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

Gadolinium iron garnet/zirconia (GIG/ZrO2) samples of 1:9 wt. ratio are rea ction sintered at 1300 degreesC 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 hemati te core is a single crystal nearly free of Gd3+. Iron zirconate was found t o precipitate within the hematite core, and it is the same as that first fo und in the aged alpha -Fe2O3-ZrO2 composite. The size of the iron zirconate precipitates decrease from core center toward the edge. The probable proce ss leading to the microstructure and phase changes is discussed. (C) 2001 E lsevier Science B.V. All rights reserved.