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.
Highlights
Since the discovery of ferroelectric properties in BaTiO3 of perovskite structural family of ABO3 type (A = monodivalent and B = tri-hexavalent ions), a large number of oxides of different structural family have been investigated in the past in search of new and promising materials for industrial applications
The thermogravimetric analysis (TGA) pattern of the mixture recorded from room temperature to 1000 ̊C
The polycrystalline sample of Li2Pb2Y2W2Ti4V4O30 was prepared by a mixed-oxide technique
Summary
Have widely been studied by different research groups [18,19,20] The TB structure (derived from perovskite ABO3 type) consists of a complex array of distorted BO6 octahedral sharing corners in such a way that three different types of interstices (A, B and C) are available for cation substitutions in a general formula (A1) (A2) (C4) (B1) (B2) O30 In this structure mono or divalent cations can be accommodated at the A-sites (A1 and A2), tri or pentavalent cations at octahedral sites (B1 and B2) [21] and C-site are generally have small ions or empty. TB-structure compound Li2Pb2Y2W2Ti4V4O30 having all the valence elements (I-VI), and studied its structural, dielectric and electrical properties as a function of temperature at different frequency
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