# Nickel(II) titanate

Nickel(II) titanate, also known as nickel titanium oxide, is an inorganic compound with the chemical formula NiTiO$_3$. It is a coordination compound between nickel(II), titanium(IV) and oxide ions. It has the appearance of a yellow powder. Nickel(II) titanate has been used as a catalyst for toluene oxidation. Nickel(II) titanate furthermore has many different names such as nickel titanium oxide; titanium nickel oxide; nickel titanium trioxide.

## Molecular and crystal structure

Nickel(II) titanate crystallizes at 600 °C and is stable at room temperature and normal pressure in an ilmenite structure with rhombohedral R3 symmetry. Nickel(II) titanate's rhombohedral structure has layers of Ni and Ti alternate along the rhombohedral axis with O layers between them. The XRD data supports nickel(II) titanate's ilmenite structure with its rhombohedral symmetry. Other descriptions of nickel(II) titanite's Illemite structure consists of a pseudo close packed hexagonal array of O$^{2−}$ ions with two thirds occupied by an ordered hexagonal like cation. The Average crystallites size for nickel(II) titanate was estimated at 42 nm with lattice constants of a = 5.032 Å, b = 5.032 Å, c = 4.753 Å. The structure was established by using X-ray power intensities.

## Synthesis

There are several methods of synthesis for nickel(II) titanate. The first method involves nickel(II) titanate's melting temperature of over 500 °C at which its precursor decomposes to give nickel(II) titanate as a residue. The second method involved using enthalpy and entropy on the reaction to synthesize nickel(II) titanate through its phase transition.
Nickel(II) titanate was synthesized using the polymeric precursor method. This involved spontaneous combustion of Ti(OCH(CH$_3$)$_2$)$_4$ with Ni(NO$_3$)$_2$·6H$_2$O and C$_3$H$_7$NO$_2$ in a molar ratio of 1:1:20 in isopropyl alcohol solution. The product of nickel(II) titanate was calcinated from the precursor at 600 °C for 3 hours.
Nickel(II) titanate was also formed by heating NiO and TiO$_2$ at 1350 °C for three hours. Then it was then cooled until room temperature.
NiO + TiO$_2$ + (heat) → NiTiO$_3$
A single-source heterobimetallic complex Ni$_2$Ti$_2$(OEt)$_2$(μ-OEt)$_6$(2,4-pentanedionate)$_4$ was synthesized and underwent thermal decomposition at 500 °C to give NiTiO$_3$ residue.

## Properties

By doping the NiTiO$_3$ with Ga$_2$O$_3$, the anomalous increase of the electrical conductivity is shifted to lower temperatures.

## Applications

Due to nickel(II) titanate's brilliant yellow color and high UV-vis-NIR reflectance, it has the potential to serve as a pigment for building coating. Ilmenite-type NiTiO$_3$ are well known as functional inorganic materials with wide application in electronic materials, including electrodes of solid fuel cells, gas sensors, chemical catalysts and so on due to their high static dielectric constants, weak magnetism and semiconductivity. NiTiO$_3$ as a semiconductor has excellent catalytic activity due to its absorption bands. Analysis of the band structures and density of states have implied that nickel(II) titanate has immense potential in the areas of high-density data storage, gas sensor data and integration in circuit devices. NiTiO$_3$ has even been utilized as a catalyst in toluene oxidation.
It is used as a yellow pigment.
MTiO$_3$ (M= Ni, Fe, Mn) compounds have received attention as possible candidates for multiferroic materials capable of magnetization through application of electric field.
Through an experiment to see if NiTiO$_3$ could serve as a catalyst for toluene oxidation in comparison to NiFe$_2$O$_4$, NiTiO$_3$ achieved greater results than its experimental counterpart in oxidating toluene.