title: Unusual compression behavior of nanocrystalline CeO₂.
abstract: The x-ray diffraction study of 12 nm CeO2 was carried out up to ~40 GPa using an angle dispersive synchrotron-radiation in a diamond-anvil cell with different pressure transmitting medium (PTM) (4:1 methanol: ethanol mixture, silicone oil and none) at room temperature. While the cubic fluorite-type structure CeO2 was retained to the highest pressure, there is progressive broadening and intensity reduction of the reflections with increasing pressure. At pressures above 12 GPa, an unusual change in the compression curve was detected in all experiments. Significantly, apparent negative volume compressibility was observed at P = 18-27 GPa with silicone oil as PTM, however it was not detected in other circumstances. The expansion of the unit cell volume of cubic CeO2 was about 1% at pressures of 15-27 GPa. To explain this abnormal phenomenon, a dual structure model (hard amorphous shell and relatively soft crystalline core) has been proposed.
authors.affiliation: Institute of Atomic and Molecular Physics, Sichuan University, Chengdu 610065, China.
authors.forename: Qiming
authors.initials: Q
authors.lastname: Wang
authors.affiliation: 1] Institute of Atomic and Molecular Physics, Sichuan University, Chengdu 610065, China [2] Institute of Fluid Physics and National Key Laboratory of Shockwave and Detonation Physics, China Academy of Engineering Physics, Mianyang 621900, China.
authors.forename: Duanwei
authors.initials: D
authors.lastname: He
authors.affiliation: Institute of Atomic and Molecular Physics, Sichuan University, Chengdu 610065, China.
authors.forename: Fang
authors.initials: F
authors.lastname: Peng
authors.affiliation: Institute of Atomic and Molecular Physics, Sichuan University, Chengdu 610065, China.
authors.forename: Li
authors.initials: L
authors.lastname: Lei
authors.affiliation: Institute of Atomic and Molecular Physics, Sichuan University, Chengdu 610065, China.
authors.forename: Pingping
authors.initials: P
authors.lastname: Liu
authors.affiliation: Institute of Atomic and Molecular Physics, Sichuan University, Chengdu 610065, China.
authors.forename: Shuai
authors.initials: S
authors.lastname: Yin
authors.affiliation: Institute of Atomic and Molecular Physics, Sichuan University, Chengdu 610065, China.
authors.forename: Pei
authors.initials: P
authors.lastname: Wang
authors.affiliation: Institute of Atomic and Molecular Physics, Sichuan University, Chengdu 610065, China.
authors.forename: Chao
authors.initials: C
authors.lastname: Xu
authors.affiliation: Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, China.
authors.forename: Jing
authors.initials: J
authors.lastname: Liu
mesh_terms: D002563:Cerium / Q000737:chemistry*; D053758:Nanoparticles / Q000737:chemistry*; D036103:Nanotechnology; D011312:Pressure; D013059:Spectrum Analysis, Raman; D017356:Synchrotrons; D014961:X-Ray Diffraction
chemical_list: D002563:Cerium; C030583:ceric oxide