Single crystal growth method of monopotassium phosphate with large caliber and high quality

Abstract

The invention relates to a single crystal growth method of monopotassium phosphate with large caliber and high quality, comprising the following steps: when seed crystal forms a cone, initial growth temperature lowers to the temperature of 0.5 DEG C below solution saturating point, and cone forming begins; cooling rate is controlled at 0.05 DEG / day; the mode of cooling by stage is adopted after the seed crystal is in phragmocone; the crystal is in phragmocone until 50 DEG C; cooling rate is kept to 0.05 DEG C / day; at the temperature of 50-35 DEG C, cooling rate is kept to 0.1 DEG C / day; at the temperature of 35 DEG C to room temperature, cooling rate is kept to 0.15 DEG C / day; a crystal rotation mode adopts the following circulation sequence: quickening, positive rotating, slowing down, stalling, quickening, reverse rotating, slowing down and stalling; seed crystal rotates at time interval as follows: 20 seconds, 60 seconds, 20 seconds, 20 seconds, 20 seconds, 60 seconds, 20 seconds and 20 seconds; and the positive rotating rate and the reversal rate are kept to 40-60 turns / minute.

Description

technical field [0001] The present invention relates to crystal growth, in particular to large diameter (>350mm) high quality potassium dihydrogen phosphate (KH 2 PO 4 , referred to as KDP) single crystal cooling growth. Background technique [0002] KDP crystal is an excellent nonlinear optical material, which is mainly used in the second, third and fourth times of laser frequency doubling, especially the high-quality large-size KDP crystal, which has been listed as the only practical material for laser nuclear fusion frequency conversion in the world. , is also a hot topic in international crystal growth research. So far, the traditional cooling method is still used in China to grow large-aperture single crystals. [0003] Large-diameter KDP crystal growth is carried out in a φ1200×1600mm cylindrical stainless steel crystal growth cylinder with a volume of 1.5 tons. growing equipment such as figure 1 As shown, 1 is the crystal growth cylinder, 2 is the cylinder cov...

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Problems solved by technology

Under such control conditions, the seed crystal is cone-shaped and the cooling rate is maintained at 0.2°C / day. If the cooling rate is too large, the accumulation of supersaturation will easily increase, and the phenomenon of "pulling cone" will easily occur, such as figure 2 As shown, it takes a long time for the seed crystal to form a cone, which prolongs the production cycle of the KDP crystal, and white streaks are prone to appear on each crystal face of the crystal, which affects the quality of the finished product

During the long growth process of the crystal transparent layer, water evaporation loss is inevitable, and the cooling rate should be controlled at a low rate. A cooling rate of 0.1°C / day will also cause the accumulation of supersaturation in the solution, destroying the growth of the crystal cone, and With downward growth, the crystal growth surface increases, and a fixed cooling mode cannot be used, resulting in crystal sharpening, such as image 3 shown

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