Nickel tungstate is an

inorganic compound In chemistry, an inorganic compound is typically a chemical compound that lacks carbon–hydrogen bonds, that is, a compound that is not an organic compound. The study of inorganic compounds is a subfield of chemistry known as '' inorganic chemist ...

of nickel, tungsten and oxygen, with the chemical formula of NiWO₄.

Preparation

Nickel tungstate can be prepared by the reaction of

nickel(II) nitrate Nickel nitrate is the inorganic compound Ni(NO3)2 or any hydrate thereof. The anhydrous form is not commonly encountered, thus "nickel nitrate" usually refers to nickel(II) nitrate hexahydrate. The formula for this species is written in two w ...

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 Tungsten(VI) oxide, also known as tungsten trioxide is a chemical compound of oxygen and the transition metal tungsten, with formula WO3. The compound is also called tungstic anhydride, reflecting its relation to tungstic acid . It is a light ye ...

. It can also be obtained by the reaction of ammonium metatungstate and

J.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 Nickel(II) chloride (or just nickel chloride) is the chemical compound NiCl2. The anhydrous salt is yellow, but the more familiar hydrate NiCl2·6H2O is green. Nickel(II) chloride, in various forms, is the most important source of nickel for chemi ...

and

sodium chloride Sodium chloride , commonly known as salt (although sea salt also contains other chemical salts), is an ionic compound with the chemical formula NaCl, representing a 1:1 ratio of sodium and chloride ions. With molar masses of 22.99 and 35.45 g ...

.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

supercapacitor A supercapacitor (SC), also called an ultracapacitor, is a high-capacity capacitor, with a capacitance value much higher than other capacitors but with lower voltage limits. It bridges the gap between electrolytic capacitors and rechargeable ba ...

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

{{Tungstates Nickel compounds Tungstates