The pseudo-binary system Bi2ZrO5-Bi2VO5.5-delta has been investigated by X-ray powder diffraction and ac impedance spectroscopy, beyond the BIMEVOX composition stabilization region. Compositions of general formula xBi(2)ZrO(5):(1-x)Bi2VO5.5-delta (0.22less than or equal toxless than or equal to1.00) 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 gamma-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 delta-Bi2O3 type phase in the range 0.80less than or equal toxless than or equal to0.90. 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 sigma=2.62 x 10(-5) S cm(-1) at 300 degreesC and sigma=1.03 x 10(-2) S cm(-1) at 600 degreesC. (C) 2004 Elsevier B.V. All rights reserved.