title: Electronic structure study of Ce1-xAxO2 (A = Zr & Hf) nanoparticles: NEXAFS and EXAFS investigations.
abstract: Single phase nanoparticles (NPs) of CeO2, Ce0.5Zr0.5O2, Ce0.5Hf0.5O2 and Ce0.5Hf0.25Zr0.25O2 were successfully synthesized by co-precipitation method at constant pH and temperature. The X-ray diffraction results revealed that the additive atoms did not segregate to form secondary phases but led to grain size variation in the NPs. The 10 Dq values in the near edge X-ray absorption fine structure (NEXAFS) spectra at the O K-edge did not vary in the same way as the average grain size was changed for the doped CeO2 NPs. The deconvolution of Ce M5-edge and detailed analysis of O K pre-edge peak have shown the higher Ce(+3)/(Ce(+3) + Ce(+4)) ratio in the Zr- and Hf-doped samples. The local atomic structure around the Ce, Zr and Hf atoms was investigated using extended X-ray absorption fine structure (EXAFS) spectroscopy at Ce K-edge, Zr K-edge and Hf L3-edge, respectively, and the EXAFS data were fitted with the theoretical calculations. The 4f occupancy, Ce(+3)/(Ce(+3) + Ce(+4)) ratio of Ce ions, coordination number of Ce and Ce-Ce/Ce-O bond distances were sensitive to the additive atoms but not explicitly changed according to the grain size variation in the NPs.
authors.affiliation: Pohang Accelerator Laboratory, POSTECH, Pohang - 790-784, South Korea. adityaiuac@gmail.com shj001@postech.ac.kr.
authors.forename: Aditya
authors.initials: A
authors.lastname: Sharma
authors.forename: Mayora
authors.initials: M
authors.lastname: Varshney
authors.forename: Hyun-Joon
authors.initials: HJ
authors.lastname: Shin
authors.forename: Yong Jun
authors.initials: YJ
authors.lastname: Park
authors.forename: Min-Gyu
authors.initials: MG
authors.lastname: Kim
authors.forename: Tae-Kyun
authors.initials: TK
authors.lastname: Ha
authors.forename: Keun Hwa
authors.initials: KH
authors.lastname: Chae
authors.forename: Sanjeev
authors.initials: S
authors.lastname: Gautam