Synthesis, crystal structure, and structural conversion of Ni molybdate hydrate NiMoO{sub 4}.nH{sub 2}O

The synthesis and crystal structure of NiMoO{sub 4}.nH{sub 2}O were investigated. The hydrate crystallized in the triclinic system with space group P-1, Z=4 with unit cell parameters of a=6.7791(2) A, b=6.8900(2) A, c=9.2486(2) A, {alpha}=76.681(2){sup o}, {beta}=83.960(2){sup o}, {gamma}=74.218(2){sup o}. Its ideal chemical composition was NiMoO{sub 4}.3/4H{sub 2}O rather than NiMoO{sub 4}.1H{sub 2}O. Under hydrothermal conditions the hydrate turned directly into {alpha}-NiMoO{sub 4} above 483 K, giving nanorods thinner than the crystallites of the mother hydrate. On the other hand, it turned into Anderson type of polyoxomolybdate via a solid-solution process in a molybdate solution at room temperature. - Graphical abstract: NiMoO{sub 4}.nH{sub 2}O crystallized in the triclinic system with space group P-1, and its ideal chemical composition was NiMoO{sub 4}.3/4H{sub 2}O rather than NiMoO{sub 4}.1H{sub 2}O.