Ce3+离子激活的SrB4O7的VUV光谱

Ce³⁺只有一个4f电子,具有最简单的4f¹5d⁰基态结构,其激发光谱直接反映了5d轨道的能量状态。由于同一基质晶格相同格位上不同稀土离子受基质晶体场影响相近,所以根据Ce³⁺离子的光谱可以推测和分析其他稀土离子的5d轨道能量,是研究其他稀土离子f-d跃迁的基础。采用高温固相法合成了Ce³⁺离子激活的SrB₄O₇发光体,测定了样品在130~350nm波长范围的激发光谱和相应的发射光谱。指认了VUV激发光谱上Ce³⁺离子的5个4f¹→4f⁰5d¹跃迁激发带,讨论了SrB₄O₇的基质吸收带和Ce³⁺的5d轨道在SrB₄O₇中的晶体场劈裂、5d轨道能级重心及SrB₄O₇:Ce³⁺的发射光谱和Stokes位移。

VUV Spectrum of Ce3+ Activated SrB4O7

The ground state of Ce³⁺ is 4f¹5d⁰,which have only one 4f electron on the configuration.For this reason,the excitation spectrum of Ce³⁺ ion directly shows the energy state of 5d level.Ce³⁺ ion can be used as a probe to investigate the f-d transitions of other rare-earth ions in same host lattice sites,since the similarity of the crystal-field effect on the 5d states of different rare earth ions in the sites.The phosphor,Ce³⁺ ion activated tetra-borate SrB₄O₇,was prepared by high temperature solidstate reaction technique in present paper.Na⁺ ion was added to balance the electronic charge due to the different electronic charge value between Ce³⁺ and Sr²⁺ ions.The XRDpatterns of the sample Sr_0.96Ce_0.02Na_0.02B₄O₇ are in good line with the JCPDS standard card 15-801(SrB₄O₇).The VUV(vacuum ultraviolet) excitation and emission spectra were measured at the VUVspectroscopy experimental station on beam line 3B1B,Beijing Synchrotron Radiation Facilities(BSRF),under normal operating conditions(2.2 GeV,100 mA) at 293 K.The spectroscopic properties of this phosphor are investigated in the wavelength region 130~400 nm.The host-related Absorption is found to be about 155 nm.The five bands corresponding to the 4f¹→4f⁰5d¹ transitions of Ce³⁺ ions are identified as 277,242,228,217 and 202 nm in the host lattices.Therefore,the 5d crystal field splitting and the barycenter of Ce³⁺ in the host lattice are calculated to be 13.4×10³ and 43.4×10³cm^-1,respectively.The doublet emission bands of Ce³⁺ in the host lattice are observed at 293 and 313 nm.Hence,the Stokes shift is 1971cm^-1.Because SrB₄O₇ and SrBPO₅ share iso-structural characteristics: the cations are same,and all of anions are tetrahedral AO₄(A=B,P).The spectroscopic properties of Ce³⁺ in these host lattices are compared and discussed qualitatively.