Effect of mechanical activation on the preparation of SrTiO3 and Sr2TiO4 ceramics from the solid state system SrCO3-TiO2

By thermoanalysis (TGA and DSC) and X-ray powder diffraction it has been shown that the compounds SrTiO and Sr2TiO4 can be prepared by mechanical activation of, respectively, 1:1 and 2:1 SrCO –TiO (rutile) mixtures followed by annealing for 12 h at 800–8508C. These compounds could not be obtained by heating the physical mixtures to temperatures as high as 1000 °C. Moreover, the enthalpies of the reactions leading from Sr carbonate and rutile to the formation of these compounds have been determined. By combining these data with the enthalpy of SrCO decomposition, also obtained in this work, the enthalpies of formation of SrTiO and Sr2TiO4 have been calculated. On the contrary, no Sr3Ti2O7 was shown to form, by the same annealing procedure, when starting from a mechanically activated mixture. DSC and XRD results agree in indicating that a mixture of Sr TiO and SrTiO forms instead.