Mechanochemical synthesis of ZrTiO₄ precursor from inhomogeneous mixed gels

Effects of vibration ball-milling of a powdered mixture of two gels, prepared from mixing ZrO₂ and TiO₂ sols, on crystallization processes during heating are studied in order to elucidate enhanced mechanochemical reactions with the aid of hydroxyl groups. TiO₂ (anatase) and ZrO₂ (tetragonal) crystallized at 698 K and 712 K, respectively, when heatingnon-milled gel mixture at 10 K min^-1 in air. Few reactions between the two phases were detected below 1023 K. After vibro-milling a powdered gel mixture at room temperature for 3 to 30 h, ZrTiO₄ (orthorhombic) crystallized directly from non-crystalline precursors on heating to 1023 K. The fraction of crystallized ZrTiO₄, determined by Raman spectroscopy, increased linearly with increasing the index of micro-homogeneity for non-heated gels. We suggest that short-range ordering of ZrTiO₄ rather than crystallization of individual oxides occurs through the non-thermal atomic movement between different metallic species under mechanical stress.