Method and appts. of using molten lead iodide to grow monocrystal

Abstract

This invention discloses method and equipment for preparing lead iodide single crystals from lead iodide melt, which comprises the steps of: cleaning an ampule, filling it with lead iodide powders, degassing and sealing the ampule, growing the single crystals and cooling. The method can effectively suppress the decomposition of lead iodide melt and the vaporization of iodine, and can remove segregated lead. The ampule is made of a quartz tube, and comprises a seed crystal bag, a growth chamber, a connecting vessel, a lead tube, a loading bag anb a hook. After filling, the ampule is placed into a two-stage temperature range vertical tubular furnace to finish the growth of the single crystals. The as-grown single crystals are orange and semi-transparent with sizes up to Phi (15-20)X30 mm. The electrical resistivity of as-grown single crystals can reach 1012-1013 ohm .cm, thus the single crystals have wide applications, especially as room temperature nuclear radiation detector.

Description

Technical field: [0001] The invention belongs to the field of single crystal preparation, in particular to a method for growing a single crystal by using lead iodide melt. technical background: [0002] Lead iodide (PbI 2 ) single crystal belongs to the hexagonal crystal system, and is an orange-red translucent wide bandgap semiconductor material. 2 The band gap of the crystal is about 2.3-2.5eV, and it has a high resistivity. It has great application potential in optical information recording systems and nonlinear optical systems. It can be used to make photocells and scintillation crystal photodetectors working at high temperatures. etc.; PbI 2 The atomic number is large (Z Pb =82, Z I =53), which has high stopping power for high-energy rays, and is one of the most promising materials for making room temperature x-ray (or gamma-ray) detectors. with the same type of HgI 2 crystal compared to PbI 2 The crystal has a larger forbidden band width, a much lower vapor pres...

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Problems solved by technology

[0013] The melt method has two disadvantages: one is that the melt is in direct contact with the remaining space above the ampoule, which provides conditions for the decomposition of lead iodide and the evaporation of iodine, even if an inert gas is filled in the remaining space above the ampoule. The decomposition of lead iodide and the evaporation of iodine cannot be completely suppressed; the second is that the solidification direction (crystal growth direction) of the melt is inconsistent with the precipitation direction of segregated lead in the melt. In the vertical Bridgman method, the crystal growth direction is the same as The precipitation direction of segregated lead is opposite. In the horizontal area smelting method and the moving melting zone method, the crystal growth direction is perpendicular to the precipitation direction of segregated lead, which is not conducive to the discharge of segregated lead, and it is difficult to obtain high-quality lead iodide single crystal

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