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Scintillators based on ZnSxSe1–x are promising materials for X-ray and γ-ray detection. For optoelectronic devices, it is better to use semiconductor compounds with a direct-zone energy structure with its spectral range lying in the fundamental absorption region. The band gap in such semiconductors is an important parameter that affects the energy resolution, ionization energy, dark current and other scintillation characteristics. The effect of sulfur content on the optical width of the band gap in mixed crystals ZnSxSe1–x is investigated in this paper. The test samples for this study were grown by Bridgman-Stockbarger in graphite crucibles with the diameter of 25 mm in the Ar atmosphere (PAr = 2·106 Pa) at a temperature from 1870 to 2000 K, depending on the composition of the initial raw materials. Six samples with different content of components were obtained: ZnS0,07Se0,93; ZnS0,15Se0,85; ZnS0,22Se0,78; ZnS0,28Se0,72; ZnS0,32Se0,68; ZnS0,39Se0,61. The transmittance of the samples in the range from 61 to 67% at 1100 nm (sample thickness 4 mm) indicates a high optical quality of the crystals. It was established that the optical width of the band gap for mixed crystals ZnSxSe1–x increases from 2.59 to 2.78 eV with increasing sulfur content from 0.07 to 0.39 for direct transitions and from 2.49 to 2.70 eV for indirect transitions. A comparison was made between theoretical and experimentally obtained values of the band gap width. It is shown that no new (defective) levels appear in the band gap. The smooth dependence of the optical band gap on the composition indicate a possibility of growing ZnSxSe1–x mixed crystals by directional solidification techniques for X-ray and γ-ray detectors. The wider band gap and higer atomic mass ratio of ZnSxSe1–x crystals, as compared to ZnSe(Te) or/and ZnSe(Al) crystals, extend application areas of such semiconductor material.

Composite materials based on ZnSxSe1–x solid solutions are promising materials for gamma and X-ray detectors. However, influence of compositions and particle size on scintillation properties is unclear, which prevents their application. This paper reports on the complex study of microcrystalline ZnSxSe1–x powdered scintillations, prepared by solid phase synthesis from ZnS and ZnSe initial compounds. ZnSxSe1–x solid solutions were obtained in the range of x from 0.07 to 0.86 and in the following sizes: 200—250 μm, 140—200 μm, 140—80 μm, and less than 80 μm. X-ray diffractions of powder ZnSxSe1–x shows formation of a cubic lattice of sphalerite structure. ZnSxSe1–x powders demonstrate a presence of a luminescence band in the 590-615 nm regions, while an increase in sulfur concentration leads to a shift of the maximum intensity of X-ray induced luminescence to the short-wave region, which is associated with an increase of the band gap width. The best parameters of X-ray induced luminescence are obtained for the solid solution with 39 at.% of sulfur. The ZnS0,39Se0,61 solid solutions obtained under these conditions have an X-ray induced luminescence intensity that is 4 times higher than that of ZnSe(Al) single crystal and a relatively low level of afterglow. In ZnSxSe1–x solid solutions, increasing of particle size leads to shifts of the X-ray induced luminescence to the longwave region. The highest intensity of the X-ray induced luminescence corresponds to the ZnS0,39Se0,61 composition with the particle size of less than 80 μm. Also, ZnS0,39Se0,61 solid solutions, with particle size less than 80 microns, are more homogeneous in composition, which is why the process of solid phase reaction in them passes more efficiently. It is shown that the ZnSxSe1–x composite scintillators can be used as gamma and X-ray detectors. It has been established that the effectiveness of these materials depends on their composition. ZnS0,5Se0,5 and ZnS0,39Se0,61 composites demonstrate the best scintillation characteristics, with twice as high an efficiency as that of the «commercial» ZnSe(Al) composite.

ZnSxSe1–x based luminescent materials are promising for use as X-ray and γ-ray detectors. The main advantage of ZnSxSe1–x crystals is the possibility of making of solid solutions over an entire X-range. It was found that varying the composition of ZnSxSe1–x crystals can change their luminescent properties. Many studies were focused on obtaining ZnSxSe1–x mixed crystals, most using a vapour phase growth methods, and only some of works used the directional solidification. The directional solidification techniques allow growing large ZnSxSe1–x crystals for high-energy particles detectors. Practical use, however, requires the knowledge about luminescent properties of ZnSxSe1–x bulk crystals. This study reports the effect of sulfur content on basic properties of ZnSxSe1–xx bulk crystals grown by Bridgman- Stockbarger method. Six different compounds were studied: ZnS0.07Se0.93, ZnS0.15Se0.85, ZnS0.22Se0.78, ZnS0.28Se0.72, ZnS0.32Se0.68, ZnS0.39Se0.61. The ZnSe(Al) and ZnSe(Te) crystals grown at the similar conditions were used as reference. X-ray luminescence was studied using РЕИС-И (REIS-I) X-ray source (Cu, U = 10—45 kV). КСВУ-23 (KSVU-23) spectrophotometer was used to analyse the emission spectra. The afterglow level η (%) was determined by Smiths Heimann AMS-1 spectrophotometer at excitation by such X-ray and γ-ray sources as 123Cs and 241Am (59.5 keV). Light output is one of the main characteristics of the scintillator, which determines its quality as a detector. The ZnSxSe1–x crystals demonstrated increase in the intensity of X-ray induced luminescence spectra with increasing of sulfur content and reached maximum for ZnS0.22Se0.78 composition. Light output of ZnSxSe1–x bulk crystals are higher than those of ZnSe(Te) and ZnSe(Al) commercial crystals. Moreover, thermal stability of scintillation light output of ZnSxSe1–x bulk crystals are also better than those. This investigation has revealed that basic properties of ZnSxSe1–x based scintillation detectors are better than those of ZnSe(Te) and ZnSe(Al).