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1993 Fiscal Year Final Research Report Summary

Material strength study on cracking of oxide bulk single crystals for optelectronic use

Research Project

Project/Area Number 04650089
Research Category

Grant-in-Aid for General Scientific Research (C)

Allocation TypeSingle-year Grants
Research Field 材料力学
Research InstitutionKYUSHU UNIVERSITY

Principal Investigator

MIYAZAKI Noriyuki  Kyushu University, Department of Chemical Engineering, Associate Professor, 工学部, 助教授 (10166150)

Co-Investigator(Kenkyū-buntansha) IKEDA Toru  Kyushu University, Department of Chemical Engineering, Research Associate, 工学部, 助手 (40243894)
MUNAKATA Tsuyoshi  Kyushu University, Department of Chemical Engineering, Professor, 工学部, 教授 (00037714)
Project Period (FY) 1992 – 1993
KeywordsOxide Single Crystal / Czochralski Growth / Thermal Stress / Finite Element Method / Thermal Expansion Coefficient / Elastic constants / Anisotropy / Cracking
Research Abstract

Oxide single crystals such as LiNbO_3(LN) and LiTaO_3(LT) are used as optelectronic materials. Such bulk single crystals are manufactured by the Czochralski growth method. Macroscopic cracking sometimes occurs during growth process. Such cracking would be caused by thermal stress in a single crystal. In the present study, a finite element computer program was developed for the thermal stress analysis of trigonal single crystals such as LN and LT.A tensor transformation technique was used to obtain the elastic constant matrix and the thermal expansion coefficient vector corresponding to an arbitrary pulling direction, and they are incorporated into the finite element program. Using this program, we analyzed the thermal stress in LN bulk single crystals, which were grown in a pulling apparatus in Institute for Materials Research, Tohoku University. The temperature boundary conditions of the crystals were obtained from the heat conduction analysis of the global system. Thermal stress analyzes were performed for the pulling directions of both the a-axis and the c-axis. The results show that the maximum thermal stress is lower in the c-axis pulling than in the a-axis pulling, which indicates that the a-axis pulling is easier to crack than the c-axis pulling. It is also found that a lower stress region spreads widely in the bulk single crystal pulled in the a-axis direction. This predicts that the a-axis pulling could provide a bulk single crystal of higher quality than the c-axis pulling, if macroscopic cracking can be prevented. This prediction was verified by observing microscopic defects in a single crystal obtained by the a-axis pulling.
In order to study the cracking of LN single crystals quantitatively, thermal shock experiments were carried out using circular disk speciments. The experimental results show that the cracking mainly occurs at the cleavage planes, which indicates that the stresses normal to the cleavage planes would induce the cracking.

  • Research Products

    (6 results)

All Other

All Publications (6 results)

  • [Publications] 宮崎 則幸: "Thermal Stress Analysis of Silicon Bulk Single Crystal during Czochralski Growth" Journal of Crystal Growth. 125. 102-111 (1992)

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] 宮崎 則幸: "バルク単結晶CZ育成過程の熱応力解析(各種単結晶における異方性の効果)" 日本機械学会論文集,A編. 58. 1942-1946 (1992)

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] 宮崎 則幸: "酸化物バルク単結晶CZ育成過程に生じる割れの定量的評価(第1報,熱応力解析プログラムの開発)" 日本機械学会論文集,A編. 59. 2264-2769 (1993)

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] Noriyuki MIYAZAKI: "Thermal Stress Analysis of Silicon Bulk Single Crystal during Czochralski Growth" Journal of Crystal Growth. Vol.125. 102-111 (1992)

    • Description
      「研究成果報告書概要(欧文)」より
  • [Publications] Noriyuki MIYAZAKI: "Thermal Stress Analysis of Bulk Single Crystal during Czochralski Growth(Anisotropic Effects in Various Single Crystals)" Transactions of Japan Society of Mechanical Engineers. Series A, Vol.58. 1942-1946 (1992)

    • Description
      「研究成果報告書概要(欧文)」より
  • [Publications] Noriyuki MIYAZAKI: "Quantitative Assessment of Cracking in Oxide Bulk Single Crystals during Czochralski Growth (1st Report, Development of Computer Program for Thermal Stress Analyzes)" Transactions of Japan Society of Mechanical Engineers. Series A, Vol.59. 2764-2769 (1993)

    • Description
      「研究成果報告書概要(欧文)」より

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Published: 1995-03-27  

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