Synthesis of MgTiO3 and Mg4Nb2O9 using stoichiometrically excess MgO

MgTiO3 and Mg4Nb2O9 phases with an ordered corundum type structure were synthesised by reacting MgO and TiO2 or Nb2O5 together with addition of excess MgO with 1:1 and 4:1 stoichiometry. Moreover, a minor amount of MgTi2O5 and MgNb2O6 phases were also formed. It is shown that the formation of these additional phases can be suppressed by the addition of a stoichiometric excess of MgO, which can subsequently be removed after the reaction by treating with dilute mineral acid, thus forming pure MgTiO3 and Mg4Nb2O9. 16 refs.