Slip systems in gadolinium gallium garnet single crystals

Gd₃Ga₅O₁₂ single crystals with compression axes of different orientations have been deformed under creep conditions in air at 1450° C and 1550° C (0.86 T_M and 0.92 T_M, respectively, where T_M is the melting temperature). After a few per cent of permanent strain the deformation substructure has been studied by optical and transmission electron microscopy. Etching and bi-refringence patterns indicate that slip on {110}, {112} and {123} can be activated depending on the orientation of the compression load. Dislocations with a/2 111 Burgers vectors have been observed to glide in {110 planes. They exhibit a segmented aspect suggesting their dissociation out of the glide plane.