Preparation and microstructure characterization of m-ZrO 2–20 mol% a-TiO 2 ball milled mixture by Rietveld method

Abstract

High energy ball milling of monoclinic (m) ZrO 2–20 mol% anatase (a) TiO 2 mixture at different durations, results in formation of m-ZrO 2–a-TiO 2 solid solution from which the nucleation of nanocrystalline cubic (c) ZrO 2 polymorphic phase sets in. Post-annealing of 12 h ball milled sample at different elevated temperatures for 1 h results in almost complete formation of c-ZrO 2 phase. Microstructure of the unmilled, all ball milled and post-annealed samples has been characterized by employing Rietveld's X-ray powder structure refinement methodology. Particle size, r.m.s. lattice strain, lattice parameters, molar fraction etc. of individual phases have been estimated from Rietveld analysis and are utilized to interpret the results. Cubic phase is presumed to have formed on the (001) of the m-ZrO 2–a-TiO 2 solid solution. In course of milling, most dense (111) of cubic lattice became parallel to most dense ( 1 ̄ 11) of monoclinic lattice due to lattice orientation effect. Annealing of 12 h ball milled sample at 773, 873, 973 and 1073 K each for 1 h duration results in reduction of lattice strain to a considerable amount and negligible increase in particle size of both the m- and c-ZrO 2 phases. It suggests that almost fully stabilized nanocrystalline c-ZrO 2 can also be formed by adding a tetravalent solute to m-ZrO 2.