Marcin Środa

Spectroscopic properties of transparent Er-doped oxyfluoride glass–ceramics with GdF3

Optically active glass-ceramics (GC) with the low-phonon phases of fluorides, doped with Er(3+) was studied. Glass based on SiO₂-Al₂O₃-Na₂F₂-Na₂O-GdF₃-BaO system was obtained. Dopant were introduced to the glass in an amount of 0.01 mol Er₂O₃ per 1 mol of glass. DTA/DSC study shows multi-stage crystallization. XRD identification of obtained phases did not confirm the presence of pure GdF₃ phase. Instead of that ceramization process led to formation of NaGdF₄ and BaGdF₅. The structural changes were studied using FT-IR spectroscopic method. The study of luminescence of the samples confirmed that optical properties of the obtained GC depend on crystallizing phases during ceramization. Time resolved spectroscopy of Er-doped glass showed the 3 and 8 times increase of lifetime of emission from (4)S₃/₂ and (4)F₉/₂ states, respectively. It confirms the erbium ions have ability to locate in the low phonon gadolinium-based crystallites. The results give possibility to obtain a new material for optoelectronic application.

Influence of fluorine on thermal properties of lead oxyfluoride glass

Oxyfluoride glasses are the basic materials for obtaining transparent glass–ceramic (TGC) which can be used in a wide range of optoelectronics devices such as: amplifiers, up-conversion, telescopes, laser sources. Oxyfluoride TGC is obtained by the control heat treatment of the parent glass due to low phonon nanocrystalline phases. The oxyfluoride glasses from the sodium–lead–silica system were the object of investigation. The influence of fluoride content on the thermal properties of glasses was analyzed. Thermal characteristics of glasses like the transition temperature Tg, the temperature for the crystallization onset Tx, and the maximum crystallization temperature Tc, thermal stability parameter were determined by DTA/DSC method. The linear expansion coefficients of oxyfluoride glasses as a function of temperature were measured using a thermo-mechanical analyzer (TMA 7 Perkin-Elmer). The effect of crystallization on the thermal expansion coefficient and softening temperature Ts was found.

Thermal Methods Applied to the Glass Transition of Mixed Network AlPO4–BPO4–SiO2 Glasses

Glass transition effect of mixed network AlPO4–BPO4–SiO2 glasses was studied. DTA/DSC and TMA measurements has been applied in the research. It has been found that glass transition effect has structurally sensitive properties. Glass transition temperature Tg, changes of specific heat (Δcp)and thermal expansion coefficient (α) accompanying the process depend on the nature and the number of components forming the glassy framework. Character of chemical bonds combining them into the glass structure has an influence on the glass transition effect. Its course is dependent on the flexibility of the structure of glasses.

Influence of Gd2O3 on thermal stability of oxyfluoride glasses

The aim of the research was to determine the influence of Gd2O3 addition on the thermal stability of glasses from BaF2–NaF–Na2O–Gd2O3–Al2O3–SiO2 system. Thermal analysis was carried out using DSC method. An impact of Gd2O3 on thermal parameters such as transformation temperature (Tg), onset temperature of crystallization (Tx), peak crystallization temperature (Tp), change of specific heat (ΔCp) and enthalpy of crystallization (ΔH) was determined. On the basis of thermal analysis, controlled crystallization was conducted. The glass-ceramic materials were identified by XRD. Crystallization kinetics of the glasses was made on the basis of two models: Kissinger and Ozawa. Changes of the glass structure were evaluated in FTIR study. It was determined that the addition of Gd2O3 to the aluminosilicate glass increases the transformation temperature, simultaneously with reducing the Δcp and thermal stability ΔT values. It results in the decrease of ΔH. As shown, Gd significantly increases the crystallization activation energy of NaAlSi3O8. Complete substitution of Al2O3 with Gd2O3 leads to forming of Gd9.33(SiO4)6O2. Forming of Na-silicates is not observed. Because of the participation of Gd in forming of fluoride phases (BaGdF5, GdF3), crystallization of Gd9.33(SiO4)6O2 is impeded.

Time resolved spectroscopy of oxyfluoride glass ceramics activated by Pr3+ ions

The paper presents a new glass ceramics of the SiO2-B2O3-Na2O-LaF3 system in which nanocrystallization of LaF3 could be obtained. Thermal stability of glass and the crystalline phases formed upon heat treatment were determined by DTA/DSC and XRD methods, respectively. The effect of incoming of Pr3+ to LaF3 crystals in the glassy host has been shown in the emission spectra. The 3P0 → 3HJ emissions have been much stronger in glass-ceramics what supports the suggestion that 3P0 → 1D2 non-radiative decay dominates the relaxation of 3P0 for Pr3+ ions in the as-made glass.