Thermal and stress distributions in larger sapphire crystals during the cooling process in a Kyropoulos furnace

Chen, Chun Hung; Chen, Jyh Chen; Chiue, Yi Shiuan; Chang, Ching H.; Liu, Che Ming; Chen, Chi Yung

doi:10.1016/j.jcrysgro.2013.04.060

Journal of Crystal Growth

2014

DOI: 10.1016/j.jcrysgro.2013.04.060

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Thermal and stress distributions in larger sapphire crystals during the cooling process in a Kyropoulos furnace

Chun Hung Chen¹,

Jyh Chen Chen²,

Yi Shiuan Chiue³

et al.

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Cited by 8 publications

(1 citation statement)

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“…Because of the irregular shape, high internal stress [9][10] , and easy cracking [11] of the inclined shoulder during crystal processing, the majority of the materials are extracted from the equal-diameter part of the crystal, leaving the shoulder with no practical value. Therefore, the growth of inclined shoulder crystals has the problems of time consumption, material waste, high cost, and thermal field size limitation.…”

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confidence: 99%

Flat Shoulder Congruent Lithium Niobate Crystals Grown by the Czochralski Method

Juan¹,

Dandan²,

Sun³

et al. 2023

Journal of Inorganic Materials

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The shoulder of the crystals grown by the Czochralski method are generally inclined. The quality of the inclined shoulder is poor and the processing is difficult, which result in the low utilization rate of the crystal. This problem can be solved by growing flat shoulder crystals. However, polycrystalline and inclusion defects are easy to occur in the stage of shouldering, so the requirement of thermal field and growth process for the flat shoulder crystal growth is very high. As a multifunctional crystal, lithium niobate crystals have been widely used in the fields of electronics, optical communication, laser, and integrated photonics. Take congruent lithium niobate (CLN) crystal as an example, this study used numerical simulation and experiment method to investigate the thermal field and growth process of flat shoulder crystal growth by the Czochralski method. The result shows that the shape of the solid-liquid interface should be convex toward melt at the stage of shouldering. The temperature gradient near the solid-liquid interface can be reduced by lowering the after-heater position (10 mm) to avoid the formation of polycrystalline. The control of the speed of shouldering is monitored mainly and heating power is adjusted slightly to ensure the trend of shouldering.Increasing the speed at the initial stage of shouldering (ϕ≤30 mm) and decreasing the speed at the middle and later stage of shouldering (ϕ≥35 mm) can shorten the period of shouldering and avoid inclusion. The pulling rate (0-1.5 mm/h) can be changed rapidly (1.5-2 h) without affecting the trend and quality of shouldering by adjusting pulling rate and power with a small amplitude (Δt=10 min, ∆v= 0.2 mm/h). Using the appropriate thermal field and growth process, a series of 3-inch (1 inch=25.4 mm) flat shoulder CLN crystals with good optical homogeneity have been grown.

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mentioning

confidence: 99%

Flat Shoulder Congruent Lithium Niobate Crystals Grown by the Czochralski Method

Juan¹,

Dandan²,

Sun³

et al. 2023

Journal of Inorganic Materials

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3D Anisotropic Stress Analysis during Kyropoulos Growth of Sapphire Single Crystal

Zermout

Mokhtari

Nehari

et al. 2019

Crystal Research and Technology

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By using 3D finite element calculations, numerical simulations are performed to predict the thermal field as well as the thermal stress in a c-axis sapphire single crystal grown by Kyropoulos technique. The effects of additional resistive heating (placed under the crucible bottom) and crystal rotation are investigated and a comparison is made between the isotropic and anisotropic analysis. The anisotropy of the elastic constants and thermal expansion coefficients as well as their temperature dependence are considered in the anisotropy calculations while Young's modulus and the Poisson ratio are used in the isotropic analysis. Thermal stress is found to be smaller in the anisotropy analysis than that in the isotropic analysis and significant differences are found in their respective distribution patterns. Additional resistive heating acts to decrease both of the crystal-melt interface convexity and the von Mises stress. In addition, crystal rotation combined with additional resistive heating decreases significantly the thermal stress inside the sapphire crystal and along the melt-crystal interface. Therefore, optimizing the heating conditions and using a suitable crystal rotation rate seem to be favorable to control the growth interface shape and to reduce thermal-stress-related defects during the growth process.

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Numerical investigation of thermal and residual stress of sapphire during c-axis vertical Bridgman growth process considering the solidification history effect

Hwang¹,

Lee

2018

Met. Mater. Int.

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Thermal and stress distributions in larger sapphire crystals during the cooling process in a Kyropoulos furnace

Cited by 8 publications

References 18 publications

Flat Shoulder Congruent Lithium Niobate Crystals Grown by the Czochralski Method

Flat Shoulder Congruent Lithium Niobate Crystals Grown by the Czochralski Method

3D Anisotropic Stress Analysis during Kyropoulos Growth of Sapphire Single Crystal

Numerical investigation of thermal and residual stress of sapphire during c-axis vertical Bridgman growth process considering the solidification history effect

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