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Inorganic phosphors based on rare earth elements are commonly used as scintillation materials due to their high chemical and radiation resistance. In this work, we study gadolinium oxyselenide as a new phosphor material. The work describes a facile synthesis method for Gd 2 O 2 Se. Single crystal structure of this compound was determined for the first time: sp.gr. P ¯3 m 1 with a ​= ​3.8911(4) Å and c ​= ​6.8829(8) Å. Gd 2 O 2 Se is stable in the inert atmosphere and melts at 2075 ​± ​20 ​°C. This material is also stable when heated in air up to 720 ​°C. with the following oxidation and weight increase. This mass increase can be explained by the oxidation of Se2− to Se4+. Further temperature increase above 952°С leads to a sharp mass loss and the final mass of sample corresponds to full oxidation of Gd 2 O 2 Se to gadolinium oxide. The band gap of the material was estimated to be 3.6 ​eV. Photoluminescence spectrum for Gd 2 O 2 Se:Tb3+ shows the characteristic transitions in Tb3+ ion with the most intense green emission that corresponds 5D 4 → 7F J transitions. [Display omitted] • A powder of Gd 2 O 2 Se was obtained and the single crystal structure was determined: sp.gr. P ¯3 m 1, a ​= ​3.89Å, c ​= ​6.88 Å. • The melting point was found to be 2075 ​± ​20 ​°C. High air stability for this compound was demonstrated up to 720 ​°C. • The estimated value of the band gap is 3.6 ​eV. The photoluminescence of the Tb3+ doped sample was investigated. [ABSTRACT FROM AUTHOR]

• The optical constants of Lu 2 O 3 single crystals covering the UV–VIS–NIR spectral region are firstly investigated • The bandgap energy 5.541 ± 0.004 eV of Lu 2 O 3 single crystal is derived experimentally • Large-size and damage-free Lu 2 O 3 single crystal is obtained by chemical mechanical polishing Lu 2 O 3 has attracted widespread attention in high-power lasers, scintillators, and semiconductors due to its high thermal conductivity, high stability, and large band gap. Due to the limitations of the growth process, high-precision characterization of polished quality and optical properties for large-size Lu 2 O 3 single crystal is extremely scarce, which hinders the design and optimization of optics based on Lu 2 O 3. In this study, we design a systematic machining scheme for large-size Lu 2 O 3 single crystal thick chip to obtain polished crystal with virtually no surface and subsurface damage. The surface/subsurface quality was evaluated utilizing optical profilometer, scanning electron microscope, and transmission electron microscope. Variable-angle spectroscopic ellipsometer was employed to measure the optical constants over wide spectral region (210–1690 nm), removing the lack of optical constants of Lu 2 O 3 single crystal in the ultraviolet region. The band gap is analyzed based on the optical constants results. The consistency of the measured data with the relevant literature verifies the reliability and accuracy of the measurement method along with the data. The surface/subsurface damage inspection method provides an effective approach for ultra-precision machining mechanism research and process optimization of Lu 2 O 3 and other hard and brittle materials. The band gap and the optical constants in wide spectral region provide critical fundamental data for the design and performance optimization of related optics. [ABSTRACT FROM AUTHOR]

ZnS nanopowders have been synthesized by chemical deposition from aqueous solutions of zinc nitrate and sodium sulfide in the presence of sodium citrate or Trilon B. Ag 2 S/ZnS heteronanostructures have been prepared by co-deposition of zinc and silver sulfides. The size of nanoparticles in the deposited powders has been estimated by X-ray diffraction and transmission electron microscopy. A change in the ratio between the concentrations of reagents in the reaction mixtures made it possible to obtain ZnS nanopowders with an average particle size of 2–10 nm. The size of the nanoparticles in the prepared heteronanostructures is 8–10 nm. The diffuse reflection spectra have been measured and the corresponding absorption spectra of nanostructured ZnS and Ag 2 S/ZnS heteronanostructures have been analyzed using Tauc plots. The optical band gap E g of the studied sulfide nanostructures has been estimated. A blue shift of the optical absorption edge and an increase in the E g values from 3.59 to 3.72 eV are observed with a decrease in the size of ZnS nanoparticles. An increase in the Ag 2 S content in Ag 2 S/ZnS heteronanostructures leads to a decrease in the optical band gap. Pulsed cathodoluminescence of nanostructured ZnS and Ag 2 S/ZnS heteronanostructures have been investigated. It is found that the maxima of the luminescence spectra of nanostructured zinc sulfide are located at about 450 nm. Prepared samples of nanostructured ZnS possess a very short decay time and thanks to this property the prepared ZnS nanostructures can be used as a material for scintillation detectors. Image 1 • ZnS and Ag 2 S/ZnS heteronanostructures are synthesized by chemical deposition. • Band gap of ZnS at decreasing particle of 10 to 2 nm varies from 3.6 to 3.7 eV. • Adding Ag 2 S to ZnS leads to much larger change of the band gap E g. • An increase in x for (ZnS)·(Ag 2 S) x from 0 to 0.1 reduces E g from 3.6 to 2.1 eV. [ABSTRACT FROM AUTHOR]