The polycrystalline samples of complex tungsten bronze(TB)Na_(2)Pb_(2)R_(2)W_(2)Ti_(4)V_(4)O_(30)(R=Dy,Pr)compounds were prepared by solid-state reaction technique.Room-temperature preliminary structural studies confi...The polycrystalline samples of complex tungsten bronze(TB)Na_(2)Pb_(2)R_(2)W_(2)Ti_(4)V_(4)O_(30)(R=Dy,Pr)compounds were prepared by solid-state reaction technique.Room-temperature preliminary structural studies confirm the formation of the compounds in the orthorhombic crystal system.Detailed studies of electrical properties of the materials using complex impedance spectroscopy technique exhibit that the impedance and related parameters are strongly dependent upon temperature and microstructure(bulk,grain boundary,etc).An observation of negative temperature coefficient of resistance(NTCR)suggests the materials have semiconducting properties.The variation of AC conductivity with temperature shows a typical Arrhenius behavior of the materials.Both the samples obey Jonscher’s universal power law.The existence of hopping mechanism in the electrical transport processes in the system with non-exponential type of conductivity relaxation is confirmed by electrical modulus analysis.展开更多
The polycrystalline ceramic Pb0.5Ba1.5BiVO6 manifesting the complex double perovskite structure was tailored by the conventional solid state route at a moderate temperature.Qualitative phase analysis and formation of ...The polycrystalline ceramic Pb0.5Ba1.5BiVO6 manifesting the complex double perovskite structure was tailored by the conventional solid state route at a moderate temperature.Qualitative phase analysis and formation of the ceramic were affirmed by XRD analysis.The X-ray powder diffraction pattern of the compound explored at room temperature affirms the single phase formation with double perovskite structure exhibiting rhombohedral phase.Microstructural analysis of the studied compound procured from the Scanning Electron Microscope(SEM)validates the formation of dense microstructures and nonuniformly distributed grains with minimal voids.Compositional analysis was shaped through the Electron Diffraction Spectroscopy(EDS)confirming the absence of con-tamination of any other metals apart from the mentioned ones.Dielectric(Cr and tanδ)parameters of the compound were studied using the LCR analyzer at different temperatures and wide range of frequencies.The polarization and dielectric study affirms the presence of ferroelectricity in the material with transition temperature much above the room temperature.The tangent dielectric loss of this sample being almost minimal at room temperature attributes it to find applications in different grounds of electronics.Optical equities of the ceramic were further analyzed by the RAMAN,FTIR,UV–Vis and Photoluminescence spectroscopy.展开更多
The polycrystalline sample of Li_(2)Pb_(2)Pr_(2)W_(2)Ti_(4)V_(4)O_(30) was prepared by a solid-state reaction technique.The preparation conditions of the compound have been optimized using thermal analysis(DTA and TGA...The polycrystalline sample of Li_(2)Pb_(2)Pr_(2)W_(2)Ti_(4)V_(4)O_(30) was prepared by a solid-state reaction technique.The preparation conditions of the compound have been optimized using thermal analysis(DTA and TGA)technique.Room temperature structural analysis confirms the formation of single phase compound in orthorhombic crystal system.The surface morphology of the sample,recorded by scanning electron microscope,shows uniform grain distribution on the surface of the sample.The observation of hysteresis loop confirmed that the material has ferroelectric properties at room temperature.Electrical properties of the material were studied by complex impedance spectroscopic technique.Temperature dependence of electrical parameters(impedance,modulus,etc.)is strongly correlated to the micro-structural characteristics(bulk,grain boundary,etc.)of the sample.A typical temperature-dependent resistive characteristic of the sample(i.e.,negative temperature coe±cient of resistance(NTCR))exhibits its semiconducting properties.The temperature dependence of dc conductivity shows a typical Arrhenius behavior.A signature of ionic conductivity in the system was observed in ac conductivity spectrum.The sample obeys Jonscher's universal power law.The hopping mechanism for electrical transport properties of the system with nonexponential-type conductivity relaxation was suggested from the electrical modulus analysis.展开更多
文摘The polycrystalline samples of complex tungsten bronze(TB)Na_(2)Pb_(2)R_(2)W_(2)Ti_(4)V_(4)O_(30)(R=Dy,Pr)compounds were prepared by solid-state reaction technique.Room-temperature preliminary structural studies confirm the formation of the compounds in the orthorhombic crystal system.Detailed studies of electrical properties of the materials using complex impedance spectroscopy technique exhibit that the impedance and related parameters are strongly dependent upon temperature and microstructure(bulk,grain boundary,etc).An observation of negative temperature coefficient of resistance(NTCR)suggests the materials have semiconducting properties.The variation of AC conductivity with temperature shows a typical Arrhenius behavior of the materials.Both the samples obey Jonscher’s universal power law.The existence of hopping mechanism in the electrical transport processes in the system with non-exponential type of conductivity relaxation is confirmed by electrical modulus analysis.
文摘The polycrystalline ceramic Pb0.5Ba1.5BiVO6 manifesting the complex double perovskite structure was tailored by the conventional solid state route at a moderate temperature.Qualitative phase analysis and formation of the ceramic were affirmed by XRD analysis.The X-ray powder diffraction pattern of the compound explored at room temperature affirms the single phase formation with double perovskite structure exhibiting rhombohedral phase.Microstructural analysis of the studied compound procured from the Scanning Electron Microscope(SEM)validates the formation of dense microstructures and nonuniformly distributed grains with minimal voids.Compositional analysis was shaped through the Electron Diffraction Spectroscopy(EDS)confirming the absence of con-tamination of any other metals apart from the mentioned ones.Dielectric(Cr and tanδ)parameters of the compound were studied using the LCR analyzer at different temperatures and wide range of frequencies.The polarization and dielectric study affirms the presence of ferroelectricity in the material with transition temperature much above the room temperature.The tangent dielectric loss of this sample being almost minimal at room temperature attributes it to find applications in different grounds of electronics.Optical equities of the ceramic were further analyzed by the RAMAN,FTIR,UV–Vis and Photoluminescence spectroscopy.
文摘The polycrystalline sample of Li_(2)Pb_(2)Pr_(2)W_(2)Ti_(4)V_(4)O_(30) was prepared by a solid-state reaction technique.The preparation conditions of the compound have been optimized using thermal analysis(DTA and TGA)technique.Room temperature structural analysis confirms the formation of single phase compound in orthorhombic crystal system.The surface morphology of the sample,recorded by scanning electron microscope,shows uniform grain distribution on the surface of the sample.The observation of hysteresis loop confirmed that the material has ferroelectric properties at room temperature.Electrical properties of the material were studied by complex impedance spectroscopic technique.Temperature dependence of electrical parameters(impedance,modulus,etc.)is strongly correlated to the micro-structural characteristics(bulk,grain boundary,etc.)of the sample.A typical temperature-dependent resistive characteristic of the sample(i.e.,negative temperature coe±cient of resistance(NTCR))exhibits its semiconducting properties.The temperature dependence of dc conductivity shows a typical Arrhenius behavior.A signature of ionic conductivity in the system was observed in ac conductivity spectrum.The sample obeys Jonscher's universal power law.The hopping mechanism for electrical transport properties of the system with nonexponential-type conductivity relaxation was suggested from the electrical modulus analysis.
