The Ni(III) perovskites: synthesis under high oxygen pressures and physico-chemical properties

The synthesis of new perovskite TlNiO3 and a comparative study with TNiO3 (T=rare earth or yttrium) have been performed. TlNiO3 was synthesized under high pressure. The domain of pressure and temperature conditions required for obtaining pure TlNiO3 is very narrow (8 GPa≤P, 650≤T≤700°C). The unit cell volume of TlNiO3 shows a large deviation from the relationship between effective ionic radii and unit cell volume for TNiO3 (T=rare earth or yttrium). Temperature dependence of magnetic susceptibility of TlNiO3 underlines an antiferromagnetic behavior with TN=100 K. The structural and magnetic behavior are attributed to the strong covalency of Tl(III)–O bond.