Study of Structural and Electrical Properties of a New Type of Complex Tungsten Bronze Electroceramics; Li2Pb2Y2W2Ti4V4O30

Abstract

A polycrystalline ceramic, a new type of complex tungsten bronze type structure, having a general formula Li2Pb2Y2W2Ti4V4O30 has been prepared relatively at low temperature using a mixedoxide technique after optimizing the calcination conditions on the basis of thermal analysis. The material has been characterized by different experimental techniques. The formation of the material under the reported conditions has been confirmed by an X-ray diffraction technique. A preliminary structural analysis of the material showed the formation of single phase compound in an orthorhombic crystal structure at room temperature. Studies of dielectric properties (εr, tanδ ) of the above compound as a function of temperature at different frequencies exhibit a ferroelectric phase transition of diffuse type. The electrical properties of the material have been studied using ac impedance spectroscopy technique. Detailed studies of impedance and related parameters exhibit that the electrical properties of the material are strongly dependent on temperature, and bear a good correlation with its microstructure. The temperature dependence of electrical relaxation phenomenon in the material has been observed. The bulk resistance, evaluated from complex impedance spectra, is found to decrease with rise in temperature, exhibiting a typical negative temperature co-efficient of resistance (NTCR) – type behavior similar to that of semiconductors. A small contribution of grain boundary effect was also observed. The complex electric modulus analysis indicates the possibility of hopping conduction mechanism in the system with non-exponential type of conductivity relaxation. The ac conductivity spectra exhibit a typical signature of an ionic conducting system, and are found to obey Jonscher’s universal power law.