CRYSTALLINE TRANSFORMATION OF TI-B-O, AL-TI-B-O, SI-TI-B-O AND AL-SI-TI-B-O BY THERMAL TREATMENTS

The thermal transformations of Ti-B-O, Al-Ti-B-O, Si-Ti-B-O and Al-Si-Ti-B-O have been investigated using the methods of thermal analysis and X-ray powder diffraction. The materials are a crystalline series of TiO2 with partial replacement of titanium by the elements, aluminium, boron and silicon. The anatase form of the materials was transformed to the rutile form at 520 approximately 680-degrees-C for Ti-B-O, 880 approximately 950-degrees-C for Al-Ti-B-O, 1080 approximately 1280-degrees-C for Si-Ti-B-O and 1180 approximately 1330-degrees-C for Al-Si-Ti-B-O. The rate constant for the anatase-rutile transformation of Ti-B-O was 6.908 x 10(-3) min-1 under isothermal conditions at 680-degrees-C. Analysis of the kinetic data obtained by differential thermal analysis (DTA) gave the activation energy for transformation of anatase into rutile as 663.7 Kcal mol-1 for Al-Ti-B-O. The lattice parameters for the compounds studied at various temperatures were calculated by least-squares fitting of the X-ray powder diffraction data.