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.

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Spectral-luminescent properties of Eu 2+ ions in alkaline earth dilithiosilicates of composition MLi 2 SiO 4 (M = Ca, Sr, Ba) have been studied at 77 K. The reasons for the different positions of the Eu 2+ 4f 6 5d → 4f 7 emission band maximum in spectra of MLi 2 SiO 4 were found based on the obtained results. It was shown that the increase in the decay time of the Eu 2+ emission on going from CaLi 2 SiO 4 (0.41 μs) through BaLi 2 SiO 4 (0.64 μs) to Sr-silicate (1.11 μs) correlates with the shift of the emission maximum to longer wavelengths.