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
A series of compounds Ba5-xSrxGdTi3V7O30 (x = 0 - 5), belonging to tungsten bronze family were prepared by a high-temperature solid-state reaction route. Using X-Ray diffraction technique and Scanning Electron Microgr...A series of compounds Ba5-xSrxGdTi3V7O30 (x = 0 - 5), belonging to tungsten bronze family were prepared by a high-temperature solid-state reaction route. Using X-Ray diffraction technique and Scanning Electron Micrograph, the formation and surface morphology of the compounds were studied. The X-Ray diffraction study informs the formation of single-phase orthorhombic structures. The substitution of Sr ion with increasing concentration in the compounds as per formula resulted in a variation of the electrical properties. Study of electrical properties using impedance analyzer exhibits: 1) the presence of negative temperature coefficients of resistance (NTCR) behavior;2) presence of temperature dependent electrical relaxation phenomena;3) evidences of single electrical relaxation attributed to the presence of bulk contribution to the electrical properties for pure Ba5GdTi3V7O30 compound;4) an enhancement in the barrier to the mobility of charge carriers on Sr-substitution. The effects of Sr on changes in the electrical conductivity as a function of temperature at different frequency are described based on impedance spectrum analysis.展开更多
This research article reports electrical characterization of a rare earth molybdate based on combination of rare earth (La+3) and alkali (Li+) metal ions. The experimental observation suggests the negative temperature...This research article reports electrical characterization of a rare earth molybdate based on combination of rare earth (La+3) and alkali (Li+) metal ions. The experimental observation suggests the negative temperature coefficient of resistance behavior of the material. The material has been prepared by standard solid state reaction method, where the synthesis conditions have been optimized by thermal analysis. A possible mechanism for the formation of the polycrystal-line LaLiMo2O8 is reported. A systematic analysis has been done to determine the crystal structure of the powder material and it was found that the powder material was crystallized to tetragonal unit cell structure. Electrical properties have been studied using a.c. impedance measurement. The temperature variation of electrical conductivity of the material shows typical Arrhenius behavior. The activation energy evaluated from conductivity data works out to be ~0.94 ev.展开更多
The polycrystalline sample of Ba5GdTi3V7O30 , a member of tungsten bronze structural family, was prepared by a high-temperature solid-state reaction technique. A preliminary X-ray diffraction analysis suggests the for...The polycrystalline sample of Ba5GdTi3V7O30 , a member of tungsten bronze structural family, was prepared by a high-temperature solid-state reaction technique. A preliminary X-ray diffraction analysis suggests the formation of single-phase compound with orthorhombic structure. The effect of temperature on impedance parameters was studied using an impedance analyzer in a wide frequency range (102- 106 Hz) at different temperatures. The real and imaginary part of complex impedance traces semicircle(s) in the complex plane. The temperature dependent plots reveal the presence of both bulk and grain boundary effects. The bulk resistance of the material decreases with rise in temperature. This exhibits a typical negative temperature coefficient of resistance (NTCR) behavior of the material. The modulus analysis suggests a possible hopping mechanism for electrical transport processes of the material. The nature of variation of dc conductivity suggests Arrhenius type of electrical conductivity.展开更多
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A series of compounds Ba5-xSrxGdTi3V7O30 (x = 0 - 5), belonging to tungsten bronze family were prepared by a high-temperature solid-state reaction route. Using X-Ray diffraction technique and Scanning Electron Micrograph, the formation and surface morphology of the compounds were studied. The X-Ray diffraction study informs the formation of single-phase orthorhombic structures. The substitution of Sr ion with increasing concentration in the compounds as per formula resulted in a variation of the electrical properties. Study of electrical properties using impedance analyzer exhibits: 1) the presence of negative temperature coefficients of resistance (NTCR) behavior;2) presence of temperature dependent electrical relaxation phenomena;3) evidences of single electrical relaxation attributed to the presence of bulk contribution to the electrical properties for pure Ba5GdTi3V7O30 compound;4) an enhancement in the barrier to the mobility of charge carriers on Sr-substitution. The effects of Sr on changes in the electrical conductivity as a function of temperature at different frequency are described based on impedance spectrum analysis.
文摘This research article reports electrical characterization of a rare earth molybdate based on combination of rare earth (La+3) and alkali (Li+) metal ions. The experimental observation suggests the negative temperature coefficient of resistance behavior of the material. The material has been prepared by standard solid state reaction method, where the synthesis conditions have been optimized by thermal analysis. A possible mechanism for the formation of the polycrystal-line LaLiMo2O8 is reported. A systematic analysis has been done to determine the crystal structure of the powder material and it was found that the powder material was crystallized to tetragonal unit cell structure. Electrical properties have been studied using a.c. impedance measurement. The temperature variation of electrical conductivity of the material shows typical Arrhenius behavior. The activation energy evaluated from conductivity data works out to be ~0.94 ev.
文摘The polycrystalline sample of Ba5GdTi3V7O30 , a member of tungsten bronze structural family, was prepared by a high-temperature solid-state reaction technique. A preliminary X-ray diffraction analysis suggests the formation of single-phase compound with orthorhombic structure. The effect of temperature on impedance parameters was studied using an impedance analyzer in a wide frequency range (102- 106 Hz) at different temperatures. The real and imaginary part of complex impedance traces semicircle(s) in the complex plane. The temperature dependent plots reveal the presence of both bulk and grain boundary effects. The bulk resistance of the material decreases with rise in temperature. This exhibits a typical negative temperature coefficient of resistance (NTCR) behavior of the material. The modulus analysis suggests a possible hopping mechanism for electrical transport processes of the material. The nature of variation of dc conductivity suggests Arrhenius type of electrical conductivity.
