SUBSOLIDUS PHASE-RELATIONS IN BIO3 2-GDO3/2-CUO SYSTEM/

The subsolidus phase relations of BiO3/2-GdO3/2-CuO ternary systems, i ts binary systems and crystallographic parameters of compounds are inv estigated by X-ray powder diffraction. The room temperature section of the phase diagram of the BiO3/2-GdO3/2-CuO system can be divided into four two-phase regions and six three-phase regions. No ternary compou nd was found. There exists three solid solutions (theta, alpha and gam ma) in the (BiO3/2 )(1-x)-(GdO3/2)(x) system. The solid solution theta (0.03 less than or equal to x less than or equal to 0.09) has space g roup P (4) over bar 2(1)c, the solid solutions alpha (0.1 less than or equal to x less than or equal to 0.12) and gamma (0.58 less than or e qual to x less than or equal to 0.7) have space group R (3) over bar m with lattice parameters n=3.9590(7) Angstrom, and c=27.895(5) Angstro m for Bi9GdO15(alpha phase) and a=3.8174(5), c=9.5445(2) Angstrom for Bi2Gd3O7.5 (gamma phase). For Bi2Gd3O7.5, the Rietveld structure refin ement reveals that Bi/Gd atoms occupy the 3a site statistically, O ato ms and vacancies occupy the 6c site.