Method and device for near stoichiometric lithium niobate single crystal growth

Abstract

The invention provides a method and a device for near stoichiometric lithium niobate single crystal growth. The method and the device are main suitable for Czochralski method-based growth of near stoichiometric lithium niobate single crystals having uniform components and relate to the field of crystal growth. The method is characterized in that liquid synthetic polycrystalline raw materials are prepared into near stoichiometric lithium niobate single crystals having large sizes and high quality in a N2-CO2 weak-oxidizing protective atmosphere through a suspension-type three-crucible automatic continuous charging system. The method and the device have the advantages that polycrystalline raw material components are uniform; a Li2O volatilization amount is low; automatic continuous charging is realized; melting efficiency is high; and a temperature fluctuation of a crystal growth zone is small.

Description

technical field [0001] The invention relates to the field of crystal growth, in particular to a method for preparing a near-stoichiometric lithium niobate single crystal and a device used therefor. Background technique [0002] Lithium niobate (LiNbO 3 , LN) crystal is an excellent multifunctional crystal, which has excellent piezoelectric properties, nonlinear optical properties, electro-optic and photorefractive properties, etc. Large-sized LN crystals can be grown by pulling method, and LN crystals have good thermal stability, chemical stability and mechanical stability. Based on the above advantages, LN crystals are widely used in nonlinear optics, optoelectronics, communications and optical storage. The usual lithium niobate crystals are grown by the pulling method from the homogeneous eutectic composition, and the Li / Nb molar ratio is 48.4 / 51.6 instead of the stoichiometric ratio. The absence of Li ions causes a large number of vacancy defects in the crystal, which ...

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Problems solved by technology

However, due to the high melting point of LN crystals (generally at 1200-1300°C), if the reaction pre-synthesis is not performed in advance, at this temperature, it is easy to cause volatilization of oxides and carbonates, which makes the melt composition deviate; moreover, the raw materials Middle Li 2 CO 3 Excessive amount, cannot be completely decomposed during the melting process of raw materials, so a large amount of gas will be generated during the crystal growth process, and bubbles will be formed inside the crystal, affecting the quality of the crystal

[0011] Another Chinese patent application No. 200410024543.3 discloses a technology that improves the double crucible method. During the crystal growth process, the crucible is divided into two regions by a movable upper closed noble metal cylinder, It solves the problems of low melting efficiency of the double-crucible device in the prior art, uneven melting in the melting zone during continuous feeding, easy generation of floating crystals and volatilization of lithium oxide, etc.

However, in the growth process of this kind of high-temperature volatile crystals, it is found that the volatilized components in the high-temperature melt are quickly deposited on the heat preservation cover, rather than existing in the sealed system in the form of gas, so the sealed system cannot It has the effect of inhibiting the volatilization of components after reaching the saturated vapor pressure

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