Sidorov Nikolay V, Bobreva Lyubov A, Pyatyshev Alexander Yu, Palatnikov Mikhail N, Palatnikova Olga V, Skrabatun Alexander V, Teslenko Andrei A, Tarabrin Mikhail K
Tananaev Institute of Chemistry-Subdivision of the Federal Research Centre, Kola Science Centre of the Russian Academy of Sciences (ICT RAS), 184209 Apatity, Murmansk Region, Russia.
P. N. Lebedev Physical Institute of the Russian Academy of Sciences, 119991 Moscow, Russia.
Materials (Basel). 2025 Jul 8;18(14):3218. doi: 10.3390/ma18143218.
LiTaO crystals doped with Cr and Nd ions are promising for developing active nonlinear laser media. In this work, the defect structure of LiTaO crystals, including those doped with Cr and Nd, is examined. X-ray patterns of all six investigated LiTaO:Cr:Nd crystals are identical and correspond to a highly perfect structure. Using optical microscopy, the presence of defects of various shapes, microinhomogeneities, and lacunae was revealed. The optical absorption and Raman scattering spectra of a series of nonlinear, optical, double-doped LiTaO:Cr:Nd (0.06 ≤ [Cr] ≤ 0.2; 0.2 ≤ [Nd] ≤ 0.45 wt%) crystals showed that at concentrations of doping Cr ions less than 0.09 wt% and Nd ions less than 0.25 wt%, the crystal structure is characterized by a low level of defects, and the optical transmission spectra characterized by narrow lines corresponding to electron transitions in Nd ions. In this case, for the radiative transition in the cation sublattice, the existence of three nonequivalent neodymium centers is observed, and for the radiative transition, two nonequivalent centers are observed. IR absorption spectroscopy in the OH-stretching vibration range revealed two main spectral regions: 3463-3465 cm, associated with stoichiometry changes, and 3486-3490 cm, linked to complex defects such as (V)-OH and (Ta)-OH. A distinct low-intensity line at ~3504 cm was observed only in doped crystals, attributed to (Nd)-OH defects that significantly distort the oxygen-octahedral clusters due to the larger ionic radius of Nd compared to Ta. In contrast, Cr-related defects cause only minor distortions. The Klauer method indicated that the highest concentration of OH-groups occurs in the LiTaO:Cr (0.09 wt%):Nd (0.25 wt%) crystal, where multiple complex defects are present.
掺杂铬和钕离子的钽酸锂晶体有望用于开发有源非线性激光介质。在这项工作中，研究了钽酸锂晶体（包括掺杂铬和钕的晶体）的缺陷结构。所有六种研究的钽酸锂：铬：钕晶体的X射线图谱相同，对应于高度完美的结构。使用光学显微镜，发现了各种形状的缺陷、微观不均匀性和空隙。一系列非线性光学双掺杂钽酸锂：铬：钕（0.06≤[Cr]≤0.2；0.2≤[Nd]≤0.45 wt%）晶体的光吸收和拉曼散射光谱表明，当铬离子掺杂浓度小于0.09 wt%且钕离子掺杂浓度小于0.25 wt%时，晶体结构的缺陷水平较低，光透射光谱的特征是对应于钕离子中电子跃迁的窄线。在这种情况下，对于阳离子亚晶格中的辐射跃迁，观察到三个不等价的钕中心，对于辐射跃迁，观察到两个不等价的中心。在OH伸缩振动范围内的红外吸收光谱揭示了两个主要光谱区域：3463 - 3465 cm，与化学计量变化相关；3486 - 3490 cm，与诸如（V）-OH和（Ta）-OH等复杂缺陷相关。仅在掺杂晶体中观察到约3504 cm处明显的低强度线，这归因于（Nd）-OH缺陷，由于钕的离子半径比钽大，该缺陷会显著扭曲氧八面体簇。相比之下，与铬相关的缺陷仅引起轻微扭曲。克劳尔方法表明，OH基团的最高浓度出现在存在多个复杂缺陷的钽酸锂：铬（0.09 wt%）：钕（0.25 wt%）晶体中。
