Growth Ridges, Etched Hillocks, and Crystal Structure of Lithium Niobate

Growth feature of a LiNbO 3 crystal obtained by the pulling method has been studied. The formation of growth ridges was interpreted as the intermittent growth of the form {102̄}, which was the most readily grown form from the melt. The point group of the high temperature, paraelectric phase was uniquely determined as 3̄2/ m from the symmetry elements of the configuration of ridges. On (001̄) planes, the triangular etched hillocks were observed. Orientations of the hillocks on the antiparallel domains were related by 2-fold rotation axis parallel to [100] consistent with the phase transition of the type 3̄2/ m →3 m . The atomic arrangement in the form {102̄} was examined, and a three-dimensional framework of the corner-shared Nb-O octahedra, similar to the one in perovskite, was found.