X‐ray diffraction, infrared, and Raman spectra of Nd‐doped LiTaO3(LT:Nd) were examined. X‐ray diffraction patterns of thexandyfaces display the appearance of new diffraction peaks and the existence of microtwin crystals, indicating the microstructural deviation from a trigonal system of pure LT crystal. Infrared transmission spectrum shows more than seven strong vibrational bands in the high frequency region 1500–6000 cm−1. Their intensities and frequencies hardly change after annealing the sample at high temperature. We attribute these bands to the existence of defects and some metal and organic complexes in the sample. Similar results were obtained from the Raman spectra. In addition, the transmitted polarized light photomicrograph of theZface of LT:Nd displays the occurrence of a helix dislocation. All experimental results indicate that the microstructural imperfection of LT:Nd can lead to some new optical effects. ©1995 American Institute of Physics.