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ZnSe1-xSx crystals with a higher content of selenium or sulfur ions adopt, respectively, a wurtzite or sphalerite structure. Luminescent properties of ZnSe1-xSx crystals are determined by ternary VZnZniOSe complexes for crystals with a cubic (sphalerite) lattice, and by sulfur vacancies VS for crystals with a hexagonal (wurtzite) lattice. Light output of ZnSe1-xSx crystals increases with increasing the sulfur content up to x = 0.3 and reaches the value of light output observed for ‘classic scintillator’ ZnSe(Te). At the same time, the ZnSe1-xSx bulk crystals possess better thermal stability at the same energy of emitted photons (hν ~ 2 eV) as compared to that of the ZnSe(Te) crystals.

ZnS Se1− bulk crystals were grown by the Bridgman-Stockbarger method. The transmittance of different samples in the range from 67% to 56% at = 1100 nm (for 4-mm samples) indicates a high optical quality of the crystals. No new states were revealed at the sulfur incorporation, and the band gap depends on the composition. The optical band gap of ZnS Se1− bulk crystals varies from 2.59 to 2.78 eV for direct transitions and from 2.49 to 2.70 eV for indirect transitions. K e y w o r d s: ZnS Se1− bulk crystals, direct transitions, indirect transitions, band gap.

A possibility to use ZnSxSe1−x as a material for the detection of X-rays and alpha particles has been studied. The influence of the sulfur content on the properties of bulk ZnSxSe1−x crystals is analyzed. Six specimens with different component contents were grown, by using the Bridgman–Stockbarger method: ZnS0.07Se0.93, ZnS0.15Se0.85, ZnS0.22Se0.78, ZnS0.28Se0.72, ZnS0.32Se0.68, and ZnS0.39Se0.61. The intensity of X-ray luminescence spectra of ZnSxSe1−x crystals is found to increase with the sulfur content and reaches a maximum for the composition ZnS0.22Se0.78. The luminescence light yield of mixed ZnSxSe1−x crystals is higher than that of commercial ZnSe(Te) and ZnSe(Al) crystals. The advantages of mixed crystals based onZnSxSe1−x over the ZnS(Te) and ZnSe(Al) crystals have been discussed.

ZnSxSe1–x based luminescent materials are promising for use as X-ray and g-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 h(%) was determined by Smiths Heimann AMS-1 spectrophotometer at excitation by such X-ray and g-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).