title: Nanosize effects assisted synthesis of the high pressure metastable phase in ZrO2.
abstract: The size effects on the high pressure behaviors of monoclinic (MI) ZrO2 nanoparticles were studied using in situ high pressure synchrotron X-ray diffraction (XRD) and X-ray absorption spectroscopy (XAS). A size-dependent phase transition behavior under high pressure was found in nanoscale ZrO2. The normal phase transition sequence of MI-orthorhombic I (OI)-orthorhombic II (OII) occurs in 100-300 nm ZrO2 nanoparticles, while only the transition of MI-OI exists in ultrafine ∼5 nm ZrO2 nanoparticles up to the highest experimental pressure of ∼52 GPa. This indicates that the size effects preclude the transition from the OI to the OII phase in ∼5 nm nanoparticles. Upon decompression, the OII and OI phases are retained down to ambient pressure, respectively. This is the first observation of the pure OI phase ZrO2 under ambient conditions. The bulk moduli of the MI ZrO2 nanoparticles were determined to be B0 = 192 (7) GPa for the 100-300 nm nanoparticles and B0 = 218 (12) GPa for the ∼5 nm nanoparticles. We suggest that the significant high surface energy precludes the transition from the OI to the OII phase and the nanosize effects enhance the incompressibility in the ultrafine ZrO2 nanoparticles (∼5 nm). Our study indicates that this is a potential way of preparing novel nanomaterials with high pressure structures using nanosize effects.
authors.affiliation: State Key Laboratory of Superhard Materials, Jilin University, Changchun 130012, P.R. China. liubb@jlu.edu.cn.
authors.forename: Quanjun
authors.initials: Q
authors.lastname: Li
authors.affiliation: State Key Laboratory of Superhard Materials, Jilin University, Changchun 130012, P.R. China. liubb@jlu.edu.cn.
authors.forename: Huafang
authors.initials: H
authors.lastname: Zhang
authors.affiliation: State Key Laboratory of Superhard Materials, Jilin University, Changchun 130012, P.R. China. liubb@jlu.edu.cn.
authors.forename: Ran
authors.initials: R
authors.lastname: Liu
authors.affiliation: State Key Laboratory of Superhard Materials, Jilin University, Changchun 130012, P.R. China. liubb@jlu.edu.cn.
authors.forename: Bo
authors.initials: B
authors.lastname: Liu
authors.affiliation: State Key Laboratory of Superhard Materials, Jilin University, Changchun 130012, P.R. China. liubb@jlu.edu.cn.
authors.forename: Dongmei
authors.initials: D
authors.lastname: Li
authors.affiliation: Beijing Synchrotron Radiation Facility, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, China.
authors.forename: Lirong
authors.initials: L
authors.lastname: Zheng
authors.affiliation: Beijing Synchrotron Radiation Facility, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, China.
authors.forename: Jing
authors.initials: J
authors.lastname: Liu
authors.affiliation: State Key Laboratory of Superhard Materials, Jilin University, Changchun 130012, P.R. China. liubb@jlu.edu.cn.
authors.forename: Tian
authors.initials: T
authors.lastname: Cui
authors.affiliation: State Key Laboratory of Superhard Materials, Jilin University, Changchun 130012, P.R. China. liubb@jlu.edu.cn.
authors.forename: Bingbing
authors.initials: B
authors.lastname: Liu