A thermal insulation structure with adjustable axial temperature gradient applied to the growth of sapphire single crystal by foaming method

Abstract

The invention provides an axial temperature gradient-adjustable insulation structure applied to growth of sapphire single crystals by a Kyropoulos method. The insulation structure is arranged in a stainless steel bucket; metal sheets made of tungsten or molybdenum are adopted as heat shields; the heat shields comprise a horizontal heat shield, an oblique heat shield and a vertical heat shield; gaps among the shields are vertically supported by molybdenum strips at intervals; inner and outer filling regions filled with hollow blisters are spaced through the molybdenum strips between the stainless steel bucket and the vertical heat shield; the inner filling region is filled up with ZrO2 hollow blisters; the outer filling region is filled with the ZrO2 hollow blisters or Al2O3 hollow blisters. According to the insulation structure, the axial temperature gradient distribution in a furnace is adjusted by adjusting the height of the outer filling region; the position and the range of a meltback region for crystal growth are adjusted, so that the crystal surface temperature distribution is more gentle, the probability of crystal cracking caused by excessively high heat stress is reduced, the formation of a convex liquid-solid interface in a crystal growth process is facilitated, and the crystal quality is improved.

Description

technical field [0001] The invention provides a thermal insulation structure with adjustable axial temperature gradient in a crystal growth furnace, in particular to a sapphire (α-Al 2 o 3 single crystal) high temperature heat insulation structure. Background technique [0002] α-Al 2 o 3 Single crystal, also known as sapphire, is a simple coordination oxide crystal. Sapphire single crystal has excellent optical and mechanical properties, stable chemical properties, and is widely used in infrared military devices, satellite space technology, and high-intensity laser window materials; its unique lattice structure and good thermal stability make sapphire Single crystal has become an ideal substrate material for GaN light-emitting diodes. [0003] The melting temperature of sapphire crystal is about 2050°C. The Kyropoulos method is one of the most important growth methods at present, and a large number of thermal insulation heat shields are required in the sapphire crystal...

AI Technical Summary

Problems solved by technology

Metal iridium has softened and deformed at 2450°C, and is expensive, so it is not commonly used as an insulation material for large-size crystal growth; the melting point of graphite is above 3800°C, but it is easy to volatilize a large amount of carbon under high temperature conditions, polluting the growth environment; Although the softening temperature of zirconia and alumina ceramics is above 2700°C, they are heavy and easy to crack at high temperatures. If they are designed as large insulation layers, they are not easy to transport and disassemble. They should only be used in small quantities and designed into special structures.

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