摘要
采用高温固相反应合成了 (La1-xEux) (BO2 ) 3 ,利用X射线粉末衍射方法确定其晶体结构 ,利用红外光谱探讨了 [BO3 ]单元的聚合情况。根据 (La1-xEux) (BO2 ) 3 所属空间群中等效点系的对称性分析及Eu3 + 的荧光光谱 ,详细地探讨了Eu3 + 的发光性质与其所处格位点对称性的关系。La(BO2 ) 3 ∶Eu3 + 体系中 ,Eu3 + 出现较强的5D0 →7F1磁偶极跃迁 ,因而Eu3 + 主要占据点对称性为Ci 的格位 ,出现的其它跃迁是部分Eu3 + 占据偏离Ci 的格位 ,而并非占据C2 或C1格位 ,另外 ,5D0 →7F4 跃迁发射很强 ,其原因尚不清楚。选择适当的助熔剂可以提高样品的结晶程度 ,有利于Eu3 + 占据严格的Ci 格位 ,增强材料的发光性能。
In many hosts, Eu 3+ can be a fluorescent probe to detect local symmetry and microstructure of rare earth ions in a crystal. (La 1-x Eu x)(BO 2) 3 has been synthesized by solid state reaction at high temperature, and this paper is to establish the relationship between the spectra of Eu 3+ and the crystal structure of (La 1-x Eu x)(BO 2) 3. The polycondensation of [BO 3] units has been analyzed from infrared spectra, and the results suggests the negative ion units are polymerized into chain structure such as (BO 2) n n- , among which La 3+ and Eu 3+ are scattered. The crystal structure has been investigated using X ray powder diffraction, which indicates the sample is monoclinic, with space group being I2/a. According to the crystal structure and emission spectra of La(BO 2) 3∶Eu 3+ , the relationship between the luminescent properties and the site symmetry of Eu 3+ in La(BO 2) 3 has been discussed in detail. For space group I2/a, the symmetrically equivalent points of 4a, 4b, 4c and 4d positions have inverse centers, so their site symmetry is C i,but there is no inverse center for 4e and 8f position,and their site symmetries are C 1 and C 2 respectively. In La(BO 2) 3∶Eu 3+ system, 5D 0→ 7F 0 transition does not exist, moreover, the emission corresponding to 5D 0→ 7F 1 transition is much more intense than that of 5D 0→ 7F 2 transition, so the Eu 3+ must be located at the site of C i symmetry, and the 5D 0→ 7F 2, 7F 3 and 7F 4 transitions are attributed to a little part of Eu 3+ deviated from inverse centers. In addition, it has been confirmed that adding a certain flux may be of great advantage for the sample to be well crystallized and for Eu 3+ to be located at a site of perfect C i symmetry so that 590nm emission corresponding to 5D 0→ 7F 1 transition is greatly intensified. On the other hand, the reason that Eu 3+ gives very intense emission nearby 697nm corresponding to 5D 0→ 7F 4 transition need to be further investigated.
出处
《发光学报》
EI
CAS
CSCD
北大核心
2000年第3期210-213,共4页
Chinese Journal of Luminescence
基金
国家自然科学基金资助!( 4 9770 99)
