掺Co钨酸镉单晶体的坩埚下降生长及光谱特性  

Growth of Codoped CdWO_4 Crystals by Bridgman Method and Their Optical Spectra

作　　者：虞灿[1,2] 夏海平[1] 王冬杰[3] 陈红兵[3] 

机构地区：[1]宁波大学光电子功能材料重点实验室 [2]中国人民解放军92746部队 [3]宁波大学材料与化学工程学院

出　　处：《光谱学与光谱分析》2011年第9期2350-2354,共5页Spectroscopy and Spectral Analysis

基　　金：国家自然科学基金项目(50972061);浙江省杰出青年自然科学基金项目(R4100364);宁波市自然科学基金项目(2009A610007;2010A610185);宁波大学王宽诚幸福基金资助

摘　　要：应用坩埚下降法,采用70℃.cm-1的固液界面温度梯度与0.50 mm.h-1生长速度,生长出了初始Co掺杂摩尔百分浓度为0.5 mol%、尺寸为Ф25 mm×120 mm的钨酸镉单晶体。晶体呈透明深蓝色。用XRD表征了获得的晶体。观测到518,564和655 nm三个可见波段吸收带以及发光中心1 863 nm(1 323～2 220 nm)的超宽吸收带。可见波段的吸收归属于Co2+在八面晶格场中4T1(4F)→4A2(4F),4T1(4F)→4T1(4P)跃迁叠加,而红外波段的宽带吸收则为八面体场Co2+的4T1(4F)→4T2(4F)能级跃起所致。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。根据吸收光谱计算出晶格场参数Dq=990 cm-1,Racah参数BC=726.3 cm-1。在520 nm波长光的激发下,观察到778 nm波段的荧光发射,归属于八面体晶格场中Co2+的4T1(4P)→4T1(4F)能级的跃迁。从吸收与荧光强度的变化推断:沿着晶体生长方向,Co2+浓度逐渐增加,有效分凝系数小于1。The CdWO4 crystals with good quality in the size ofφ25 mm× 120 mm, doped with Co in 0. 5% molar fraction in the raw composition, were grown by the Bridgman method by taking -70 ℃· cm ^-1 of solid-liquid interface and -0. 50 mm· h^-1 growth rate. The crystal presents transparence and deep blue. The X-ray diffraction （XRD） was used to characterize the crystals. Three absorption peaks at 518, 564 and 655 nm respectively, which are attributed to the overlapping of 4 T1 （4 F）→4A2 （4F） and 4 T1 （4F）→4 T1 （4p） of Co2＋ octahedrons, and a wide band centered at 1 863 rim, which is attributed to 4 T1 （4F）→4 T2 （4F）, was observed. The absorption results indicated that the Co ions presented ＋2 valence in crystal and located within the distorted oxygen octahedrons. The crystal-field parameter Dq and the Racah parameter B were estimated to be 990 and 726.3 cm^-1 respectively based on the absorption spectra. A fluorescence emission at 778 nm （4T1 （4P）→4T1（4F）） for codoped CdWO4 crystals was observed under excitation by 520 nm light. It can be deduced from the changes in absorption and emission intensity of differ- ent parts of crystal that the concentration of CO2＋ ion in crystal increased along growing direction and the effective distribution coefficient of CO2＋ ion in CdWO4 crystal is less than 1.

关 键 词：Co离子 钨酸镉晶体 坩埚下降法 光谱 

分 类 号：O782[理学—晶体学] P734[天文地球—海洋化学]