Poling effect on the dielectric, pyroelectric and electrical conductivity of ferroelectric ordered–disordered Ba(Ni 0.5Nb 0.5)O 3

Abstract

The investigation of ferroelectrics possessing a diffuse phase transition is of great interest because they have unique physical properties and wide practical applications. They do not show a sharp change of structural and transport properties at the Curie point, but the transition is smeared over a large temperature range. The compound Ba(Ni 0.5Nb 0.5)O 3 (BNN) was prepared using a standard ceramic technique and identified by X-ray diffraction. The unit cell parameter was found to be 4.054 Å with cubic structure. The dielectric, pyroelectric and electrical conductivity of the compound were studied under different poling conditions at, below and above the Curie temperature. The Devonshire phenomenological theory may be applied successfully to account for the experimental measurement of the dielectric and pyroelectric properties in the temperature range 27–400°C. From the pyroelectric measurement, the temperature dependence of the spontaneous polarization was found to be 5.43×10 −8C cm −2 at room temperature. The dielectric constant is found to be maximum at the Curie temperature. The compound was found to exhibit n-type and p-type semiconductor behaviour, respectively, below and above T c. The activation energy in the ferroelectric and paraelectric regions was obtained from electrical conductivity measurements. The pyroelectric measurements showed enhancement of the pyroelectric coefficient and spontaneous polarization values due to different poling conditions.