We discuss the main reasons for the appearance of low-intensity 'extra' lines (not corresponding to fundamental lattice vibrations) in the Raman spectrum of nonstoichiometric nonlinear optical LiNbO₃ crystals. These lines arise due to the formation of two-particle states of acoustic crystal vibrations with a zero total wave vector, strong anharmonicity of fundamental vibrations, the presence of microstructures (clusters) whose structure differs from that of the crystal matrix, the presence of microinclusions of impurity phases of other lithium niobates, and the photorefraction effect. It is shown that 'extra' Raman spectral lines can serve as a new highly sensitive tool for studying the structural perfection of LiNbO₃ crystals.

Typically, an English full text is available in about 1 month from the date of publication of the original article.

Correspondence should be addressed to † n.sidorov@ksc.ru, ‡ n.tepliakova@ksc.ru, and § m.palatnikov@ksc.ru Keywords: lithium niobate, single crystals, Raman spectroscopy, defects, 'extra' lines, laser conoscopy, photoinduced light scattering PACS: 33.20.Fb, 42.70.−a, 42.70.Mp, 61.72.−y (all) DOI: 10.3367/UFNe.2024.11.039806 URL: https://ufn.ru/en/articles/2025/3/c/ Citation: Sidorov N V, Teplyakova N A, Palatnikov M N "Manifestation of defects and imperfections of lithium niobate crystals in Raman spectra" Phys. Usp. 68 (3) (2025) Received: 19th, March 2024, revised: 20th, June 2024, accepted: 13th, November 2024 Оригинал: Сидоров Н В, Теплякова Н А, Палатников М Н «Проявление дефектов и несовершенств кристаллов ниобата лития в спектрах комбинационного рассеяния света» УФН 195 260–275 (2025); DOI: 10.3367/UFNr.2024.11.039806