Phase stability and ionic conductivity in bismuth lead (antimony) oxide

Abstract

Ionic conductivity was measured on (Bi 1− xSb x) 5Pb 8O 17 for x=0 to 0.2, from room temperature to 600°C, in air. At x=0, X-ray analysis and differential thermal analysis (DTA) showed that 3 distinct phase-regions were present in the material. At room temperature, a tetragonal β 2-phase which decomposed to a mixed state (including the stoichiometric Bi 8Pb 5O 17) at approximately 500°C, which further decomposed, at 590°C into the high ionic conducting cubic β-phase. Increasing x caused a lowering of the temperature that the β 2-phase decomposed into the mixed state (with a drop in the conductivity of the mixed state) but, in general, caused an increase in the temperature of the β-phase formation. This paper describes the effect on the phase and ionic conductivity of substituting zero to 20% Sb for Bi and 10% substitutions of Dy, Gd and Tm for Bi. Ionic conductivity was high for all these materials, but was reduced below that of the undoped material in the order Sb<Tm<Gd<Dy< undoped. However, Sb substitutions at concentrations as low as 2.5 mol% improved the mechanical integrity of the material over that of the undoped alloy.