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 unde r high pressure. The domain of pressure and temperature conditions required for obtaining pure TlNiO3 is very narrow (8 GPa less than or equal to P, 6 50 less than or equal to T less than or equal to 700 degreesC). The unit ce ll volume of TlNiO3 shows a large deviation from the relationship between e ffective ionic radii and unit cell volume for TNiO3 (T = rare earth or yttr ium). Temperature dependence of magnetic susceptibility of TlNiO3 underline s an antiferromagnetic behavior with T-N = 100 K. The structural and magnet ic behavior are attributed to the strong covalency of TI(III)O bond. (C) 20 00 Published by Elsevier Science Ltd.