THERMAL-EXPANSION AND ELECTRICAL-CONDUCTIVITY OF (BI2O3)(1-X)(PR2O11 3)(X) SOLID ELECTROLYTES/

The thermal expansion and electrical conductivity of (Bi2O3)(1-x)(Pr2O 11/3)(x), where x = 0.2, 0.3, 0.4 and 0.5, were studied in the tempera ture range 100-800 degrees C. Identification of the phases formed was performed by X-ray diffraction at room temperature. The beta-type rhom bohedral phase was confirmed for the samples with x=0.2, 0.3, and the LaOF-type rhombohedral phase for x=0.5. A mixture of the two phases wa s observed for x=0.4. A jump in both the thermal expansion and the ele ctrical conductivity curves for x=0.2, 0.3 and 0.4, at around 700 degr ees C, indicated the occurrence of a phase transition. The thermal exp ansion coefficient of the substituted compositions in the low temperat ure range was in all cases higher than that of pure Bi2O3, but it decr eased linearly with increasing Pr2O11/3 content. The LaOF-type structu re exhibited higher conductivity and lower activation energy values co mpared with the beta-type structure. The conductivity of the high temp erature phase decreased with increasing Pr2O11/3 content. (C) 1998 Els evier Science Limited. All rights reserved.