Phase evolution during low-temperature synthesis of MgAl2O4

Abstract

Fine magnesium aluminate spinel powder has been synthesized at low temperatures (300–500°C) via thermal decomposition of hydroxide mixtures prepared by coprecipitation from nitrate solutions. The precipitates consisted of simple and mixed magnesium and aluminum hydroxides in crystalline and amorphous states. The effect of heat treatment (100–800°C) on the phase composition of the precipitates was studied. The synthesized fine spinel powder has three levels of structure: spherical conglomerates (1.2–2 μm), ellipsoidal and irregularly shaped agglomerates of medium (300–700 nm) or small (100–150 nm) size, and primary particles (30–60 nm). The size of coherently scattering domains in the powder is 4 ± 1 nm.