Synthesis and dielectric characterisation of lead magnesium niobate from precipitation and freeze-drying methods

Abstract

Lead magnesium niobate, Pb(Mg_1/3Nb_2/3)O₃ (PMN), has been prepared from aqueous nitrate solutions by freeze-drying and stepwise precipitation using an ammonia solution as the precipitant. Perovskite PMN powders with less than 5% pyrochlore phase were obtained when the resulting precursors were calcined at temperatures in the range of 800 to 1000 °C. They exhibited a rounded powder morphology and an average agglomerate size of <1.0 µm. Freeze-dried PMN offered a lower formation temperature for the perovskite phase (700 °C) and a higher relative permittivity than those of precipitated PMN. On sintering at 1150 °C, the maximum relative permittivity observed for the precipitated PMN was 8019 at 1 kHz with a Curie temperature of –11 °C, while that of freeze-dried PMN was 14542 with a Curie temperature of –3 °C at the same frequency.