Synthesis, crystal structure, and structural conversion of Ni molybdate hydrate NiMoO4·nH2O

The synthesis and crystal structure of NiMoO4·nH2O 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) Å, b=6.8900(2) Å, c=9.2486(2) Å, α=76.681(2)°, β=83.960(2)°, γ=74.218(2)°. Its ideal chemical composition was NiMoO4·3/4H2O rather than NiMoO4·1H2O. Under hydrothermal conditions the hydrate turned directly into α–NiMoO4 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.