Interaction of lattice defects and clarification of conduction mechanism in Oxide Ion Conductors

Research Project

Project/Area Number	60470079
Research Category	Grant-in-Aid for General Scientific Research (B)
Allocation Type	Single-year Grants
Research Field	工業物理化学
Research Institution	University of Tokyo
Principal Investigator	FUEKI Kazuo Professor, Department of Industrial Chemistry, 工学部, 教授 (80010750)
Co-Investigator(Kenkyū-buntansha)	KISHIO Kohji Research Associate, Department of Industrial Chemistry, 工学部, 助手 (50143392) KITAZAWA Koichi Associate Professor, Department of Industrial Chemistry, 工学部, 助教授 (90011189)
Project Period (FY)	1985 – 1986
Project Status	Completed (Fiscal Year 1986)
Budget Amount *help	¥4,700,000 (Direct Cost: ¥4,700,000) Fiscal Year 1986: ¥1,700,000 (Direct Cost: ¥1,700,000) Fiscal Year 1985: ¥3,000,000 (Direct Cost: ¥3,000,000)
Keywords	Oxide Ion Conductors / Defect Equilibrium / Defect Interaction / Conductivity Nuclear Magnetic Resonance / Secondary Ion Mass Spectrometry / 2次イオン質量分析 / プロトン導電体
Research Abstract	The purpose of this investigation was to clarify the effect of interaction of lattice defects on their motion in oxide ion conductors from both microscopical and macroscopical view points and to search for guiding principles for the development of good oxide ion conductors. Oxide ion conductivity in perovskite-type <La_(1-x)> <Ca_x> <AlO_(3-(delta))> was microscopically stud ied through <^(27)Al> NMR relaxation time and absorption spectrum measurement and also macroscopically through conductivity as well as isotopic diffusion measurements using SIMS. From conductivity study it was concluded that the transport of oxide ions could be interpreted to occur via relatively free vacancies without interactions with other point defects. SIMS measurement in this oxide system was found to be strongly affected by a surface exchange reaction of the oxygen isotope at the gas-solid interface. NMR relaxation study resulted in smaller activation energy for oxide ion motion than that determined from resistivity, indicating the NMR method reflects a microscopical local motion. It was shown that <^(27)Al> NMR spectrum of single crystal specimen was effective in elucidating local electric symmetry around the probing nuclei in the crystal. <^(17)O> NMR and conductivity measurements were performed on stabilized <Bi_2O_3> which has a pseudo-fluorite structure and known to display the highest oxide ion conductivity. In this system, it was found that the activation energy for oxide motion increases with impurity doping and the lowering of the resistivity could be interpreted in terms of the interaction between the point defects. Solubility of hydrogen into proton conducting oxide <SrCe_(0.95)> <Yb_(0.05)> <O_(3-(delta))> annealed in water vapour as well as its ionic conductivity were investigated. The mechanism of protonic conduction in this oxide system was discussed from the view point of defect chemistry.