The effects of vibration ball-milling of a mixture of two gels, prepared from mixing ZrO2 and TiO2 sols, on crystallization processes during heating are studied in order to determine enhanced mechanochemical reactions with the aid of hydroxyl groups. Data of differential thermal analysis (DTA) and X-ray diffractometry show that TiO2 (anatase) and ZrO2 (tetragonal) crystallized at 698 and 712 K, respectively, when a powdered gel mixture was heated to 1023 K to 10 K min-1 in air. No reactions between the two phases were detected. After vibro-milling a powdered gel mixture at room temperature for 3 to 30 h, a new exothermic DTA peak appeared around 950 K and ZrTiO4 (orthorhombic) was detected on heating to 1023 K. After vibro-milling, the compositional micro-homogeneity of non-heated gels was estimated from the fluctuations of elemental compositions in local areas using energy dispersive spectrometer with a 25 nm electron beam. The fraction of ZrTiO4 crystallized on heating the gels to 1023 K, determined by Raman spectroscopy, increased linearly with increasing the micro-homogeneity for non-heated gels. It is suggested that atomic movement and short-range ordering of ZrTiO4 rather than crystallization of individual oxides occur when applying mechanical stress to a powdered mixture of ZrO2 and TiO2 gels.
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Ceramics and Composites
- Condensed Matter Physics
- Materials Chemistry