化学计量比LiNbO_3晶体的激光显微拉曼光谱研究

Study on laser-micro-Raman spectra in near-stoichiometric LiNbO_3 crystals

对用助熔剂提拉法生长的近化学计量比LiNbO3晶体进行了激光显微拉曼光谱测试分析 ,与同成分LiNbO3晶体相比较 ,A1 (TO)与E(TO)模的谱线数目、频率基本不变 ,验证了LiNbO3晶体属置换式固溶体的结论 .738cm- 1 处拉曼振动峰 (A1 (LO)模 )的相对强度随晶体中Li2 O含量的增加发生了明显的变化 ,在两种掺杂晶体中 ,此振动峰已经消失 .根据Li空位模型 ,从占位和结构上进行了分析讨论 .在 15 2和 872cm- 1 处拉曼振动峰半高宽随晶体中Li Nb的增大而变窄 ,对二者关系进行了线性拟合 ,利用拟合公式可根据拉曼振动峰半高宽计算晶体中的Li Nb值 .

The laser-micro-Raman spectra of near-stoichiometric LiNbO 3 crystals were measured and analyzed. The crystals were grown by flux pulling method. Compared with the congruent LiNbO 3 crystal, the number and frequency of Raman spectral lines of A 1(TO) and E(TO) modes have no change. It was validated that the LiNbO 3 crystal is substitutional solid solution. The relative intensity of 738cm -1 Raman peak(A 1(LO)) exhibited obvious change when the Li 2O contents increase in pure LiNbO 3 crystal, the 738cm -1 Raman peak disappeared in the Mg-doped and Zn-doped LiNbO 3 crystals. These Raman peaks were discussed and explained from the occupied site and structure according to the Li vacancy model. The full width at half maximum (FWHM) of the 152 and 872cm -1 Raman peaks narrows with increasing the Li/Nb in the crystals. Their relationships were fitted linearlly, using the fitting equation, and the Li/Nb ratio can be calculated according to the FWHM of Raman peaks.