Features of Raman Scattering in LiNbO ₃ :Er ³⁺ Crystal With Erbium Gradient

ABSTRACT For the first time, the Raman spectra in a range of 50–2850 cm −1 from different areas of the gradient crystal LiNbO 3 :Er 3+ (congruent in the main components, Er gradient of 0.55 at%/cm) grown by the Czochralski method were investigated. The compositionally homogeneous, nominally pure, congruent LiNbO 3cong ( R = [Li]/[Nb] = 0.946) and the single‐crystal LiNbO 3 :Er 3+ (3.1 wt%), also grown by the Czochralski method, were used as reference samples. It was found that in the gradient crystal LiNbO 3 :Er 3+ (congruent in the main components, Er gradient of 0.55 at%/cm), the intensity of the second‐order Raman lines is significantly higher than the intensity of fundamental vibrations, which is due to the high microheterogeneity of the gradient crystal. A coincidence of the type of Raman spectra in scattering geometries and has been established, for which no explanation has been found at the moment. It has been shown that second‐order Raman spectra can be a powerful tool for studying the compositional and structural perfection of materials based on LiNbO 3 crystals, including doped crystalline and ceramic materials and materials with an artificially specified composition gradient.