Luminescent properties of Eu2+ and Ce3+ ions in strontium litho-silicate Li2SrSiO4

Abstract

a b s t r a c tThe luminescent properties of Eu 2 + and Ce 3 + ions in Li 2 SrSiO 4 have been studied upon excitation in the 2-20 eV region. Based on the results of luminescent measurements, values of the crystal field splitting and the centroid shift of the Ce 3 + 5d configuration in Li 2 SrSiO 4 were found and compared with those of Ce 3 + ions in some other inorganic compounds. The Eu 2 + ions in Li 2 SrSiO 4 exhibit a broad band emission with a maximum at 576 nm, which is due to the 4f 6 5d-4f 7 transition. It was shown that the long-wavelength position of the Eu 2 + emission in Li 2 SrSiO 4 is caused by the large crystal-field splitting of the Eu 2 + 4f 6 5d configuration and relatively high degree of covalency of the Eu-O bond. The stabilization of Eu 2 + ions in Li 2 SrSiO 4 during the synthesis process requires a strong reducing agent. Two phenomenological approaches to explain the low stability of Eu 2 + in Li 2 SrSiO 4 are also discussed.

Luminescence of Eu2+ ions in alkaline earth dilithiosilicates

“…Because the luminescence excitation spectrum of Ce 3+ in this compound exhibits a similar band, it can be assigned to absorption of excitation energy by the BaLi 2 SiO 4 crystal lattice. In this instance it can be concluded that the optical absorption edge for BaLi 2 SiO 4 was shifted to lower energies compared with CaLi 2 SiO 4 (7.15 eV at 10 K [15]) and SrLi 2 SiO 4 (6.85 eV at 10 K [8]). The observed shift may be due to involvement of AE states (Ba 6s) in electronic transitions near the BaLi 2 SiO 4 fundamental absorption edge.…”

“…It can be concluded that stabilization of Eu 2+ in MLi 2 SiO 4 requires the use of a reducing agent in the synthesis. at 525 nm [8]. The luminescence excitation spectrum of Eu 2+ in BaLi 2 SiO 4 was different.…”

“…Experimental. The compound SrLi 2 SiO 4 :Eu 2+ has been studied previously [8]. Therefore, the present work fo- To whom correspondence should be addressed.…”

“…The spectral and luminescent properties of SrLi 2 SiO 4 :Eu 2+ are the most fully studied of this group of compounds. In particular, it was shown [8] that the significant shift to long wavelengths of the luminescence maximum of Eu 2+ in SrLi 2 SiO 4 (λ max = 576 nm) compared with that of most AE oxides (λ max = 370-480 nm [1]) was determined by two factors. These were the significant splitting of the Eu 2+ 4f 6 5d configuration by the crystal field and the relatively high covalency of the metal-oxygen bond.…”

“…Samples were prepared as pressed KBr pellets. The equipment and procedure for the luminescence measurements were analogous to those described previously [8].…”