SYNTHESIS AND CRYSTALLOCHEMICAL CHARACTERIZATION OF THE BI(3)RE(5)O(12)-TYPE PHASES

A series of Bi(3)(+3)RE(5)O(12)-type phases (RE = Y, La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Yb, Lu) has been prepared in air at 950 degrees C and characterized by X-ray powder diffraction acid density and valence measurements performed on single-phase samples. With the exception of the Er, Yb, and Lu varieties, the characteristic feature of the series is rhombohedral symmetry. The lattice parameters of the individual phases depend on the RE element and are within the intervals a = 3.755-3.959 Angstrom and c = 9.482-9.964 Angstrom (hexagonal setting). Traces of very weak superstructure peaks indicate a possible unit cell multiplication. The series is stable in air and exhibits a comparatively wide compositional interval centered around the Bi(3)RE(5)O(12) stoichiometry. (C) 1995 Academic Press, Inc.