As-grown single crystals, grown from the Fe–Ni–C system under high temperatures and high pressures, were examined by means of transmission electron microscopy. Prismatic dislocation loops and concentric dislocation loops existed in the diamond, which were related to the non-equilibrium nature of the synthesis process. Prismatic dislocation loops could be formed by vacancy condensation during rapid cooling from high temperatures, and the Burgers vector of the dislocation was determined, by diffraction contrast, to be ½<110>. Moiré fringes formed by 2 overlapping (111) close-packed planes were used to study concentric dislocation loops. The concentric loops could arise from thermal stresses caused by inclusions in the diamond; which set up a strain field due to the thermal contraction difference between the inclusions and the diamond during cooling from high temperatures.

Prismatic Dislocation Loops and Concentric Dislocation Loops in HPHT-Grown Diamond Single Crystals. L.W.Yin, M.S.Li, Z.D.Zou, Z.G.Gong, Z.Y.Hao: Materials Science and Engineering A, 2003, 343[1-2], 158-62