S. Kh. Batygov

VUV 5d-4f luminescence of Gd3+ and Lu3+ ions in the CaF2 host

The first observation and characterization of Lu3+ 4f135d-4f14 luminescence from the CaF2: Lu3+ crystal are reported, and the multisite structure in the spectra of Ce3+, Gd3+, and Lu3+ ions in the CaF2 host is analyzed with the high-resolution VUV spectroscopy technique using synchrotron radiation. It is shown that vibronic structure in the emission and excitation spectra of interconfigurational transitions in Gd3+ and Lu3+ ions doped into CaF2 differs from that observed for Ce3+ ions entering mainly at the tetragonal (C4v) sites. However, the exact types of sites in which the Gd3+ and Lu3+ ions reside in a CaF2 lattice cannot be identified using only the obtained experimental spectroscopid data.

Preparation and properties of heavy-metal halide glasses

We have studied the effect of In3+, Pb2+, Gd3+, and Cl (heavier ions) substitutions for Al3+, Ba2+, La3+, and F− on the crystallization stability and UV/IR optical properties of HBLAN fluorohafnatc glasses (HfF4-BaF2-LaF3-AlF3-NaF system). We obtained stable glasses containing InF3 and BaCl2 instead of AlF3 and BaF2, respectively, and offering increased IR transmission. The presence of CCl4 in the process atmosphere and the removal of oxygen-containing impurities via directional solidification are shown to have an advantageous effect on the optical quality of the glasses. The fluoride-chloride glasses are capable of accommodating about 1.5 times higher levels of rare-earth activators in comparison with their fluoride analogs.

Optical properties of europium-activated hafnium fluoride-based glasses

We have studied the optical absorption, luminescence, and electron paramagnetic resonance of EuF3- and EuF2-activated fluorohafnate glasses. The glasses prepared with EuF2 contain both di- and trivalent europium. The fraction of divalent europium clusters in the glass host decreases with decreasing EuF2 concentration. Eu2+ luminescence in the fluorohafnate glasses is quenched, which is due the overlap of Eu2+ excited state levels with the conduction band of the glass, resulting in nonradiative relaxation through Hf3+ levels in the conduction band. The Eu3+ luminescence spectra contain lines corresponding to transitions from several levels of the 5D multiplet to levels of the 7F multiplet. The relationship between transitions from different 5D levels depends on europium concentration and temperature.

Glasses on the basis of heavy metal fluorides

In this review, the information on glass-forming fluoride systems is presented, and the main methods for synthesizing glasses on the basis of fluorides of the metals of Groups I–IV, their physicochemical properties, techniques for producing fibers and areas of application, and the techniques for purifying them from undesired impurities are discussed. Modern materials science studies in the area of fluoride glasses are aimed at searching for glasses activated with rare-earth elements (REEs) with a broad IR transmission range and high optical homogeneity with the purpose of creating efficient active optical media in a wide spectral range, as well as converters of IR radiation into the visible range for enhancing the efficiency of solar cells and exciting photocatalysts. The analysis of the influence of impurities on the optical transparency, crystallization, and phase purity of the glasses under study is presented. The methods for the deep purification of the initial substances for preparing fluoride glasses with the minimum content of impurities are considered. Original procedures for synthesizing fluorides of elements and glasses free from oxygen-containing impurities are created on the basis of physicochemical studies of the interactions of fluorinating agents with the components of fluoride glasses.

Crystallization behavior of hafnium fluoride-based fluorochloride glasses

The crystallization mechanism of chlorine-containing fluorohafnate glasses with the compositions (65–56)HfF4 · (20–x)BaF2 · xBaCl2 · 4LaF3 · (3–y)AlF3 · yInF3 · (5–18)NaF has been studied by X-ray diffraction and differential thermal analysis. The results demonstrate that characteristic features of the glasses are a decrease in glass transition temperature and the precipitation of fine-particle crystalline chloride phases at temperatures below the crystallization temperature of their fluoride analogs. We have studied the effect of the Cl/F ratio in the glass batch and the melt cooling rate on the crystallization behavior of the glasses and determined the heat treatment temperature and time for the formation of transparent glassceramic materials. The luminescence properties of Er3+-doped fluoride and fluorochloride glasses and glassceramics prepared from them have been investigated in the 1.5-µm range.

