High-temperature X-ray structural, thermal and dielectric characteristics of ferroelectric Bi₂VO_5.5

Abstract

The X-ray powder diffraction, dielectric and thermal studies of bismuth vanadate (Bi₂VO_5.5) ceramic have been carried out as a function of temperature (300–900 K). The hightemperature X-ray studies, supported by differential scanning calorimetry, clearly demonstrate that Bi₂VO_5.5 undergoes two major phase transitions at ∼730 and ∼835 K. It was found that the one at 730 K is associated with both the ferroelectric and the crystallographic transition, while at 835 K, Bi₂VO_5.5 undergoes only the crystallographic transition. Anomalies in both the dielectric constant and specific heat curves have been observed at ∼ 730 and ∼ 835 K. The total heat, ΔQ, and entropy, ΔS, associated with the transition at 730 K were found to be higher than those at 835 K.