Co^(2+)∶LiNbO_3晶体的坩埚下降法生长及其光谱性质

Co^(2+)-Doped LiNbO_3 Crystals Grown by the Bridgman Method and Their Optical Spectra

应用坩埚下降法,以同成分化学摩尔分数比(Li2O:48.6%,Nb2O5:51.4%)为原料,以CoO作为掺杂物,在合适的温度梯度(20~40℃/cm)与生长速度(1~3mm/h),生长出了Co2+掺杂摩尔分数分别为0.1%与0.3%的LiNbO3(LN)晶体。用X射线衍射(XRD)与差热分析(DTA)表征了获得的晶体。测定了不同部位晶体从350~2500nm的吸收光谱。观测到520nm,549nm与612nm三个分裂的尖吸收峰以及以1358nm为发光中心的吸收带。从吸收特性表明,Co离子掺杂于畸变的氧八面体中,呈现+2价态,并且沿着晶体生长方向浓度逐渐减少,Co2+在LiNbO3晶体中的有效分凝系数大于1。研究了不同部位晶体在900nm以下的荧光光谱特性,在750nm发现有较强的荧光发射,并随着激发波长的增长,荧光发生红移。

The growth of LiNbO3 (LN) crystals doped with Co2+ ions in 0.1 and 0.3 mol% concentrations by the Bridgman method in congruent composition (Li2O: 48.6mol%, Nb2O5: 51.4 mol%) and CoO as dopant under the conditions of temperature gradient around 20-40 °C/cm for solid-liquid interface and growth rate of 1-3 mm/h was reported. The X-ray diffraction (XRD) and differential thermal analysis (DTA) were used to characterize the crystals. The absorption spectra of different parts of crystals from 350 to 2500 nm were recorded. The three split absorption peaks at 520, 549 and 612 nm, and a wide band centered at 1358 nm were observed. The absorption results indicated that the Co ions presented +2 valence in crystal and located within the distorted oxygen octahedrons. The concentration of Co2+ ion in crystal reduced along growing direction, and the effective distribution coefficient of Co2+ in LiNbO3 crystal was more than 1. The emission spectra under 900-nm wavelength were studied. The band at 750 nm was observed and the peak was red-shifted as the increase of exciting wavelength.