PHASE STABILITY AND CONDUCTIVITY OF δ-Bi2O3 WITH MIXTURE OF YTTRIUM AND YTTERBIUM OXIDES

In this research Bi2O3 was doped with mixtures of 8, 10, 12 and 18 mol % of Y2O3 and Yb2O3 to stabilizing the δ-Bi2O3 phase using solid state reaction technique. Experimental samples were fabricated by isostatic pressing and sintering at 850 °C for 24 h. X-ray diffraction analysis detected cubic phase (δ-Bi2O3) as the sole stable crystalline phase in samples including 12 and 18 mol % of Y2O3 and Yb2O3.  The tetragonal phase was also observed in samples with 8 and 10% mol additives.  X-ray diffraction analyses on aged samples at 600 oC with 12 mol % additives revealed that the δ-Bi2O3 phase was transformed to the tetragonal polymorph form.  Results of ionic conductivity measurements showed that samples with 12 mol % additives (88 mol % Bi2O3, 8 mol % Y2O3 and 4 mol % Yb2O3) had a higher ionic conductivity than the other samples.