COMBUSTION SYNTHESIS AND PROPERTIES OF LN3FE5O12 AND YTTRIUM ALUMINUMGARNETS

The rare earth iron garnets Ln3Fe5O12 and Y3AlxFe5-xO12, where x=1.0-5 .0, and Y1.5Gd1.5Al0.2Fe4.8O12 have been prepared by the combustion of redox mixtures containing corresponding metal nitrates and oxalyl dih ydrazide, i.e. C2H6N4O2 at 350-degrees-C. The solid combustion product s are amorphous, submicrometre-sized powders which, on heating at 750- degrees-C for 3 h, yield crystalline single-phase garnets. The particl e size of the garnets is below 1 mum and the surface area ranges from 16 to 90 m2 g-1. Yttrium iron garnet could be sintered to a density of more than 95% at 1200-degrees-C for 3 h, giving an average grain size of 3-5 mum.