Phase relations in the Na2MoO4–Cs2MoO4 and Na2MoO4–Cs2MoO4–ZnMoO4 systems, crystal structures of Cs3Na(MoO4)2 and Cs3NaZn2(MoO4)4

Zolotova, E.S. Phase relations in the Na2MoO4–Cs2MoO4 and Na2MoO4–Cs2MoO4–ZnMoO4 systems, crystal structures of Cs3Na(MoO4)2 and Cs3NaZn2(MoO4)4 / E.S. Zolotova, V.N. Yudin, S.F. Solodovnikov, E.G. Khaikina, O.M. Basovich, I.V. Korolkov, I.Yu. Filatova // J. Solid State Chem. – 2016. – V. 233. – P. 23–29. https://doi.org/10.1016/j.jssc.2015.10.008 (IF JCR- 2.299; Q2).

The phase diagram of the Na2MoO4-Cs2MoO4 system was reinvestigated and a new intermediate compound, Cs3Na(MoO4)(2), melting incongruently at 510 degrees C was found. Its crystal structure (a=6.3461(2), c=8.2209(3) angstrom, sp. gr. P (3) over bar m1, Z=1, R=0.0131) belongs to the glaserite type. Taking into account these data, the subsolidus phase relations of the system Na2MoO4-Cs2MoO4-ZnMoO4 was studied at 420 degrees C. The filling vacancies in the tetrahedral Zn position of the Cs6Zn5(MoO4)(8) structure (sp. gr. 1 (4) over bar 3d, Z=2) following the scheme Zn2+ +square -> 2Na(+) was established to result in the continuous solid solution Cs6Zn5-x square Na-1-x(2x)(MoO4)(8) (0 <= x <= 1). With increasing the x value, the cubic lattice parameter of the solid solution increases linearly while its melting point decreases that testifies to destabilization of the Cs6Zn5(MoO4)(8) structure by a progressive Na+ insertion. In the structure of Cs3NaZn2(MoO4)(4) (a=12.3134(1) angstrom, R=0.0121), Mo04 and (Zn2/3Na1/3)O-4 tetrahedra share corners to form an open 3D framework. The cesium ions are disordered around the centers of the cuboctahedral cavities of the framework to form "clusters" of the central Cs(1) and four disordered Cs(2) positions.