Spectroscopy of the CaB4O7 and LiCaBO3 glasses, doped with terbium and dysprosium

Abstract

A series of borate glasses of high optical quality with CaB4O7:Tb, LiCaBO3:Tb, CaB4O7:Dy, and LiCaBO3:Dy compositions containing 0.5 and 1.0mol% Tb2O3 and Dy2O3 impurity compounds were obtained from corresponding polycrystalline compounds using standard glass technology. By electron paramagnetic resonance (EPR) and optical spectroscopy it was shown that the Tb and Dy impurities are incorporated as Tb3+ (4f8, 7F6) and Dy3+ (4f9, 6H15/2) ions in the Ca and Li(Ca) sites of CaB4O7 and LiCaBO3 glasses network, respectively. The luminescence excitation and emission spectra as well as luminescence kinetics of the Tb3+ and Dy3+ centres in the CaB4O7 and LiCaBO3 glasses have been investigated and analysed in comparison with obtained earlier results for Tb3+ and Dy3+ centres in the Li2B4O7 glasses. All observed f–f transitions of the Tb3+ and Dy3+ centres in the luminescence excitation and emission spectra have been identified. Luminescence kinetics show single exponential decay for Tb3+ and Dy3+ centres in the CaB4O7 and LiCaBO3 glass network. The lifetime values for the main emitting levels of the Tb3+ and Dy3+ centres in all investigated glasses were determined at room temperature and their dependencies on the basic glass compositions and impurity concentrations are discussed. The obtained results show that the CaB4O7 and LiCaBO3 glasses are promising luminescent materials, operating in green and yellow–blue spectral regions, when activated with Tb3+ and Dy3+ ions, respectively.