Phase equilibria in the Tl2MoO4-Pr2(MoO4)3-Hf(MoO4)2 system and crystal structure of TlPr(MoO4)2

Subsolidus (450–480°C) phase relations in the Tl2MoO4-Pr2(MoO4)3-Hf(MoO4)2 system have been studied by X-ray diffraction. The system has been shown to contain molybdates with the compositions Tl5PrHf(MoO4)6 (5: 1: 2), TlPrHf0.5(MoO4)3 (1: 1: 1), and Tl2PrHf2(MoO4)6.5 (2: 1: 4). Single crystals of the double molybdate TlPr(MoO4)2 have been grown for the first time from high-temperature solutions through spontaneous nucleation, and their crystal structure has been determined: tetragonal symmetry, sp. gr. P4/nnc, a = 6.3170(1) A, c = 9.5529(2) A, V = 381.204(12) A3, Z = 2.