Direct observation of crystal growth under hydrothermal condition at the step level

2019 Fiscal Year Final Research Report

• Project/Area Number: 17K14112
• Research Category: Grant-in-Aid for Young Scientists (B)
• Allocation Type: Multi-year Fund
• Research Field: Crystal engineering
• Research Institution: Yamaguchi University
• Principal Investigator: Asakawa Harutoshi 山口大学, 大学院創成科学研究科, 助教 (90757337)
• Project Period (FY): 2017-04-01 – 2020-03-31
• Keywords: 水熱合成 / その場観察 / ノルセサイト / 溶液媒介相転移 / 結晶成長 / 圧電材料

Outline of Final Research Achievements

We attempted to establish the crystal growth mechanism of the hydrothermal treatment, using the norsethite of new piezoelectric material. We produced the chamber for the in-situ observation of the hydrothermal treatment. We found the two-step changes in pH during the dissolution of the norsethite at atmospheric pressure. Also, norsethite crystals were, apparently, formed by the solution-mediated transformation. However, we revealed that the norsethite exhibits the thermodynamic stability lower than the witherite, and intrinsically appears by the co-precipitation. In contrast, under hydrothermal conditions the norsethite is more stable than the witherite, and we succeeded in directly observing the solution-mediated transformation of norethite crystals under hydrothermal conditions. We demonstrated that, for the growth of noreshite crystals, the utilization of the solution-mediated transformation under hydrothermal conditions and the addition of the ammonium nitrate are efficient.

Free Research Field

結晶成長学

Academic Significance and Societal Importance of the Research Achievements

水熱合成は多様な材料の合成や鉱床の形成機構と密接に関連があり、結晶成長学、材料化学、無機化学、セラミクス、地球科学など多岐の分野で用いられている。そのため、確立された成長機構は学術的に大きな寄与をもたらす。本成果を応用すれば育成条件の最適化時間を大幅に短縮できるため、本成果は学理の観点だけでなく工業的にも有用である。従来、圧電結晶は融液法により育成されてきたが、本成果により水熱合成が更に普及すれば、1000℃以上低い温度で材料を育成でき、省エネにも貢献する。更に、本成果は二酸化炭素の固定にも有効で、効率よく二酸化炭素を低減でき、温暖化問題にも貢献する。