Process for growing lead tungstate crystal by vertical gradient solidification method

Abstract

The invention relates to a technique for growing a lead tungstate crystal by a vertical gradient solidification method, which belongs to the field of single crystal growth. The technique is characterized by comprising the following steps of: mixing initiative raw materials uniformly, wherein the initiative raw materials are prepared according to the set polycrystalline ingot chemically metering components; placing the mixture into a crucible and presintering the mixture for 2 to 4 hours at the temperature of between 700 and 800 DEG C, wherein a definitely-oriented seed crystal is arranged at the lower end of the mixture; heating the mixture to 1,130 to 1,200 DEG C to melt the raw materials, wherein the temperature gradient near the seed crystal and the melt is 15 DEG C / cm and the temperature gradient in the melt is 8 DEG C / cm; cooling the mixture at a speed of 2 DEG C / h, so that the crystal starts to grow, wherein the speed is maintained until the growth ended. A technique for growingthe lead tungstate crystal by the vertical gradient solidification method has the advantages of simple process, high repeatability, capacity of controlling all the procedures in the whole growth process and contribution to industrialized production.

Description

technical field [0001] The invention relates to a vertical gradient solidification growth process of lead tungstate crystals, belonging to the field of single crystal growth. Background technique [0002] People began to study the luminescence characteristics of lead tungstate in 1948, and first reported the luminescence phenomenon of PWO powder. In 1975, the luminescence of PWO in crystal form was studied more carefully, and the results showed that the luminescence spectrum of PWO consists of a blue luminescence band and two green luminescence bands, and the blue luminescence increases with the increase of excitation energy. Groenink et al. found that the green emission of PWO is polarized, while the blue emission is not polarized. However, due to the low room-temperature luminous efficiency of PWO, the research on its luminescent properties has not attracted much attention for a long time, only limited to photoluminescence, and less after that. It was not until 1990 that...

AI Technical Summary

Problems solved by technology

The basic feature of the pulling method is that in the Czochralski single crystal furnace, the initial raw materials in the platinum crucible are melted by high-frequency or resistance heating, and then grow out a certain direction and Single crystals of a certain size have not yet achieved industrial growth, and there are still some problems: (1) Due to the large temperature gradient near the solid-liquid interface and the anisotropy of thermal expansion of the crystal itself, cracking is easy to occur, so the seeds The crystal direction needs to be limited (generally grow along the b-axis); (2) The crucible is open, tungsten oxide is easy to volatilize, and the melt composition deviates seriously, resulting in low crystal yield and prone to macroscopic defects such as wrapping and color cores; (3) Stand-alone production, low efficiency, high production cost

But it is not suitable for strongly corrosive materials and crystals with negative expansion coefficient; the growth process will introduce large internal stress

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