Nickel oxide, aka Ni2O3, is a green crystalline solid that is highly insoluble in water. It is used in ceramics, glass, and electronic components. Occasionally it is found free in nature, but most often it is produced in a laboratory. A number of million kilograms are produced annually.
The main advantage of nickel oxide is its thermal stability. This property makes it a suitable material for optics and magnets. Interestingly enough, it is also soluble in nitric acid. For this reason, it is widely used in the manufacturing of batteries. Other applications include optical components and laser diodes.
Despite its rarity, nickel oxide is an interesting material to study. X-ray spectroscopy and four-probe dc electronic conductivity measurements have revealed that the material is a semiconductor at a wide range of temperatures. Moreover, its amorphous structure enables it to act as a conductive material in a solid state environment. In addition, it may be of use in organic synthesis.
Compared to nickel oxide, a related compound is the nickel oxide hydroxide. Both are produced in aqueous solutions. However, the former is much more characterized. Besides, it probably doesn’t have the same novelty value.
Similarly, the nickel (III) oxide is not a newcomer in the field. For example, high Tc superconducting cuprates have been extensively studied. On the other hand, black nickel oxide is a useful colorant for glass, as well as for ceramic frits. As such, it has been used to make blue and yellow colors as well as fuel cell production.