Production of crystallographically-aligned piezoelectric thinfilm by nucleation-controlled hydrothermal synthesis and its evaluation

2021 Fiscal Year Final Research Report

• Project/Area Number: 19K04108
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 18020:Manufacturing and production engineering-related
• Research Institution: Tokyo Metropolitan University
• Principal Investigator: Moronuki Nobuyuki 東京都立大学, システムデザイン研究科, 教授 (90166463)
• Co-Investigator(Kenkyū-buntansha): 金子 新 東京都立大学, システムデザイン研究科, 教授 (30347273)
• Project Period (FY): 2019-04-01 – 2022-03-31
• Keywords: 水熱合成 / 二酸化チタン / チタン酸バリウム / 圧電材料 / 結晶配向 / 結晶成長

Outline of Final Research Achievements

This study aims to develop a process to produce piezoelectric devices that consist of an array of single crystal barium titanate rods vertically oriented on a substrate. The process is divided into two step hydrothermal synthesis. At the first step, array of titanium dioxide rods was produced on a fluorine-doped tin oxide substrate using lattice constant similarity to control the nucleation, and in the second step the titanium dioxide rods were converted into barium titanate rods. It was found that hydrochloric acid concentration at the first step is an important factor because it has strong effect on the spacing between the rods and then the conversion rate to barium titanate. Typical rod height was 2 microns after 4 hours synthesis. X ray diffraction results showed strong peak of (110) crystal plane. Piezoelectric characteristic was examined with a hammering test with steel ball dropping. Patterning of the rod array on the substrate was also examined applying lithography.

Free Research Field

微細加工と表面機能

Academic Significance and Societal Importance of the Research Achievements

圧電材料を用いて環境中の微小振動を電気エネルギに変換することができ，センサネットワーク等の電源とすることでバッテリーや配線の削減，ひいては炭酸ガス排出の削減が検討されている．チタン酸バリウムは従来の圧電素子（PZT）のように鉛を含まない圧電材料として期待されているものの，その効率を向上するために単結晶で配向した構造は必ずしも得られていなかった．格子定数が近いフッ化ドープ酸化錫を基板に用いた水熱合成により二酸化チタンの垂直配向構造が得られることはわかっていたが，二段階目の水熱合成を行ってチタン酸バリウムに変換する手法はこれまで明らかにされていなかった．