Phase and morphology evolution of magnesium niobate powders synthesized by solid-state reaction

Magnesium niobate (MgNb2O6; MN) powders have been prepared and characterized by TG-DTA, XRD, SEM and EDX techniques. The effect of calcination temperature, dwell time and heating/cooling rates on phase formation, morphology and chemical composition of the powders are examined. The calcination temperature and dwell time have been found to have a pronounced effect on the phase formation of the calcined magnesium niobate powders. It has been found that the minor phases of unreacted MgO and Nb2O5 phases tend to form together with the columbite-type MgNb2O6 phase, depending on calcination conditions. It is seen that optimisation of calcination conditions can lead to a single-phase MgNb2O6 in an orthorhombic phase. Higher calcination times and heating/cooling rates clearly favoured particle growth and the formation of large and hard agglomerates. (C) 2004 Published by Elsevier B.V.