東京大学工学系研究科総合研究機構
第17回次世代ジルコニアセミナー

Stressing interfaces to change microstructuresor grow nanostructures
Klaus van Benthem
カリフォルニア大学デービス校 材料科学専攻 教授
Atomic-scale defect configurations determine the properties and functionalities of materials. The
application of stresses such as elevated temperature, modified gas phases, or externally applied electricfields can alter interface structures and, therefore, modify microstructures and macroscopic materials
properties.
Using bicrystal experiments we have previously demonstrated that electric fields directed acrossgrain boundary planes can alter the atomic and electronic structures of (100) twist grain boundaries inSrTiO31. Electric fields directed along the interface plane alter the atomic and electronic grain boundary
structures as a function of field strength and proximity to the positive and negative electrodes. EELS
and XPS have revealed field-induced oxygen ion migration along the interface planes2. Electric fields
directed along a 24 tilt grain boundary in SrTiO3 also show a field-induced transition of the grainboundary core structures between the two non-contacting electrodes. Results suggest anisotropic
vacancy migration.
In another project in-situ SEM and TEM experiments have revealed one-directional growth of single
crystalline nickel oxide nanostructures from individual Ni nanoparticles. Nanostructure growth wasdriven by either the application of electric currents or at high temperature in the presence of water vapor.
The application of electrical bias to individual nanoparticles led to dielectric breakdown of native surface
oxides and subsequent unidirectional mass transport due to a combination of electromigration andLudwig-Soret diffusion3. In the presence of water vapor high-aspect ratio growth of NiO from metalparticles was favored on select surfaces with sufficiently high total surface energies4. In-situ highresolution TEM was used to directly observe layer-by-layer growth at the buried NiO/Ni interface.
Individual layers of NiO were observed to grow by disconnection migration along the oxide/metalinterface plane. At interfacial steps oxidation of Ni is governed by oxygen vacancy migration along theinterface plane. The junction between the oxide/metal interface and the gas phase serves as nucleationsite. The results demonstrate terrace-ledge-kink crystal growth for reactive crystal growth processes atinternal heterophase interfaces5.
The presented results were enabled by financial support from the US National Science Foundation
under award DMR-1836571.
1.
Hughes, L. A., Marple, M. & van Benthem, K. Electrostatic fields control grain boundary structure in SrTiO3.
Appl. Phys. Lett. 113, 041604 (2018).
2.
Qu, B. et al. Defect redistribution along grain boundaries in SrTiO3 by externally applied electric fields. Journalof the European Ceramic Society 43, 1625–1632 (2023).
3.
Rufner, J. F. et al. Local Current-Activated Growth of Individual Nanostructures with High Aspect Ratios.
Materials Research Letters 2, 10–15 (2013).
4.
Qu, B. & van Benthem, K. In situ anisotropic NiO nanostructure growth at high temperature and under watervapor. J Am Ceram Soc. 105, 2454–2464 (2022).
5.
Qu, B. & van Benthem, K. In-situ anisotropic growth of nickel oxide nanostructures through layer-by-layer metaloxidation. Scripta Materialia 214, 114660 (2022).

日時：2024 年 1 月24日（水）14:00～15:30 ハイブリッド開催
主催: 東京大学「次世代ジルコニア創出」社会連携講座
問合せ先：ngzirconia@gmail.com