Chemically Induced Grain Boundary Migration of MgAl2O4 by ZnO

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J. Korean Ceram. Soc. > Volume 29(11); 1992 > Article

Journal of the Korean Ceramic Society 1992;29(11): 888.

ZnO의 화학구동력에 의한 $MgAl_2O_4$의 입계이동

최균, 조의성, 강석중

한국과학기술원 무기재료공학과

Chemically Induced Grain Boundary Migration of MgAl2O4 by ZnO

ABSTRACT

The chemically induced grain-boundary migration has been studied in MgAl2O4 spinel under ZnO atmosphere. MgAl2O4 compacts been prepared by sintering powder mixture of Al2O3 and MgO at 1$600^{circ}C$ for 60 h in air. The sintered MgAl2O4 has been heat-treated at 150$0^{circ}C$ in a ZnO atmosphere. During the heat-treatment grain boundaries have become curved or faceted, and the total area of grain boundaries have increased. In the migrated region, the ZnO content is higher by 6 wt% than that in other regions, indicating that the migration was induced by addition of ZnO. In some shrinking grains, the faceted planes of different grain boundaries for the same grain are parallel to each other. This result provide an experimental support for the coherency strain energy in diffusion layer of the shrinking grain as being the major driving force. Calculated coherency strain energy of MgAl2O4 shows the maximum at {111} planes and the minimum at {100} planes. Although the minimum surface energy is at {111} planes, the faceted moving boundaries are expected to be {100} planes because of lowest driving force for the grain-boundary migration.