Luminescence properties of the Sm-doped borate glasses

The optical absorption and photoluminescence (emission and excitation) spectra as well as decay kinetics of a series of the Sm-doped glasses with Li₂B₄O₇, LiKB₄O₇, CaB₄O₇, and LiCaBO₃ compositions were investigated and analysed. The Li₂B₄O₇:Sm, LiKB₄O₇:Sm, CaB₄O₇:Sm, and LiCaBO₃:Sm glasses of high optical quality have been obtained from the corresponding polycrystalline compounds in the air atmosphere, using a standard glass technology. On the basis of electron paramagnetic resonance (EPR) and optical spectra analysis it was shown that the samarium impurity is incorporated into the glass network as Sm³⁺ (4f⁵, ⁶H_5/2) ions, exclusively. All observed 4f – 4f transitions of the Sm³⁺ centres in the optical absorption and luminescence spectra of the investigated glasses are identified. Most intense emission band of the Sm³⁺ ions peaked about 598 nm (⁴G_5/2 → ⁶H_7/2 transition) is characterised by a single exponential decay with typical lifetime values, which depend on the basic glass composition as well as concentration and local structure of the Sm³⁺ luminescence centres. The quantum efficiency has been evaluated for observed transitions of the Sm³⁺ centres using obtained experimental lifetimes and radiative lifetimes calculated by Judd–Ofelt theory. The calculated high quantum efficiencies and measured quantum yields of luminescence show that the investigated borate glasses are perspective luminescence materials. Energy transfer from the Ce³⁺ non-controlled impurity and intrinsic luminescence centres to the Sm³⁺ centres has been observed. Peculiarities of the Sm³⁺ local structure in the network of investigated glasses have been discussed based on the obtained spectroscopic results and structural data. - Highlights: • The Sm-doped Li₂B₄O₇, LiKB₄O₇, CaB₄O₇, and LiCaBO₃ glasses of high quality were obtained. • EPR, optical absorption and luminescence spectra of Sm³⁺ ions in obtained glasses were studied. • Obtained Sm³⁺ lifetimes in the Li₂B₄O₇, LiKB₄O₇, CaB₄O₇, and LiCaBO₃ glasses were analysed. • The local structure of Sm³⁺ centres in the network of investigated borate glasses is proposed. • The obtained glasses activated with Sm³⁺ are promising luminescent materials in orange–red range