CRYSTAL-STRUCTURE OF TBTA3O9 AND EUTA3O9 AND THEIR CONTINUOUS SOLID-SOLUTION CHARACTERIZATION

The double oxides of the lanthanides and tantalum LnTa(3)O(9) (Ln = Tb , Eu) were synthesized by solid state reaction and characterized by X- ray powder diffraction. EuTa3O9 is orthorhombic, with space group Pmmm , a = 3.8689(3) Angstrom, b = 3.8837(2) Angstrom, c = 7.7972(1) Angstr om, V = 117.158 Angstrom(3), Z = 2/3; TbTa3O9 is tetragonal, with spac e group P4/mmm, a = 3.8603(2) Angstrom, c = 7.7804(3) Angstrom, V = 11 5.943 Angstrom(3), Z = 2/3. The continuous solid solution Tb1-xEuxTa3O 9 were obtained and characterized. Cell parameters and density measure ments of 10 specimens of solid solutions as a function of x are presen ted. (C) 1996 Academic Press, Inc.