Optical spectroscopy methods are used to study the spectra of some oxygen-octahedral ferroelectrics - $LiNbO_3$ and $LiTaO_3$. Study of the role of $BO_6$ octahedron by using spectroscopic methods can cast light on the many physical phenomena that place in $LiNbO_3$ and $LiTaO_3$. For these crystals, absorption edge, band gap, Urbach constants and phonon energy were found.
ÇABUK, S. and MAMEDOV, A. (1998) "A Study of the LiNbO_3 and LiTaO_3 Absorption Edge," Turkish Journal of Physics: Vol. 22: No. 1, Article 5. Available at: https://journals.tubitak.gov.tr/physics/vol22/iss1/5