Luminescence of Ba1–xLaxF2 + x: Ce3+ crystals

The luminescence of BaF2 crystals with various concentrations of cerium and lanthanum is studied under excitation with X-rays and UV radiation. In the X-ray luminescence spectra of BaF2–Сe3+ crystals, luminescence quenching is observed at a concentration of cerium above 0.1%. In Ba1–xLaxF2 + x: Ce3+ crystals, an increase in the concentration of lanthanum at a constant concentration of cerium leads to the same X-ray luminescence quenching as that caused by a similar increase in the concentration of cerium. No corresponding concentration luminescence quenching occurs under photoexcitation. The results show that luminescence quenching under X-ray excitation is primarily caused by energy loss at the stage of the transfer of the energy from the matrix to the dopant rather than by the transfer of the energy from excited cerium ions to quenching centers.

Scintillating Fluorohafnate Glasses

Data are presented on the roentgenoluminescence and gamma-radiation resistance of Ce3+-doped fluorohafnate glasses prepared under different redox conditions and containing different additions. The glasses are shown to contain several types of luminescence centers and radiation-induced color centers, whose concentrations are governed by the preparation conditions and the nature of the dopants. The radiation resistance and light output of the glasses can be notably enhanced by optimizing the preparation conditions and introducing certain additions.

Luminescence of Ba1–x La x F2 + x : Ce3+ crystals

The luminescence of BaF2 crystals with various concentrations of cerium and lanthanum is studied under excitation with X-rays and UV radiation. In the X-ray luminescence spectra of BaF2–Сe3+ crystals, luminescence quenching is observed at a concentration of cerium above 0.1%. In Ba1–xLaxF2 + x: Ce3+ crystals, an increase in the concentration of lanthanum at a constant concentration of cerium leads to the same X-ray luminescence quenching as that caused by a similar increase in the concentration of cerium. No corresponding concentration luminescence quenching occurs under photoexcitation. The results show that luminescence quenching under X-ray excitation is primarily caused by energy loss at the stage of the transfer of the energy from the matrix to the dopant rather than by the transfer of the energy from excited cerium ions to quenching centers.

Luminescence of Ba 1– x La x F 2 + x : Ce 3+ crystals

The luminescence of BaF2 crystals with various concentrations of cerium and lanthanum is studied under excitation with X-rays and UV radiation. In the X-ray luminescence spectra of BaF2–Сe3+ crystals, luminescence quenching is observed at a concentration of cerium above 0.1%. In Ba1–xLaxF2 + x: Ce3+ crystals, an increase in the concentration of lanthanum at a constant concentration of cerium leads to the same X-ray luminescence quenching as that caused by a similar increase in the concentration of cerium. No corresponding concentration luminescence quenching occurs under photoexcitation. The results show that luminescence quenching under X-ray excitation is primarily caused by energy loss at the stage of the transfer of the energy from the matrix to the dopant rather than by the transfer of the energy from excited cerium ions to quenching centers.

Intrinsic X-ray Luminescence of Fluorohafnate Glasses

The influence of the atmosphere used in glass synthesis and dopants on X-ray luminescence of fluorohafnate glasses in the HfF4–BaF2–Ce(La)F3–AlF3–NaF–InF3 system is investigated. Upon introduction of certain oxides, the X-ray luminescence spectrum exhibits a broad band with a maximum at 360 nm. A similar band appears in the spectra in the case when the glasses are synthesized under reducing conditions. The appearance of the 360-nm luminescence band is observed both in the spectra of glasses activated by cerium and in the spectra of nonactivated glasses. It is assumed that the appearance of this band is associated with the formation of Hf3+ ions and fluorine vacancies in the glass under investigation.