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 polymer-salt method was applied to synthesize nanoscale Gd2O3:Nd3+ phosphors in the form of thin films on the inner surfaces of capillaries which organize the structure of a silica hollow-core anti-resonant optical fiber. To obtain luminescing centers, the preform of a hollow-core anti-resonant optical fiber was impregnated with a homogeneous mixture of Gd(NO3)3 and NdCl3 dissolved in water and organic solvent (polyvinylpyrrolidone). This procedure was followed by a few post-processing steps, including drying of the impregnated preform in normal conditions and its thermal treatment at temperature 1000 °C. As a result, Gd2O3:Nd3+-based thin films were produced inside the capillaries. Finally, the modified preform was drawn into the hollow-core anti-resonant optical fiber of 120 μm in diameter at temperature 1850 °C. The analysis of crystallographic structure of the initial Gd2O3:Nd3+ nanopowder and the same nanophosphor inside the fabricated fiber revealed the absence of structural and phase transformations of synthesized nanocrystals with an average size 35 nm after drawing. The data on spectral-luminescent properties of the fabricated fiber confirmed the presence of Gd2O3:Nd3+ nanophosphors in silica glass with the main emission peak at wavelength 1064 nm. Presented method of modifying the structure of a hollow-core anti-resonant optical fiber allows formation of active silica layers without using technologically complicated and expensive CVD processes.
The paper describes the polymer-salt method of neodymium-doped aluminum yttrium garnet (YAG:Nd) crystals formation inside the channels of a microstructured silica fiber preform. The crystals formation was performed through the impregnation of inner surfaces of the channels by aqueous solutions of thermally decomposable salts (yttrium nitrate, aluminum nitrate, neodymium chloride) and an organic polymer with subsequent processes of drying and thermal treatment at the temperature of 1100°C. The composite structure prepared was drawn into the fiber at the temperature of 2000°C. The X-ray diffraction analysis revealed the formation of YAG:Nd crystals from 25 nm to 37 nm in size in the silica glass matrix of the fiber. Measurement of the attenuation spectral dependence confirmed the presence of optical signal absorption bands inherent to Nd3+ ions. The shape of the nanocrystals luminescence spectrum is characteristic to the YAG:Nd with a peak at the wavelength of 1064 nm.
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