Extended versus small defect-equilibria in non-stoichiometric rutile. I. Dissolution and re-precipitation of extended defects observed by in-situ transmission electron microscopy

Abstract

Extended defects accomodating non-stoichiometry in rutiles reduced slightly to compositions of TiO1.9966, TiO1.9979, and TiO1.9986 are seen to dissolve in situ in an electron microscope using a goniometer at temperatures of up to 1000 °C. This allows to determine as directly as possible the stoichiometry dependence of the dissolution temperature, and hence the phase limits of nonstoichiometric TiO2−x. The defect structures formed during dissolution, and also the reprecipitation of extended defects upon cooling of the specimens to room temperature, are also studied. Dans un microscope electronique muni d'un porte-object chauffant jusqu' a des temperatures de 1000 °C environ, on a observe in situ la dissolution des defauts etendus accommodant la nonstoichiometrie de cristaux de rutile reduits aux compositions TiO1,9966, TiO1,9979 et TiO1,9986. Ceci a permis de determiner la temperature de dissolution en fonction de l'ecart a la stoichiometrie, et par la -měme la limite de la phase nonstoichiometrique TiO2−x aussi directement que possible. La structure des defauts formes durant la dissolution ainsi que la re-precipitation des defauts etendus (apres dissolution) ont ete egalement etudiees.