Perovskite-type oxides synthesized by reactive grinding Part I. Preparation and characterization

Perovskite-type materials LaCoO3 and LaCoFeO3 were prepared from their component oxides using mechano-synthesis, by a new method of preparation designated as reactive grinding. When grinding additives are used, the perovskites generated via this process are of unprecedently high specific surface area (>100 m(2)/g) and their surface chemical properties are of particular interest. The perovskite surface shows a large concentration of surface OHs (due to the low grinding temperature) which upon calcination leads to reformation of the materials lattice. The presence of oxygen during calcination initiates a competitive process, which stabilizes sites with an excess of electronic charge, yielding reduced Co sites upon oxygen desorption (Co2+). XPS analysis illustrates an increase in these reduced Co2+ ion concentration with calcination temperature. At high calcination temperature (>673 K), TPD studies show the release of beta -oxygen originating from the bulk. (C) 2001 Elsevier Science B.V. All rights reserved.