The effect of mechanical activation on formation of calcium titanate (CaTiO3) from calcined mixtures of CaCO3 and TiO2 was studied by monitoring the course of this solid-state reaction by variable temperature in situ X-ray diffraction (XRD) experiments, scanning electron microscopy (SEM) and dilatometry. Two equimolar mixtures of powdered CaCO3 and TiO2 were prepared: one was mechanically activated by grinding in a high energy vibro-mill. A total of 32 X-ray diffraction data sets for each sample, collected between 30 and 1100 degreesC, were analyzed by multiphase Rietveld refinement. Quantitative phase analysis and microstructure analysis obtained from X-ray diffraction are correlated to results of scanning electron microscopy and dilatometry. In the non-activated sample, small quantities of the reactants remain in the product until 1100 degreesC. In the activated sample, the reaction results in pure CaTiO3 at 920 degreesC. (C) 2003 Elsevier Science Ltd. All fights reserved.