Growth technique for cadmium tungstate twinkling monocrystal with crucible descent method

Abstract

The invention discloses a process of cadmium tungstate scintillation single crystal growth by the Bridgman-Stockbarge method, and the technology belongs to the single crystal growth field. High-purity CdO(99.99 percent) and WO3(99.99 percent) are taken as the starting material; powder is made according to the mole ratio that CdO:WO3 is equal to 1:1; after through fully ballmilling and mixing, the powder is pressed into tablet with proper specification; the tablet is sintered for 2 to 6 hours at the high temperature of 1000 to 1150 DEG C; and CdWO4 ceramics-shaped polycrystalline tablet can be obtained. The seed crystal and the tablet are stored through a special platinum crucible with 0.1 to 0.3 mm of wall thickness; the crucible is positioned in a single crystal growth furnace after being sealed; the furnace temperature is controlled within 1340 to 1400 DEG C; the position of the crucible is adjusted to ensure the tablet and the top part of the seed crystal are weld to form a stable solid liquid interface with 20 to 60 DEG C / cm of temperature gradient; growth is performed by the Bridgman-Stockbarge method at a speed lower than 2 millimeters / hour; annealing treatment is performed to the grown crystal at the temperature of 950 to 1050 DEG C; and then the scintillation single crystal with high quality and large size can be obtained. The process effectively avoids the inherent harmful melt composition during the process of crystal growth from volatilizing, the melt composition during the process of crystal growth keeps invariable, and the process can be applied to the bath-growth of the cadmium tungstate single crystal with various specifications and shapes.

Description

technical field [0001] The invention belongs to the technical field of single crystal growth. Cadmium tungstate single crystal is a scintillating luminescent material with excellent luminescent properties. It has quite high luminous efficiency, high energy resolution, strong resistance to radiation damage, high material density, and no deliquescence. It can be widely used It is of great application value in nuclear medical imaging, industrial CT, safety inspection, petroleum logging, high-energy physics and other technical fields, especially in XCT, PET, SPECT and other nuclear medical imaging equipment. The technology of the invention can grow high-quality and large-size cadmium tungstate single crystals meeting practical needs. Background technique [0002] Cadmium tungstate single crystal (CdWO 4 , CWO) is a monoclinic crystal system, belongs to wolframite structure, space group P2 / C, density is 7.9g / cm 3 Compared with many other inorganic scintillation crystals, cadmi...

AI Technical Summary

Problems solved by technology

The inherent technical difficulties in the pulling method growth process of cadmium tungstate single crystal are: (1) due to the CdO and WO in the melt 3 There are different degrees of volatilization, which leads to the gradual deviation of the melt composition from the stoichiometric ratio, and the grown crystal is prone to produce various scattering particles, so that the remaining melt in the later stage can no longer meet the needs of single crystal growth; (2) in the crystal growth of the pulling method During the process, the relatively serious volatilization of CdO vapor will cause environmental pollution and cause chronic cadmium poisoning of operators; (3) cadmium tungstate single crystal has obvious cleavage characteristics, and the large solid-liquid interface temperature gradient leads to thermal stress in the crystal Relatively large, the grown single crystal is easy to crack along the (010) cleavage plane

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