Vol. 40, Issue 2, pp. 413-426 (2010)

Abstract

A series of Eu- and Pr-doped glasses with SrO–2B₂O₃ (or SrB₄O₇) composition were obtained and their spectroscopic properties were investigated. The SrB₄O₇ polycrystalline compounds were synthesised at T = 1300 K using high purity strontium carbonate (SrCO₃) and boric acid (H₃BO₃). The Eu and Pr impurities were added to SrB₄O₇ compounds as Eu₂O₃ (amount: 0.167 at.%) and Pr₂O₃ (amounts: 0.05 and 0.25 at.%) oxides. The glass samples of high chemical purity and optical quality were obtained from corresponding polycrystalline compounds in the air atmosphere in platinum crucibles according to standard glass technology. Optical absorption, luminescence excitation and emission spectra of the Eu- and Pr-doped glasses with SrO–2B₂O₃ composition were investigated in the spectral range 300–800 nm at temperatures of 293 and 85 K. On the basis of optical spectra obtained and electron paramagnetic resonance (EPR) data analysis it is shown that Eu and Pr impurities are incorporated into the SrO–2B₂O₃ glass network as Eu³⁺ (4f⁶, ⁷F₀) and Pr³⁺ (4f², ³H₄) ions, exclusively. All the observed transitions of the Eu³⁺ and Pr³⁺ centres in absorption and luminescence spectra were identified. The luminescence kinetics of Eu³⁺ and Pr³⁺ centres were investigated and analysed. The decay constants for main emission transitions in all samples investigated were obtained at room temperature. Peculiarities of incorporating the Eu³⁺ and Pr³⁺ activator ions in the glass with SrO–2B₂O₃ composition and their optical spectra are discussed in comparison with rare-earth doped polycrystalline compounds and single crystals with the same (SrB₄O₇) composition and other borate glasses.