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.
出处
《无机材料学报》
SCIE
EI
CAS
CSCD
北大核心
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
关键词
铌酸锂晶体
掺杂
钛
锰
杂质电荷态
点缺陷
LiNbO3:Ti or Mn, heat treatment, impurity charge states, point defects
