Preparation of ion conductive thin films in reaction field assisted by some excitation method

• Project/Area Number: 09650815
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Metal making engineering
• Research Institution: Waseda University
• Principal Investigator: FUWA Akio Waseda University, School of Science and Engineering, Professor, 理工学部, 教授 (60139508)
• Co-Investigator(Kenkyū-buntansha): SAITO Nagahiro Japan Science Promotion, Research Fellows, 特別研究員 ; 斎藤 永宏 早稲田大学, 理工学部, 日本学術振興会特別研
• Project Period (FY): 1997 – 1999
• Project Status: Completed (Fiscal Year 1999)
• Budget Amount: ¥3,600,000 (Direct Cost: ¥3,600,000); Fiscal Year 1999: ¥100,000 (Direct Cost: ¥100,000); Fiscal Year 1998: ¥200,000 (Direct Cost: ¥200,000); Fiscal Year 1997: ¥3,300,000 (Direct Cost: ¥3,300,000)
• Keywords: YSZ / MOCVD / Thin films / Crystal structure / 導電率 / 複合反応場 / イオン導電性

Research Abstract

Yttria-Stabilized Zirconia (YSZ) has high potential to be used as an electrolyte of solid-oxide fuel cell (SOFC). However the high generation-efficiency of SOFC has not been yet achieved due to the high internal of bulk electrolyte. The resistance becomes lower with the decrease of electrolyte thickness. The aim of this study is the low-temperature preparation of YSZ thin films by plasma-enhanced metal organic chemical vapor deposition (PEMOCVD). YSZ solid electrolye thin films were prepared from Zr (t-OCィイD24ィエD2HィイD29ィエD2)ィイD24ィエD2, Y (CィイD211ィエD2HィイD219ィエD2OィイD22ィエD2)ィイD23ィエD2 and evaluated the crystallization. The composition of YSZ thin films was controlled by the change of the vapor pressure of precursors and analyzed by XRF. Relationship between the change of Y-concentration in the thin films and the structural characterizations were examined from the measurement of SEM, XRD and conducitivity by complex impedance plot. The effect of the plasma-enhanced reaction was clarified by the comparison of the YSZ thin films prepared by PEMOCVD and thermal MOCVD from the viewpoint of the microscopic structure and the residual carbon. These properties were examined by measurement of SEM and FT-IR spectrum.
In the first year, inductively-coupled RF plasma-enhanced metal organic chemical vapor deposition apparatus was produced. In the second year, YSZ thin films (in the composition range 3.1〜5.1mol% Y) could be prepared. The crystal structure was the mixture of monoclinic and cubic. The conductivity became higher with the increase of Y-content in the thin films. However, the conductivity was lower than bulk materials two digit. In this year, YSZ thin films (in the composition range 3〜12mol% YィイD22ィエD2OィイD23ィエD2) could be prepared. Y/Zr ratio in the YSZ thin films was found to be lower than the Y (CィイD211ィエD2HィイD219ィエD2OィイD22ィエD2)ィイD23ィエD2/Zr(t-OCィイD24ィエD2HィイD29ィエD2)ィイD24ィエD2 raito.These results indicate that the Y is difficult to be solute in the preparation films. The crystal structure of these compositions was cubic by returning predicition of the phase diagram. The surface morphology was denser with the increase of Y-content in the YSZ thin films and by applying the plasma. The residual carbon originated for the C-H bond was decreased by the plasma-enhanced reaction.