1-Azm, MA Khaled and H. Farouk, J. Mater. Sci., 21 (1986) 230. 21 1. Kashif, H. Farouk, SA Aly, EE Assem and AM ...
ABSTRACT Two glass samples were prepared according to the molar formula (20%X–40%B2O3–40%SiO2), w... more ABSTRACT Two glass samples were prepared according to the molar formula (20%X–40%B2O3–40%SiO2), where X = CaO or CaF2. The glass was melted at 1300°C for 3 h until homogenous glass was obtained. The glass samples were heat-treated at 700°C for 2 h and at 850°C for different times. The green glass obtained has low dielectric constant and positive magnetic susceptibility. The molar volume, scanning electron microscope and differential thermal analysis studies showed that the crystallization rate increases with an increase in the sintering time. The replacement of CaO by CaF2 improves the physical properties of the glass. The existence of fluorine ions increases the electrical conductivity, magnetic susceptibility, molar volume, dielectric constant and effective overall reaction rate (κ). All measured properties have a random behaviour with sintering time due to phase separation and asymmetry of crystallization.
Journal of Materials Science: Materials in Electronics, 1992
The effect of the addition of Fe203 and heat treatment duration on the magnetic susceptibility of... more The effect of the addition of Fe203 and heat treatment duration on the magnetic susceptibility of vanadium borophosphate glass were studied. The magnetic susceptibility of glass samples was found to increase with increasing Fe203 content, which may be explained by the formation of the Fe08 group and the change of Fe 2+ to Fe 3+ which has higher paramagnetic properties. No detectable changes in the magnetic susceptibility with heat treatment for the samples containing 0.0, 0.5 and 1.0 mol % Fe203 was observed. The magnetic susceptibility for the heat treated samples containing 2.5, 5.0 and 7.5 mol % Fe203 decreases sharply with increasing duration of heat treatment up to 6h and then remains almost constant. The sharp decrease in magnetic susceptibility of 2.5 mol % Fe20z is attributed to the increase in the number of ferrous ions. The sharp decrease for samples containing 5.0 and 7.5 mol% Fe203 is attributed to the increase in the number of Fe 3÷ in tetrahedral coordination. The rate of crystallization owing to the heat treatment was calculated and was found to increase with increasing iron oxide content. The geometry of crystallization was found to be in three-, twoand one-dimension(s) for samples containing 2.5, 5.0 and 7.5 mol % Fe203, respectively.
Journal of Materials Science: Materials in Electronics, 1992
... MA KHALED, SA ALY and H. FAROUK, J. Phys. Chem. Glasses 30 (1988) 1. 7. Y. MEOLLER, "Ino... more ... MA KHALED, SA ALY and H. FAROUK, J. Phys. Chem. Glasses 30 (1988) 1. 7. Y. MEOLLER, "Inorganic chemistry" (Asia Publishing Houses, New York, 1968). 8. O. GROWSKI, L. HURAUSKI, W. LIZAK, H. BIN-CZYCKA and J. SAWICKI, J. Physique 14 (1981) 177. 9. I. SAWAI, ...
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