G. M. Kuz’micheva, I. A. Kaurova, V. B. Rybakov, S. S. Khasanov, A. Cousson,O. Zaharko, E. N. Domoroschina, and A. B. Dubovsky
Langatate crystals grown by the Czochralski method in <0001> and <0111> directions both without subsequent annealing (from colorless to orange crystals) and with vacuum (colorless and pale-green crystals) and air (orange crystal) annealing have been investigated by neutron diffraction, X-ray diffraction and optical spectroscopy. The main types of point defects were compared with absorption bands: oxygen vacancies - VO(0.35-0.36 μm), the vacancies in the lanthanum position - VLa''' (0.29-0.30 μm); the absorption band at 0.48-0.49 μm is typical for the colored samples. The relationship between the X color coordinate (red component) and the oxygen contents has been obtained. The green color of the sample annealed in vacuum is due to the presence of Ta+3 ions in the La(Ta3+,Ga)O3 phase that has the structural and geometric agreement with langatate structure.