SYNTHESIS AND CRYSTALLOCHEMICAL CHARACTERIZATION OF THE TB1-XBIXSRO3 TYPE SOLID-SOLUTION

Solid solution of the Tb1-xBixSrO3 type was investigated under oxidizi ng sintering conditions. The domain of homogeneity was determined to b e within the range 0 less than or equal to x less than or equal to 0.3 3. Variations of lattice parameters as well as sample densities vs. th e substitution parameter x are given. The effective valency of Bi and Tb ions, (V) over bar((Tb,Bi)), remains invariant and is close to +4 t hrough the whole domain of homogeneity. The present data do not permit the exact variation of valencies of Bi and Tb ions to be separately r ecognized. However, the solubility limit found directly indicates a ne arly +5 valency of Bi ions and a variable valency of Tb ions, the latt er decreasing vs. x to the level of +3.5 characteristic for Tb4O7-the most stable terbium oxide in air. The possibility of a successful synt hesis of the hypothetical Tb+3Bi+5Sr2O6 is explored. (C) 1996 Academic Press, Inc.