Facile Synthesis of Perovskite-Structured Powders Using Barite–Celestite Ore under Hydrothermal Alkaline Conditions

Abstract

Barite–celestite (BC) crystals were treated in highly concentrated alkaline hydrothermal fluid (5 M KOH) coexisting with a Ti(OH)4·4.5H2O gel to produce SrTiO3 particles between 150 and 250 °C for several intervals between 6 h and 96 h. The BC transformation was initiated at a lower temperature (150 °C) and the total precursors consumption was completed at 250 °C for 96 h, resulting only in the crystallization of SrTiO3 particles. Different temperatures of reaction (≤200 °C) lead to variations in morphology and particle size of the SrTiO3. The crystal growth of faceted cubic agglomerates was achieved at 250 °C, and it is provoked by the Oswald ripening mechanism. The release of barium to the hydrothermal fluid from the precursor occurred simultaneously with the transformation process. A low value of activation energy required for the single-step transformation of the BC plates into SrTiO3 particles was observed (26.33 kJ mol–1), under static hydrothermal conditions.