不同热化学还原LiNbO_3：Ti或Mn晶体杂质电荷态和点缺陷  

Impurity Charge States and Point Defects in LiNbO_3:Ti or Mn Crystals Treated by Defferent Thermo-Chemical Reductions

作　　者：刘建成[1] 唐连安[1] 谭浩然[1] 石春山[1] 

机构地区：[1]中国科学院上海硅酸盐研究所,中国科学院长春应用化学研究所稀土化学与物理开放实验室

出　　处：《无机材料学报》1994年第4期391-398,共8页Journal of Inorganic Materials

基　　金：稀土化学与物理开放实验室资助

摘　　要：采用光学吸收和电子顺磁共振（ＥＳＲ）技术表征不同热化学还原ＬＩＮｂＯ３：Ｔｉ，Ｍｌｉ（ＬＮ：Ｔｉ，Ｍｎ）和纯的Ｌｉ／Ｎｂ＝０．９４５一致熔化ＬｉＮｂＯ３（ＬＮ）晶体的热力学还原习性．将ＬＮ：Ｔｉ（厚度为１ｍｍ）样品放在Ｌｉ２ＣＯ３中、６００℃、保温７ｈ，产生６９０ｕｒｎ（～１．８ｅＶ，Ｔ＝６７％）和峰值靠近７８５ｎｍ（Ｔ＝７１％）的７７０￣８１０ｎｍ光学吸收带，它们分别对应于Ｔｉ（３＋）的２Ｔ→２Ｅ跃迁以及室温稳定Ｆ＋心滞有一个电子的氧空位）．经真空１．２Ｐａ，８００℃２ｈ还原后，存在峰值为６７５ｎｍ（Ｔ＝５２％）的４８０～７８０ｎｍ平滑吸收带，它们是Ｔｉ（３＋）、Ｆ心和Ｆ＋心重叠吸收，但是，在Ａｒ气氛下、９００℃、８ｈ处理后，仅能看到峰值在６７５ｎｍ（Ｔ＝５２％）的６００～７８０ｎｍＴｉ（３＋）的弱吸收．来自未处理ＬＮ：Ｔｉ晶体的室温和Ｘ带的ＥＳＲ＄观察到ｇ＝４．３４８，共振磁场０．１５２ＴＨ（ｐ－ｐ）＝０．０１６３Ｔ微波吸收峰，以及四组精细结构Ｂ线（每一ｆｓ线是由６条超精细结构ｈｆｓ组成），ｇ值从３．４６０～１．６７９吸收，它们分别归为于晶体杂质Ｆｅ（３＋）和Ｍｎ（２＋）离子．真空还原后，Ｆｅ（３＋）的?Optical absorption, electron spin resonance (ESR) techniques were used to characterize the thermodynamical reduction behaviour in LiNbO3:Ti, Mn (LN:Ti, Mn) and pure LiNbO3 (LN) with congruent ratio Li/Nb=0.945 crystals treated by different thermo-chemical reduction. It was shown that under heating LN:Ti (thickness 1mm) up to 600'C in Li2CO3 for 7h, an optical absorption band at 690nm (1.8eV T=67%) and 770￣810nm peaked near 785nm (T=71%), which correspond to the 2T→2E transition of Ti(3+) and F+ center (oxygen vacancy with 1 electron), stable at room temperature respectively,are generated. Then after reduction for Zh at 800℃ in vacuum of 1.2Pa there was a 480￣780nm smooth absorption band peaked at 675urn (T=52%) correspponding to three kinds of Ti(3+), F Center and F+center overlap absorption, but for 8h at 900℃ under Ar gas, one can see only a 600￣780nm weak absorption peaked at 675urn (T=52%) due to Ti(3+). A microwavelength absorption peak at g=4.348 with resonance magnetic field 0.1250T and H(p-p)=0.0163T, and four fs lines with sts hfs lines eacn ac for g from 3.460 to 1.679 were observed by ESR spectrum arising from the untrested LN:Ti crystal at room temperature and X band, which may assigned to Fe(3+) and Mn(2+) ions as impurities in the crystal, respectively. After reduction in vacuum, ESR line for Fe(3+) disappeared, but Mn(2+) still occurred. Because the ESR measurement was carried out at room temperature, one can not see Ti(3+) single fs line.LN:Mn crystal as grown in air contain both Mn(3+) and Mn(2+), since heating reduction in Li2CO3made Mn(3+) into Mn(2+), changing the crystal colour from green (Mn(3+)) to yellow (Mn(2+)). Mn(2+) ions was confirmed by ESR spectra arising from samples of crystal head powder with yellow colour and crystal tail powders with green-brown colour. To facilitate comparisons, three kinds of reduction treatments were performed for undoped congruent LN sample, and their transmission spectra were also measured and anslysed.

关 键 词：铌酸锂晶体 掺杂 钛 锰 杂质电荷态 点缺陷 

分 类 号：O614.111[理学—无机化学]