Phase transformation in reaction-sintered Gd3Fe5O12–ZrO2 (II)

Gadolinium iron garnet/zirconia (GIG/ZrO2) samples of 1:9 wt. ratio are reaction sintered at 1300°C for 8 h and studied by analytical electron microscopy. The GIG grain was found to transform into a Zr4+-doped hematite core surrounded by Gd-stabilized cubic-ZrO2 polycrystals shell. The hematite core is a single crystal nearly free of Gd3+. Iron zirconate was found to precipitate within the hematite core, and it is the same as that first found in the aged α-Fe2O3–ZrO2 composite. The size of the iron zirconate precipitates decrease from core center toward the edge. The probable process leading to the microstructure and phase changes is discussed.