Phase Formation in the Li2MoO4-A2MoO4-NiMoO4 (A = K, Rb, Cs) Systems, the Crystal Structure of Cs2Ni2(MoO4)3, and Color Characteristics of Alkali-Metal Nickel Molybdates

The subsolidus regions of the Li2MoO4-A(2)(+)MoO(4)-NiMoO4 (A(+) = K, Rb, Cs) systems at 510 degrees C have been triangulated by the intersecting-joins method. The A(2)MoO(4)-Li2Ni2(MoO4)(3), Li2MoO4-A(2)Ni(2)(MoO4)(3), A(2)Ni(2)(MoO4)(3)-Li2Ni2(MoO4)(3) (A = K, Rb, Cs), and ALiMoO(4)-A(2)Ni(2)(MoO4)(3) (A = K, Rb) joins have been investigated. The subsolidus phase formation study has also been completed by spontaneous flux crystallization. No triple salts have been identified, but only compounds belonging to the boundary binary systems. The crystal structure of Cs2Ni2(MoO4)(3) (a = 10.7538 angstrom, Z = 4, space group P2(1)3, R = 0.0082) belonging to the langbeinite type has been determined. It is built of a three-dimensional framework of vertex-sharing MoO4 tetrahedra and NiO6 octahedra and cesium ions occupying large out-of-framework cavities. All alkali-metal nickel molybdates are yellow. These compounds are usable as pigments, as judged from their reflection spectra and calculated color characteristics, namely, colorfulness (C), lightness (L), and hue (H).