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

•The phase equilibria in Na2MoO4–Cs2MoO4 system were reinvestigated.•Subsolidus phase relations of Na2MoO4–Cs2MoO4–ZnMoO4 system was studied.•The complete solid solutions Сs3NaZn2(MoO4)4–Cs6Zn5(MoO4)8 were found.•Crystal structures of Cs3Na(MoO4)2 and Сs3NaZn2(MoO4)4 were determined.•Cesium ions are disordered in Сs3NaZn2(MoO4)4 structure.

The phase diagram of the Na2MoO4–Cs2MoO4 system was reinvestigated and a new intermediate compound, Cs3Na(MoO4)2, melting incongruently at 510 °С was found. Its crystal structure (a=6.3461(2), c=8.2209(3) Å, sp. gr. P3¯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 °С. The filling vacancies in the tetrahedral Zn position of the Cs6Zn5(MoO4)8 structure (sp. gr. I  4¯ 3d, Z=2) following the scheme Zn2++◻→2Na+ was established to result in the continuous solid solution Сs6Zn5−x◻1−xNa2x(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 Сs3NaZn2(MoO4)4 (а=12.3134(1) Å, R=0.0121), MoO4 and (Zn2/3Na1/3)O4 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.

Graphical abstractGraphical abstract legend structures of studied compounds Cs3Na(MoO4)2 and Cs3NaZn2(MoO4)4.Figure optionsDownload full-size imageDownload as PowerPoint slide