Structural and impedance properties of KBa2V5O15 ceramics

The polycrystalline sample of KBa{sub 2}V{sub 5}O{sub 15} ceramics was prepared by a mixed oxide method at low temperature (i.e., at 560 deg. C). The formation of the compound was confirmed using an X-ray diffraction technique at room temperature. Scanning electron micrograph of the material showed uniform grain distribution on the surface of the sample. Detailed studies of dielectric properties of the compound as a function of temperature at different frequencies suggest that the compound has a dielectric anomaly of ferroelectric to paraelectric type at 323 deg. C, and exhibits diffuse phase transition. Electrical properties of the material were analyzed using a complex impedance technique. The Nyquists plot showed the presence of both grain (>10{sup 3} Hz) and the grain boundary (<10{sup 3} Hz) effects in the material. Studies of electrical conductivity over a wide temperature range suggest that the compound exhibits the negative temperature coefficient of resistance behavior. The ac conductivity spectrum was found to obey Jonscher's universal power law.