纯铌酸锂晶体红外光谱的低温研究

Study on infrared absorption spectra of congruent lithium niobate crystals at low temperature

测量了同成分纯铌酸锂的低温红外光谱,发现低温下铌酸锂晶体将会出现位于3200 cm-1左右的新红外吸收峰.研究发现该峰与晶体中的氢离子无关,并且其峰强和峰形都随温度的升高发生复杂的变化.基于上述实验结果,认为该峰应该起源于电子在相邻的小极化子(Nb4Li+)和自由极化子(Nb4N b+)之间的跃迁.另外,通过拟合发现新红外吸收峰可分解成三个高斯峰,这三峰应归因于能量有细微差别的三种跃迁.

Infrared absorption spectra of congruent lithium niobate crystals are measured at low temperature, and a new peak is found at 3200 cm^-1 in the spectra. Results show that this peak has no relationship with hydrogen in the crystals, and that with the increase of the temperature, both the intensity and shape of the peak change in a complex way. Based on these results, we suggest that the new peak results from the electron transfer from small polarons （NbLi^4＋ ） to free polarons （NbNb^5＋）. In addition, we find that this peak can be decomposed into three Gauss peaks, and the three components are attributed to three transfer processes with different energies.