DISTORTED KOSSEL DIFFRACTION OF LiNbO₃ IN THE VICINITY OF 75°C

Some abnormal Kossel lines of pure LiNbO₃ crystal have been observed in the vicinity of 75°C and in Ti-diffused one at wide temperature range. Reasonable explanation is that the diffraction plane inclines locally from its normal position at that temperature. A computer simulation has been made and shows an agreement with the calculations. The change of elastic constant or heat expansion coefficient etc. may be the cause of the deformation of the pure crystal near 75°C.