title: Atomistic mechanisms of nonstoichiometry-induced twin boundary structural transformation in titanium dioxide.
abstract: Grain boundary (GB) phase transformations often occur in polycrystalline materials while exposed to external stimuli and are universally implicated in substantially affecting their properties, yet atomic-scale knowledge on the transformation process is far from developed. In particular, whether GBs loaded with defects due to treatments can still be conventionally considered as disordered areas with kinetically trapped structure or turn ordered is debated. Here we combine advanced electron microscopy, spectroscopy and first-principles calculations to probe individual TiO2 GB subject to different atmosphere, and to demonstrate that stimulated structural defects can self-assemble at GB, forming an ordered structure, which results in GB nonstoichiometry and structural transformations at the atomic scale. Such structural transformation is accompanied with electronic transition at GB. The three-dimensional transformations afford new perspectives on the structural defects at GBs and on the development of strategies to manipulate practically significant GB transformations.
authors.affiliation: Institute of Engineering Innovation, The University of Tokyo, 2-11-16, Yayoi, Bunkyo-ku, Tokyo 113-8656, Japan.
authors.forename: Rong
authors.initials: R
authors.lastname: Sun
authors.affiliation: Advanced Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577, Japan.
authors.forename: Zhongchang
authors.initials: Z
authors.lastname: Wang
authors.affiliation: Advanced Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577, Japan.
authors.forename: Mitsuhiro
authors.initials: M
authors.lastname: Saito
authors.affiliation: Institute of Engineering Innovation, The University of Tokyo, 2-11-16, Yayoi, Bunkyo-ku, Tokyo 113-8656, Japan.
authors.forename: Naoya
authors.initials: N
authors.lastname: Shibata
authors.affiliation: 1] Institute of Engineering Innovation, The University of Tokyo, 2-11-16, Yayoi, Bunkyo-ku, Tokyo 113-8656, Japan [2] Advanced Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577, Japan [3] Nanostructures Research Laboratory, Japan Fine Ceramics Center, 2-4-1 Mutsuno, Atsuta, Nagoya 456-8587, Japan.
authors.forename: Yuichi
authors.initials: Y
authors.lastname: Ikuhara