The color of langatate crystals and its relationship with composition and optical properties
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.
