Preparation method of composition-controlled directional crystallization of near-stoichiometric lithium niobate crystals

Abstract

The invention discloses a method for preparing a composition-controllable directional crystallization of lithium niobate crystals with a near-stoichiometric ratio, so that a low-temperature zone, a high-temperature zone, a temperature gradient zone and a heat preservation zone are successively formed in the hearth of a single crystal furnace, and the crucible is successively changed from four to four temperature zone through. The specific steps include in turn, 1) Pre-crystallization material preparation: prepare two mixtures AB formed by Li2CO3 and Nb2O5, wherein the Li / Nb molar ratio in the mixture A is 1:1, and the Li / Nb molar ratio in the mixture B is between Between 1:1 and 58.5 / 41.5; 2) Furnace loading: Lithium niobate seed crystal is placed in the crucible seed crystal groove, pre-crystallization material B is placed in the shoulder of the crucible, and pre-crystallization material A is placed in the equal width part of the crucible; 3) chemical material; 4) seeding; 5) shouldering; 6) equal width growth; 7) finishing; 8) annealing and cooling. The preparation of N‑SLN crystals by this method has the outstanding advantages of large size, high quality, uniform Li content, low energy consumption, and high repeatability, and is easy to realize large-scale production.

Description

technical field [0001] The invention relates to near-stoichiometric lithium niobate (N-SLN for short) crystals, in particular to a method for preparing N-SLN crystals with controllable directional crystallization, belonging to the technical field of crystal growth. Background technique [0002] Lithium niobate crystal is a multifunctional crystal material integrating piezoelectric, ferroelectric, pyroelectric, nonlinear, electro-optic, photoelastic, photorefractive and other functions. At present, it has been used in infrared detectors, laser modulators, optical communication modulators, optical switches, optical parametric oscillations, integrated optical components, high-frequency broadband filters, narrow-band filters, high-frequency high-temperature transducers, microacoustic devices, lasers, etc. Frequency multipliers, holographic storage, and optical waveguides have been widely used in practical applications. However, although the commonly used lithium niobate (CLN) c...

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Problems solved by technology

Although this method is currently the best method for growing large-sized N-SLN crystals, it still has the following disadvantages: First, because the inner and outer crucibles are only connected by small holes at the bottom, the melts in the inner and outer crucibles cannot be fully mixed, resulting in crystal composition It is not completely uniform; second, the melt flowing from the outer crucible to the inner crucible carries heat and mass, and its symmetry is poor, which will increase the instability of the temperature field of the inner crucible; third, it is difficult for the continuous feeding device to accurately replenish the required feedstock, which is affected by fluctuations in feedstock particle size, uniformity, and actual growth rate

Although the continuous feeding double crucible method has been invented for more than 20 years, it still remains in the laboratory stage and has not achieved large-scale industrial production

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