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

A perovskite-like phase of lanthanum magnesium niobate, La(Mg2/3Nb1/3)O-3 ( 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. Mor eover, particle size distribution, morphology, phase composition and crysta l structure have been determined via laser diffraction, SEM and TEM/EDX, re spectively. A combination of X-ray and electron diffraction studies has dem onstrated that heterogeneous powders are produced, with the presence of an MgO-rich phase and varying Mg/Nb ratios within the parent phase of LMN. Min or phases have also been identified as LaNbO4, La3NbO7. MgO, Mg4Nb2O9 and L a2O3, with their concentrations decreasing with rising calcination temperat ure. X-ray and electron diffraction data are supportive of monoclinic symme try in the parent LMN phase. (C) 2000 Elsevier Science Ltd. All rights rese rved.