Luminescence and vacuum ultraviolet excitation spectroscopy of samarium doped SrB4O7

Sm²⁺ and Sm³⁺ co-doped SrB₄O₇ could be utilized in several high-level optical devices and fundamental knowledge about the optical behavior of these materials benefits the development of luminescent applications. Herein, we report luminescence and its vacuum ultraviolet (VUV) excitation spectra in samarium doped SrB₄O₇. Both, Sm²⁺ and Sm³⁺ luminescence centers have been examined and distinguished in the emission and the excitation spectra investigated under synchrotron radiation. The contribution of either Sm²⁺ or Sm³⁺ emission lines into the emission spectra heavily depended on the excitation energy, and strong f-f transitions of both Sm²⁺ and Sm³⁺ were detected. At 10 K, a broad intrinsic luminescence in the UV range was detected and attributed to the radiative transition of either bound or self-trapped exciton in SrB₄O₇. The optical behavior, including e.g. inter-configurational f-d transitions of Sm⁽ⁿ⁺⁾ were elucidated with first-principles calculations. Partial density of states well represents the changes of the electronic states that are related to the samarium doping, which in turn explains the emerging features in excitation spectra. In summary, the obtained results clarify the excitation and emission behavior of samarium doped SrB₄O₇.