Dislocations in gadolinium gallium garnet (Gd₃Ga₅O₁₂)-I. Dislocations at inclusions

Dislocations near inclusions in gadolinium gallium garnet crystals have been examined by optical microscopy. The inclusions were 5-200 μm in diameter and were compressed by the matrix. Dislocations were detected by means of the optical birefringence they induced or from the etch pits formed where they met the sample surface. The dislocations were loops 0.01-0.5 mm in diameter which encircled the inclusions and lay on {111}, {110} and {100}. The Burgers vectors of the loops were perpendicular to their plane. Loops were formed by climb and were of the interstitial variety. Mechanisms for the formation of interstitial loops at inclusions compressed by the matrix are described. © 1973.