Luminescence properties of the Sm-doped borate glasses

Abstract

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 598nm (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.