The incorporation and the reducibility of Ni 2+ in MgTiO 3

Abstract

NixMg1−xTiO3 samples with x up to 0.20 have been examined by X-ray diffraction, reflectance, and ESR spectroscopy, magnetic susceptibility, and thermogravimetric determinations, to investigate the incorporation and the reducibility of Ni2+ in the MgTiO3 ilmenite-type structure. The formation of the NixMg1−xTiO3 solid solution is demonstrated by X-ray diffraction and ESR determinations. Reflectance spectra, magnetic susceptibility, and thermogravimetric measurements, which were also performed, cannot distinguish between a true solid solution and a mechanical mixture. The incorporation of Ni2+ causes a slight decrease of the volume of the MgTiO3 unit cell. The reduction by hydrogen of Ni2+ in the NixMg1−xTiO3 solid solutions takes place at approximately 700°;C with segregation of metallic nickel and TiO2. At higher temperatures TiO2 reacts with MgTiO3 giving MgTi2O5.