Crystallization of magnesium niobate from mechanochemically derived amorphous phase

The effect of high-energy ball milling and subsequent annealing on the mixture of MgO and Nb2O5has been investigated. X-ray diffraction (XRD) measurement indicates that an amorphous phase is produced after milling for 5 h, while traces of MgNb2O6crystallized from the amorphous phase during prolonged milling. Significant crystallization of MgNb2O6from the amorphous state is observed after annealing at 500 °C, while the reaction of the remaining MgO and Nb2O5does not take place at this temperature. Single phase MgNb2O6 can be achieved for all the milled samples at 700 °C. No significant grain growth is observed when the milled powders were annealed at temperature below 900 °C. Almost fully dense MgNb2O6ceramics are obtained after annealing at 1100 °C from the as-milled powders.