On the relaxation/transformation of NiO-dissolved TiO2 condensates with fluorite-type derived structures

Nd-YAG-laser pulse irradiation of clamped Ni/Ti plates in oxygen was employed to synthesize fluorite-type (f) derived TiO2 condensates dissolved up to 5 at% Ni2+ of the cations. The nanocondensates less than 20 nm in size are nearly cubo-octahedral in shape and tended to transform martensitically to monoclinic (m) baddeleyite-type following the crystallographic relationship (100)f//(110)m; [001]f//[001]m. The condensates twice larger in size, with considerable matrix constraint, are nearly spherical in shape and consist of mosaic m-twin variants following complicated crystallographic relationships with each other and with the relic f-phase: (010)f//(image)m; [001]f//[001]m. The charge and volume compensating oxygen vacancies due to NiO dissolution in the dense TiO2 condensates could facilitate the relaxation and amorphization process.