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, 6H5/2) 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 (4G5/2 → 6H7/2 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.