A method based on hydrothermal treatments is described for increasing the surface area of sintered ABO3-type perovskite oxides. Influence of hydrothermal treatments, such as water treatment at 125–300°C under autogeneous pressure and steam treatment at 350–800°C, to low surface area (or sintered) LaCoO3 and LaMnO3 perovskite oxides on their surface properties (viz. surface area, crystal size and morphology and surface La/(Co or Mn) ratio) and also catalytic activity in complete combustion of methane at different temperatures (450–600°C) has been thoroughly investigated. The hydrothermal treatments result in the activation of the perovskite oxides by increasing their surface area very markedly.
