Phase stabilization and electrical characterisation in the pseudo-binary system Bi2ZrO5–Bi2VO5.5−δ

The pseudo-binary system Bi2ZrO5–Bi2VO5.5−δ has been investigated by X-ray powder diffraction and ac impedance spectroscopy, beyond the BIMEVOX composition stabilization region. Compositions of general formula xBi2ZrO5:(1−x)Bi2VO5.5−δ (0.22≤x≤1.00) were prepared by conventional solid state synthesis. A number of discrete phases were identified in the composition range studied. We have previously shown that a tetragonal γ-BIMEVOX phase is stable up to around x=0.20. In the range x=0.22–0.50 the BIMEVOX phase is gradually replaced by Bi8V2O17 leaving unreacted ZrO2. At x=0.60 Bi23V4O44.5 is stabilized. A tetragonally distorted fluorite phase is observed at x=0.70 and a cubic δ-Bi2O3 type phase in the range 0.80≤x≤0.90. The crystal structure parameters for the tetragonal fluorite type phase are presented. A maximum of conductivity at both high and low temperature was observed for the x=0.80 composition with σ=2.62×10−5 S cm−1 at 300 °C and σ=1.03×10−2 S cm−1 at 600 °C.