Terbium–yttrium–iron garnet revisited

An investigation was made into the synthesis and magnetic properties of Tb(3 − x)YxFe5O12 garnet ferrite synthesized by coprecipitation from hydrated chlorides of rare-earth elements and ferrous sulfate. The mixed hydroxide coprecipitate was calcined at 1000 °C. Ring-shaped compacts were obtained by dry pressing of finely milled calcined coprecipitate powder to which an aqueous solution containing 15 wt% of PVA was added. The compacts were dried and sintered in a 1250–1450 °C temperature range. The main conclusions of this study were that saturation magnetization in TbYIG depended strongly on the sintering temperature; and the best result among tested compositions occurred for Tb2.4Y0.6Fe5O12 after sintering at 1400 °C. The trend of TbYIG to degrade at sintering temperatures above 1400 °C was evidenced. The grain size increased along with the sintering temperature, while the coercive force reached a minimum value, increasing afterwards. This non-linear temperature dependence reflected what was predicted by the phase diagrams of the Tb–Y–Fe–O system at elevated temperatures.