The complex perovskite oxide a strontium gadolinium niobate (SGN) synthesized by solid-state reaction technique has single phase with tetragonal structure. X-ray diffraction (XRD) technique and scanning electron micro...The complex perovskite oxide a strontium gadolinium niobate (SGN) synthesized by solid-state reaction technique has single phase with tetragonal structure. X-ray diffraction (XRD) technique and scanning electron microscopy (SEM) were used to study the structural and microstructural properties of the ceramics, respectively. The XRD patterns of SGN at room temperature show a tetragonal structure. Studies of the dielectric constant and dielectric loss of compound as a function of frequency (50 Hz to 1 MHz) at room temperature, and as a function of temperature (60°C to 420°C) indicate polydispersive nature of the material. The logarithmic angular frequency dependence of the loss peak is found to obey the Arrhenius law with activation energy ~0.18 eV. The small value of activation energy of the compound (~0.18 eV) can be explained by mixed ionic-polaronic conductivity mechanism. The grain size of the pellet sample was found to be 1.92 μm. The frequency-dependant electrical data are analyzed in the framework of conductivity and electric modulus formalisms. The complex plane impedance plot shows the grain boundary contribution for higher value of dielectric constant in the law frequency region.展开更多
A complex structure of barium iron niobate, Ba(Fe0.5Nb0.5)O3 (BFN) and strontium titanate SrTiO3 (ST) was fabricated by a solid-state reaction method. The phase formation of Ba(Fe0.5Nb0.5)O3-SrTiO3 was checked using X...A complex structure of barium iron niobate, Ba(Fe0.5Nb0.5)O3 (BFN) and strontium titanate SrTiO3 (ST) was fabricated by a solid-state reaction method. The phase formation of Ba(Fe0.5Nb0.5)O3-SrTiO3 was checked using X-ray diffraction (XRD) technique. The X-ray structural analysis of BFN and BFN-ST ceramics, showed the formation of single-phase compound in the monoclinic system, which is a distorted structure of an ideal cubic perovskite. Careful examination of microstructures of the individual compounds of the system was done by the scanning electron micrograph (SEM), and confirms the polycrystalline nature of the systems. Detailed studies of dielectric and electrical impedance properties of the systems in a wide range of frequency (100Hz - 5MHz) and different temperatures (30°C-285°C) showed that these properties are strongly dependent on temperature and frequency.展开更多
Polycrystalline samples of samarium barium tungstate[Sm_(2)(Ba_(0.5)W_(0.5)T_(2)O_(7):(SBW)]pyrochlore structure type oxides have been prepared by a solid-state reaction technique.X-ray di®raction(XRD)patterns of...Polycrystalline samples of samarium barium tungstate[Sm_(2)(Ba_(0.5)W_(0.5)T_(2)O_(7):(SBW)]pyrochlore structure type oxides have been prepared by a solid-state reaction technique.X-ray di®raction(XRD)patterns of this compound at room temperature suggest the formation of a single phase compound with orthorhombic structure.Studies of the dielectric constant and dielectric loss of compound as a function of frequency(4 kHz-1MHz)at room temperature,and as a function of temperature(23-350℃)at 20 and 50 kHz frequencies suggest that the compound does not have dielectric anomaly.The variation of dc resistivity suggests the semiconductor characteristics of the material.The value of activation energy(E_(a)-0.43 at 20 kHz and E_(a)-0.29 at 50 kHz)of the above mentioned compound has been calculated from the slope of the ln-ac versus 1/T graph in the high temperature region(>240℃).The low value of activation energy supports the superionic nature of the compounds in the high temperature region.展开更多
文摘The complex perovskite oxide a strontium gadolinium niobate (SGN) synthesized by solid-state reaction technique has single phase with tetragonal structure. X-ray diffraction (XRD) technique and scanning electron microscopy (SEM) were used to study the structural and microstructural properties of the ceramics, respectively. The XRD patterns of SGN at room temperature show a tetragonal structure. Studies of the dielectric constant and dielectric loss of compound as a function of frequency (50 Hz to 1 MHz) at room temperature, and as a function of temperature (60°C to 420°C) indicate polydispersive nature of the material. The logarithmic angular frequency dependence of the loss peak is found to obey the Arrhenius law with activation energy ~0.18 eV. The small value of activation energy of the compound (~0.18 eV) can be explained by mixed ionic-polaronic conductivity mechanism. The grain size of the pellet sample was found to be 1.92 μm. The frequency-dependant electrical data are analyzed in the framework of conductivity and electric modulus formalisms. The complex plane impedance plot shows the grain boundary contribution for higher value of dielectric constant in the law frequency region.
文摘A complex structure of barium iron niobate, Ba(Fe0.5Nb0.5)O3 (BFN) and strontium titanate SrTiO3 (ST) was fabricated by a solid-state reaction method. The phase formation of Ba(Fe0.5Nb0.5)O3-SrTiO3 was checked using X-ray diffraction (XRD) technique. The X-ray structural analysis of BFN and BFN-ST ceramics, showed the formation of single-phase compound in the monoclinic system, which is a distorted structure of an ideal cubic perovskite. Careful examination of microstructures of the individual compounds of the system was done by the scanning electron micrograph (SEM), and confirms the polycrystalline nature of the systems. Detailed studies of dielectric and electrical impedance properties of the systems in a wide range of frequency (100Hz - 5MHz) and different temperatures (30°C-285°C) showed that these properties are strongly dependent on temperature and frequency.
文摘Polycrystalline samples of samarium barium tungstate[Sm_(2)(Ba_(0.5)W_(0.5)T_(2)O_(7):(SBW)]pyrochlore structure type oxides have been prepared by a solid-state reaction technique.X-ray di®raction(XRD)patterns of this compound at room temperature suggest the formation of a single phase compound with orthorhombic structure.Studies of the dielectric constant and dielectric loss of compound as a function of frequency(4 kHz-1MHz)at room temperature,and as a function of temperature(23-350℃)at 20 and 50 kHz frequencies suggest that the compound does not have dielectric anomaly.The variation of dc resistivity suggests the semiconductor characteristics of the material.The value of activation energy(E_(a)-0.43 at 20 kHz and E_(a)-0.29 at 50 kHz)of the above mentioned compound has been calculated from the slope of the ln-ac versus 1/T graph in the high temperature region(>240℃).The low value of activation energy supports the superionic nature of the compounds in the high temperature region.
