Surface structures of cerium oxide nanocrystalline particles from the size dependence of the lattice parameters

Abstract

Cerium oxide nanocrystalline particles are synthesized and monodispersed in the size range from 2 to 8nm in diameter. The dependence of the lattice parameters on particle size is obtained by x-ray and electron diffraction analyses. The size dependence well coincides with the estimation based on the assumption that the surface is composed of one layer of Ce2O3 and the inside consists of CeO2. The effect of particle size on lattice parameters is discussed from the differences in the fabrication method and the surface structure.

Electrical conductivity of Gd-doped ceria with nano-sized grain

“…The 0.2 M Ce(NO 3 ) 3 and Gd(NO 3 ) 3 solutions were mixed at a molar ratio of Ce : Gd = 4 : 1. The glycine (NH 2 CH 2 COOH, Wako Pure Chemical Industries Ltd., Japan) was added into the mixed solution at a molar ratio of glycine : NO 3 − = 5 : 9 which is stoichiometric ratio for the reaction between glycine and nitrate as expressed by Eqs.…”

“…RESULTS AND DISCUSSION 3.1 Microstructure of the sintered GDC Figure 2(a) shows the microstructure for the GDC sintered at 900 ºC for 5 min using the SPS process with a relative density of 96.2 % based on the theoretical density of 7.238 g/cm 3 . The grain size of the GDC sintered using the SPS process was about 20 nm.…”

“…Recently, the influences of grain size on the material properties of ceria have been reported. The ionic conductivity [1,2] and the lattice parameter [3] for the doped or undoped ceria varied with the grain size. The variation of the ionic conductivity with the grain size was demonstrated based on the curvature of grain in a literature [4].…”

Thickness Effect on Fluctuation of Electron States in Thin Film and Implications for Lattice Constant Change Due to Size Reduction

“…When either expansion or contraction is observed, some materials show only contraction or expansion, and some materials show both expansion and contraction, measured relative to the corresponding parameters in the bulk state. Expansion of the lattice parameter is generally observed in oxides such as CeO 2 [4][5][6], Fe 2 O 3 [7], MgO [8], TiO 2 (rutile) [9], ZrO 2 [10], BaTiO 3 [11], cubic PbTiO 3 [12], and BiFeO 3 [13]. In contrast, contraction in the lattice parameter, is observed in most metals, such as Au [14][15][16], Ag [17][18][19][20], Sn [21], Bi [21,22], Pt [15,23], Si [24], Cu [25], Ni [25], Pd [26,27], ZnS and CdSe [28,29].…”

“…Tsunekawa,et al in [5,6,30] proposed that the lattice parameter expansion in CeO 2 is caused by the presence of surface stable Ce 3+ anion vacancy sites within the surface layer at low nanoparticle dimensions. Shin,et al in [31] have proposed that the lattice dilatation in Sn nanowire is caused by strong anisotropy on the surface stress.…”