| 학회 | 한국재료학회 |
| 학술대회 | 2018년 가을 (11/07 ~ 11/09, 여수 디오션리조트) |
| 권호 | 24권 2호 |
| 발표분야 | 9. 한-일 재료공학 심포지엄(KMST 2018)-오거나이저: 권도균 교수(한국항공대) |
| 제목 | High performance lead-free piezoelectric single crystals: KNN and CTGAS |
| 초록 | For the past 60 years, Pb-based ceramics are the dominant piezoelectric materials in the market owing to their excellent piezoelectric properties. However, due to the toxic nature of Pb, in the recent decade, there is an increasing request to develop high performance Pb-free piezoelectric materials. As a strategy to maximize the piezoelectric performance, the substitution of ceramics by single crystals is desirable. The later, with a well-ordered atomic lattice and therefore a very low defect density, can exhibit superior material properties, such as high thermal stability of structure and piezoelectricity, super-high mechanical quality factor, low dielectric loss, large piezoelectric coefficient, etc. Therefore, the purpose of my research is to develop high-performance novel Pb-free piezoelectric single crystals. My first topic is focused on Ca3Ta(Ga1-xAlx)3Si2O14 (CTGAS) single crystal for HT piezoelectric sensors. I have grown high quality and colorless (impurity-free) single crystals, from CTGS (x=0) to fully substituted CTAS (x=1), by the Czochralski technique. I have found that an oxygen-less atmosphere favors a higher electrical resistivity, with three orders of magnitude higher values than that of reference La3Ta0.5 Ga5.1Al0.4O14(LTGA). I have demonstrated that the resistivity and piezoelectric coefficient d11 enhance significantly with the increase of Al. Consequently, the best performance was obtained for the fully Al-substituted CTAS crystal. Furthermore, in comparison with reference LTGA, CTAS is free from expensive element Ga, and it can be grown using cheaper Pt crucibles. Taking into account all advantages, CTAS single crystal is at present the most promising langasite for HT piezoelectric sensor applications. My second objective is to develop high performance Pb-free K1-x NaxNbO3 (KNN) single crystals. KNN lead-free compounds are being investigated due to their relatively high piezoelectric coefficient and high Curie temperature. They are considered to be potential candidates to replace Pb-based piezoelectric ceramics in various applications. In this work, KNN single crystals were grown by the top-seed solution growth method, and their properties, including crystal structure, optical and ferroelectric properties, were investigated. This work has been partially supported by the Ministry of Education, Culture, Sports, Science and Technology (MEXT) Element Strategy Initiative to Form Core Center of Japan. |
| 저자 | Xiuwei FU1, Encarnación G. VILLORA2, Yuuki KITANAKA1, Yuji NOGUCHI2, Masaru MIYAYAMA3, Kiyoshi SHIMAMURA4, Naoki OHASHI12 |
| 소속 | 1National Institute for Materials Science, 2Japan, 3Department of Applied Chemistry, 4The Univ. of Tokyo |
| 키워드 | Lead-free; single crystal; langasite |
