Combustion synthesis and properties of Ln 3Fe 5O 12 and yttrium aluminium garnets

Abstract

The rare earth iron garnets Ln 3Fe 5O 12 and Y 3Al x Fe 5− x O 12, where x = 1.0−5.0, and Y 1.5Gd 1.5Al 0.2Fe 4.8O 12 have been prepared by the combustion of redox mixtures containing corresponding metal nitrates and oxalyl dihydrazide, i.e. C 2H 6N 4O 2 at 350 °C. The solid combustion products are amorphous, submicrometre-sized powders which, on heating at 750 °C for 3 h, yield crystalline single-phase garnets. The particle size of the garnets is below 1 μm and the surface area ranges from 16 to 90 m 2 g −1. Yttrium iron garnet could be sintered to a density of more than 95% at 1200 °C for 3 h, giving an average grain size of 3–5 μm.