Hydrothermal Preparation of Ultrafine Ferrites and Their Sintering

Abstract

Ultrafine and nearly spherical ferrites such as NiFe 2 O 4 , ZnFe 2 O 4 , Ni x Zn 1−x Fe 2 O 4 , Mn 0.5 Zn 0.5 Fe 2 O 4 , and CoFe 2 O 4 were prepared under mild hydrothermal conditions by precipitating from metal nitrates with aqueous ammonia. These hydrothermal ferrite powders were shown to sinter to almost theoretical density at 1000°C without any sintering aids.