Phase stabilization and electrical characterisation in the pseudo-binary system Bi2ZrO5–Bi2VO5.5−δ
Abstract The pseudo-binary system Bi 2 ZrO 5 –Bi 2 VO 5.5− δ has been investigated by X-ray powder diffraction and ac impedance spectroscopy, beyond the BIMEVOX composition stabilization region. Compositions of general formula x Bi 2 ZrO 5 :(1− x )Bi 2 VO 5.5− 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 Bi 8 V 2 O 17 leaving unreacted ZrO 2 . At x =0.60 Bi 23 V 4 O 44.5 is stabilized. A tetragonally distorted fluorite phase is observed at x =0.70 and a cubic δ-Bi 2 O 3 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.