Metastable magnesium titanate phases synthesized in nanometric systems Academic Article uri icon

abstract

  • When heating mixtures of conventional magnesia and titania powders, geikielite (MgO. TiO2) appears first at about 600°C; only above 1200–1300°C is either qandilite (2MgO. TiO2) or karrooite (MgO. 2TiO2) formed, depending on whether MgO or TiO2 is in excess. A different behaviour pattern is observed when starting from nanometre precursors, consisting of hydroxides of magnesium and itanium, which lose water on heating to about 400°C, yielding nanocrystalline oxides. Coprecipitated nanometre precursors yield at 600°C qandilite, geikielite or karrooite, depending on the relative stoichiometries of magnesia and titania in the precursor powder. At higher temperatures, up to 1200°C geikielite is the only titanate formed, and only above 1300°C does qandilite or karrooite reappear, depending on the stoichiometry of the original mixture. Only karrooite is formed when independently prepared nanometre precursors of magnesia and titania are mixed together and heated to temperatures as low as 400°C and up to 6...

publication date

  • January 1, 1997