Nickel tungstate is an inorganic compound of nickel, tungsten and oxygen, with the chemical formula of NiWO4.
Preparation
Nickel tungstate can be prepared by the reaction of nickel(II) nitrate and sodium tungstate:A. Kuzmin, J. Purans, R. Kalendarev: Local structure and vibrational dynamics in NiWO4. In: Ferroelectrics. 258, 2001, S. 21, .
Ni(NO3)2 + Na2WO4 → NiWO4 + 2 NaNO3
Nickel tungstate can also be prepared by the reaction of nickel(II) oxide and tungsten(VI) oxide.
It can also be obtained by the reaction of ammonium metatungstate and nickel(II) nitrateJ.M. Quintana-Melgoza, J. Cruz-Reyes, M. Avalos-Borja: Synthesis and characterization of NiWO4 crystals. In: Materials Letters. 47, 2001, S. 314, . or from the reaction of sodium tungstate, nickel(II) chloride and sodium chloride.R. O. Keeling: The structure of NiWO4. In: Acta Crystallographica. 10, S. 209, .
Nickel tungstate undergoes a phase transition at 700 °C.
Properties
Nickel tungstate is a light brown, odourless solid that is insoluble in water. The amorphous form is green and the polycrystalline form is brown. It crystallizes in the wolframite crystal structure of the monoclinic crystal system with space group P2/c (No. 13). The compound is antiferromagnetic.C. Wilkinson, Μ. J. Sprague: The magnetic structures of NiWO4 and CoWO4. In: Zeitschrift für Kristallographie - Crystalline Materials. 145, 1977, .Alexei Kuzmin, Aleksandr Kalinko, Robert Evarestov: First-principles LCAO study of phonons in NiWO4. In: Open Physics. 9, 2011, .
Applications
Nickel tungstate has no commercial uses. It has been examined as a photocatalyst, in humidity sensors, and in dielectric resonators. It is also considered as a "promising" cathode material for asymmetric supercapacitors.
Other compounds Nickel tungstate forms compounds with ammonia, such as NiWO4·2NH3·H2O which are cyan crystals,Nickel: sect. 1-2. Coordination compounds with neutral and inner-complex-forming ligands (Verlag Chemie, 1968), page 109. Retrieved 15 Apr 2021. NiWO4·4NH3 which are green crystals,Bulletin de la Société chimique de France (Société chimique de France; Masson, 1921), page 1487. Retrieved 28 Feb 2021. NiWO4·5NH3·H2O as dark blue crystals or anhydrous NiWO4·6NH3 which is crystalline purple, while the octahydrate of hexamine is dark blue.
References