The results of the synthesis and study of the spectral and structural properties of borate glasses with (Cs,Rb)PbBr3 perovskite nanocrystals are presented. (Cs,Rb)PbBr3 nanocrystals exhibit intense narrow-band luminescence in the 510–520 nm region. With an increase in the rubidium content, the luminescence maximum of the crystals shifts to the short-wavelength region, while the luminescence quantum yield first increases to 91% and then decreases to 52%. In the rubidium absence, several perovskite-like phases of lead-cesium bromides are nucleated in the glass matrix: CsPb2Br5, Cs4PbBr6, and CsPbBr3, while with the increase of the rubidium the CsPbBr3 phase predominates. The glass matrix protects the (Cs,Rb)PbBr3 nanocrystals from the ambient atmosphere, which leads to the stability of their luminescence intensity.
This work is devoted to investigation of the spectral and luminescent properties of lithium-germanate, lithium-sodium germanate and lithium-zinc-germanate glass ceramics obtained by high-temperature heat treatment of the initial glass doped with manganese and chromium ions. It is shown that when sodium is added to Mn-doped lithium germanate glass-ceramics, the luminescence intensity of Mn4+ ions increases from 5 to 37% of the quantum yield. In lithium-zinc-germanate glass-ceramics, the simultaneous presence of Mn4+ ions in an octahedral environment with red luminescence near 670 nm and Mn2+ ions in a tetragonal environment with long persistent green luminescence at 540 nm is found. The maximum quantum yield for red luminescence was 47%, for green luminescence – 23%. The intensity ratio of different luminescence bands depends on the ratio of lithium / zinc ions in the glass composition. In all studied glass-ceramics, Cr3+ ions demonstrate weak luminescence with a maximum in the region of 690–698 nm. The possibility of using the materials under study as a luminescent red radiation source material is considered.
The aim of this work is to investigate temperature effect on spectral properties CsPbI3 perovskite nanocrystals nucleated in borogermanate glass by isothermal heat treatment at different temperatures. The temperature dependence of the first exciton absorption intensity in the heating-cooling cycle has a form of hysteresis loop, which helps determine crystallization and melting temperatures. Considering anomalies on heat curves, a phase transition from a non-perovskite to a cubic crystal structure is found in the range of 420-460℃. The increase of initial nucleation temperature from 470 to 550℃ results in a change of phase transitions temperatures: melting, crystallization, and transition from a non-perovskite to a cubic crystal structure increase in the regions 454-475, 281-301 and 421-459℃ respectively due to quantum-sized effect. Results demonstrate that the cesium lead halide perovskite properties can be stabilized up to 440℃, which greatly exceeds the chemical resistance of perovskites in organic matrix.
This work is devoted to the study of phase transitions in CsPbBr3 perovskite nanocrystals nucleated in borogermanate glass. Perovskite nanocrystals are obtained by bulk crystallization in a glass matrix. A series of glass samples with nanocrystals of different sizes is investigated. Upon heating, the temperature dependence of the 1S exciton intensity for the entire series of samples shows the presence of three phase transitions: in the range 130-150, 440-450, and 510-515°C. The first phase transition refers to the transition from a tetragonal to a cubic structure. The last phase transition is associated with the melting of the crystalline phase. The phase transition at 440°С is declared for the first time. Upon cooling, the temperature curve shows the presence of only one phase transition in the region of 330°C, which is associated with the crystallization onset of CsPbBr3 perovskite nanocrystals in glass matrix.
This work is devoted to investigation of the temperature influence on the spectral and luminescent properties of borate glass ceramics obtained by high-temperature heat treatment of the initial glass containing chromium oxide. The luminescence and absorption spectra are obtained for samples with different concentrations of antimony oxide, which plays the role of a reducing agent, during heating and subsequent cooling. The dependence of the luminescence intensity on temperature is established. The possibility of using the materials under study as luminescent temperature sensors is considered.
Mixed-alkali-alumina-borate glasses doped with different Cr2O3 content are prepared by conventional melt-quenching technique. Luminescent glass-ceramics is derived by volume crystallization of the precursor glass via two-stage heat treatment. The structural, spectral, and luminescent properties of the glass-ceramics are determined by X-ray diffraction, optical absorption, and photoluminescent spectroscopy. The XRD studies reveal the LiAl7B4O17: Cr3+ nanocrystals nucleation during the heat treatment. The photoluminescence spectra consist of three intense bands in the 685 – 715 nm region. The features and background of the complex concentration dependence of the luminescence lifetime are discussed. The maximum quantum yield value under 532 nm excitation is 41%.
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