The perovskite system La(Mg2/3Nb1/3)O3: I. Synthesis, formation and characterisation of powders

A perovskite-like phase of lanthanum magnesium niobate, La(Mg2/3Nb1/3)O3 (LMN) has been synthesised by a mixed oxide synthetic route. Both magnesium oxide and magnesium carbonate hydroxide pentahydrate have been investigated as magnesium precursors, with the formation of the LMN phase investigated as a function of calcination temperature and dwell time by DTA and XRD. Morever, particle size distribution, morphology, phase composition and crystal structure have been determined via laser diffraction, SEM and TEM/EDX, respectively. A combination of X-ray and electron diffraction studies has demonstrated that heterogeneous powders are produced, with the presence of an MgO-rich phase and varying Mg/Nb ratios within the parent phase of LMN. Minor phases have also been identified as LaNbO4, La3NbO7, MgO, Mg4Nb2O9 and La2O3, with their concentrations decreasing with rising calcination temperature. X-ray and electron diffraction data are supportive of monoclinic symmetry in the parent LMN phase.