Purpose. To obtain Cs2LiYCl6:Ce (CLYC) single crystals used to detect slow neutrons. The technology allows obtaining single crystals for detecting slow neutrons, which are used as a working element of detectors applied at nuclear power plants. CLYC has a light output of 21,000 photons per MeV with a scintillation decay time of 35 ns (fast component), while other single crystals for detecting slow (thermal) neurons, such as lithium iodide activated by europium, have a light output of 15,000 photons per MeV with 00 ns. At the same time, the lithium content in LiI:Eu is higher than that of CLYC.
Technical properties. The technology allows obtaining transparent single-crystal samples of Cs2LiYCl6: Ce with a diameter of 12-15 mm and a length of up to 50 mm. The capacity of one process line is 40 single crystals per year.
Application area. Inorganic substance technology, single crystal growth.
Advantages. Due to additional purification at the melt stage, the technology allows to obtain CLYC single crystals with improved functional characteristics. To grow CLYC single crystals, the batch is purified from oxygen-containing impurities to ensure improved performance properties of the end CLYC single crystals. When drying the batch, the following processes can occur: RCl3 + H2O = ROCl + 2HCl (R=Y, Ce). Treating the melt with tetrachloromethane (CCl4) removes oxygen-containing impurities, which allows to obtain CLYC single crystals with improved functional characteristics. This process can be described by the following equation: 2ROCl + ССl4 ↑ = 2RCl3 + CO2 ↑ (R=Y, Ce). The main purpose of purification is to increase the light output and reduce the afterglow (fading time).
Technical and economic effect. The technology allows to obtain single crystals for neutron detection with improved performance characteristics. Using detectors to monitor the operation of nuclear power plants helps to improve the ecology of the environment.
Description. Y2O3 is dissolved in concentrated hydrochloric acid upon heating. Li2CO3 is dissolved separately in hydrochloric acid. The resulting solutions of YCl3 and LiCl are mixed and weighed portions of CsCl and CeCl3 are added. The resulting solution is evaporated until a crystalline film appears, then ammonium chloride is added. The resulting mixture is dried at 160 C and a CLYC batch with a small admixture of water is obtained. Then drying is carried out in a quartz container in a vacuum. When drying the batch, the following processes are possible: RCl3 + H2O = ROCl + 2HCl (R = Y, Ce). As a result of this process, R-O bonds are formed, both by the matrix component and the activator, which worsens both the light output and the response time. As a rule, this is not dealt with. Treatment of the melt with tetrachloromethane (CCl4) leads to the removal of oxygen-containing impurities. For this, the dried batch is melted and the melt is heated to 800°C, a pair of tetrachloromethane in argon is passed through the melt until the melt becomes transparent. for growth.