A. Drzewiecki

Synthesis and X-ray structural investigation of undoped borate glasses

A series of undoped borate glasses: Li2B4O7, LiKB4O7, LiB3O5, SrB4O7, and LiCaBO3 of high optical quality and chemical purity were obtained from the corresponding polycrystalline compounds using standard glass synthesis under technological conditions developed by the authors. The glasses were obtained by rapid cooling of molten crystalline material, which was heated to 100 K above the melting point to prevent crystallization and to exceed the glass transition point. The X-ray diffraction intensity profiles of the investigated glasses were typical of glassy compounds. The most typical intensity profile, consisting of almost symmetrical peaks, was observed in the case of Li2B4O7 and LiB3O5. Substitution and partial substitution of Li atoms by Sr and Ca atoms was accompanied by significant changes in the intensity profiles of the investigated glasses. Pair correlation functions and structural parameters (average interatomic distances and coordination number to oxygen) of the investigated glasses were evaluated and analyzed. Structural peculiarities of the investigated borate glasses are discussed in comparison with structural data available for their crystalline analogs.

Synthesis and optical spectroscopy of borate glasses, doped with terbium and dysprosium

The high optical quality glasses with CaB4O<inf>7</inf>:Tb, LiCaBO<inf>3</inf>:Tb, CaB<inf>4</inf>O<inf>7</inf>:Dy, and LiCaBO<inf>3</inf>:Dy compositions containing 0.5 and 1.0 mol. % Tb<inf>2</inf>O<inf>3</inf> and Dy<inf>2</inf>O<inf>3</inf> have been obtained. By electron paramagnetic resonance (EPR) and optical spectroscopy it was shown that the Tb and Dy impurities are incorporated in the CaB<inf>4</inf>O<inf>7</inf> and LiCaBO<inf>3</inf> glass network as Tb³⁺ (4f⁸, ⁷F<inf>6</inf>) and Dy³⁺ (4f⁹, ⁶H<inf>15/2</inf>) ions, exclusively. All observed f - f transitions of Tb³⁺ and Dy³⁺ centres in optical absorption, luminescence excitation and emission spectra have been identified. Luminescence kinetic shows single exponential decay for Tb³⁺ and Dy³⁺ centres in the CaB<inf>4</inf>O<inf>7</inf> and LiCaBO<inf>3</inf> glasses. Lifetimes for main emitting levels of Tb³⁺ and Dy³⁺ centres in all investigated glasses were determined at T = 300 K. Spectroscopy shows that obtained glasses are promising luminescent materials.

EPR and optical spectroscopy of the V-doped borate glasses

The series of V-doped glasses with Li₂O-2B₂O₃ (Li₂B₄O₇), 1/2(Li₂O-K₂O-4B₂O₃), (LiKB₄O₇), CaO-2B₂O₃ (CaB₄O₇) and 1/2(Li₂O-2CaO-B₂O₃) (LiCaBO₃) composition containing 0.5 and 1.0 mol. % V₂O₅ oxide were obtained by standard glass technology. The electron paramagnetic resonance (EPR) and optical absorption spectra of the obtained glasses were investigated at T = 300 K. The spin Hamiltonian parameters for observed EPR spectra in the Li₂B₄O₇:V, LiKB₄O₇:V, CaB₄O₇:V and LiCaBO₃:V glasses were determined and electron and local structure of impurity V centres were proposed. The optical absorption bands, observed in the investigated glasses have been interpreted.

Optical spectroscopy of borate glasses, doped with europium

The high optical quality glasses with Li₂B₄O₇:Eu, CaB₄O₇:Eu, and LiCaBO₃:Eu compositions containing 0.5 and 1.0 mol. % Eu₂O₃ have been obtained by standard glass technology. Using electron paramagnetic resonance (EPR) and optical spectroscopy it was shown that the Eu impurity is incorporated into the Li₂B₄O₇, CaB₄O₇, and LiCaBO₃ glasses network as Eu³⁺ (4f⁶, ⁷F₀) ions, exclusively. All observed f - f transitions of the Eu³⁺ centres in optical absorption, luminescence excitation and emission spectra were identified. Luminescence kinetic shows single exponential decay with different lifetimes for Eu³⁺ centres in the Li₂B₄O₇, CaB₄O₇, and LiCaBO₃ glasses.