Phase formation in the Rb2MoO4-Li2MoO4-Hf(MoO4)2 system and the crystal structure of Rb5(Li1/3Hf5/3)(MoO4)6

Three ternary molybdates have been found in the Rb2MoO4-Li2MoO4-Hf(MoO4)(2) system: Rb-5(Li1/3Hf5/3)(MoO4)(6) (S-1), Rb3LiHf2(MoO4)(6) (S-2), and RbLiHf(MoO4)(3) (S-3). The compositions of the first two molybdates have been confirmed by matching isostructural analogs. The structure of phase S, has been determined (a CAD4 diffractometer, 3532 reflections, a = 10.659(2) Angstrom, c = 38.241(8) Angstrom, Z = 6, space group R3c, R = 0.034). In structure S-1, Li and Hf atoms randomly occupy cation sites with octahedral coordination in the proportion 1 5, whereas Rb atoms are positioned in large voids of the tetrahedral-octahedral framework. Compound S-2 (a 5.805(1) Angstrom, c = 7.533(2) Angstrom, space group P (3) over bar m1, Z = 1) belongs to the KAl(MoO4)(2) structure type with random substitution of Li and Hf atoms for Al atoms in the proportion 1 : 2.