Eu-Doped Cerium Oxide Nanoparticles Studied by Positron Annihilation

• Authors: A. Thorat , T. Ghoshal , M. Morris , P. Nambissan
• Languages of publication: EN

Abstracts

EN

The defect characteristics of cerium oxide (CeO_2) nanoparticles prepared through a solvothermal process and doped by europium to different concentrations ([Eu] = 0, 0.1, 0.5, 1, ..., 50 wt%) were studied by positron lifetime and coincidence Doppler broadening measurements. The particle sizes estimated from X-ray diffraction showed a reducing trend with increasing doping concentration except an increase during [Eu] = 0.1-1 wt%. The latter effect is attributed to the reduction of Ce^{4+} ions to Ce^{3+} resulting into the release of vacancies and formation of Ce^{3+}-vacancy associates. The lattice parameter increased with the decrease in particle size. Quantum confinement effects were observed in optical absorption studies as increase of band gap in particles of sizes below 7-8 nm. The vacancy-type defects were investigated by positrons. A lifetime of 176 ± 4 ps less than 187-189 ps reported for positrons in bulk CeO_2 reveals trapping of positrons in vacancy-type defects within the nanocrystallites. The defect-specific positron lifetime is admixed with that at the crystallite surfaces and it increased due to vacancy agglomeration at higher doping concentrations. Coincidence Doppler broadening studies indicated positron annihilation in defects surrounded by oxygen ions and the S-W plot showed the effect of quantum confinement through a peak-like kink or shoulder in the plot. Optical absorption studies have supported this observation.

Keywords

EN

61.46.Df; 78.20.Ci; 61.72.jd; 12.38.Aw; 78.70.Bj

Discipline

• 78.70.Bj: Positron annihilation(for positron states, see 71.60.+z in electronic structure of bulk materials; for positronium chemistry, see 82.30.Gg in physical chemistry and chemical physics)
• 12.38.Aw: General properties of QCD (dynamics, confinement, etc.)
• 78.20.Ci: Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
• 61.72.jd: Vacancies
• 61.46.Df: Structure of nanocrystals and nanoparticles ("colloidal" quantum dots but not gate-isolated embedded quantum dots)

• Publisher: Institute of Physics, Polish Academy of Sciences
• Journal: Acta Physica Polonica A
• Year: 2014
• Volume: 125
• Issue: 3
• Pages: 756-759

Dates

published

2014-03

Contributors

author

A. Thorat

• Materials Research Group, Department of Chemistry and Tyndall National Institute University College Cork, Cork, Ireland
• Centre for Research on Adaptive Nanostructures and Nanodevices, Trinity College Dublin, Dublin, Ireland

author

T. Ghoshal

• Materials Research Group, Department of Chemistry and Tyndall National Institute University College Cork, Cork, Ireland
• Centre for Research on Adaptive Nanostructures and Nanodevices, Trinity College Dublin, Dublin, Ireland

author

M. Morris

• Materials Research Group, Department of Chemistry and Tyndall National Institute University College Cork, Cork, Ireland
• Centre for Research on Adaptive Nanostructures and Nanodevices, Trinity College Dublin, Dublin, Ireland

author

P. Nambissan

• Applied Nuclear Physics Division, Saha Institute of Nuclear Physics, Kolkata 700064, India

References

• [1] L. Chen, P. Fleming, V. Morris, J.D. Holmes, M.A. Morris, J. Phys. Chem. C 114, 12909 (2010), doi:10.1021/jp1031465
• [2] S. Tsunekawa, J.-T. Wang, Y. Kawazoe, J. Alloys Comp. 408-412, 1145 (2006), doi:10.1016/j.jallcom.2004.12.140
• [3] P.M.G. Nambissan, in: Nanotechnology: Synthesis and Characterization, Vol. 2, Eds. Shishir Sinha, N.K. Navani, J.N. Govil, Studium Press LLC, Houston 2013, p. 455
• [4] P.M.G. Nambissan, J. Phys., Conf. Series 443, 012040 (2013), doi:10.1088/1742-6596/443/1/012040
• [5] J.V. Olsen, P. Kirkegaard, N.J. Pedersen, M. Eldrup, Phys. Status Solidi C 4, 4004 (2007), doi:10.1002/pssc.200675868
• [6] A. Chatterjee, K. Ramachandran, A. Kumar, A. Behere, http://www.tifr.res.in/~pell/lamps.html Linux Advanced Multi Parameter System (2013)
• [7] A.L. Patterson, Phys. Rev. 56, 978 (1939), doi:10.1103/PhysRev.56.978
• [8] A.V. Thorat, T. Ghoshal, J. Holmes, P.M.G. Nambissan, M.A. Morris, Nanoscale 6, 608 (2014), doi:10.1039/c3nr03936f
• [9] S.J. Chang, M. Li, Q. Hua, L.J. Zhang, Y.S. Ma, B.J. Ye, W.X. Huang, J. Catalysis 293, 195 (2012), doi:10.1016/j.jcat.2012.06.025
• [10] A. Sachdeva, S.V. Chavan, A. Goswami, A.K. Tyagi, P.K. Pujari, J. Solid State Chem. 178, 2062 (2005), doi:10.1016/j.jssc.2005.04.016
• [11] A. Uedono, K. Shimoyama, M. Kiyohara, K. Yamabe, J. Appl. Phys. 94, 5193 (2003), doi:10.1063/1.1606112
• [12] S. Deshpande, S. Patil, S.V.N.T. Kuchibhatla, S. Seal, Appl. Phys. Lett. 87, 133113 (2005), doi:10.1063/1.2061873

Identifiers

DOI

10.12693/APhysPolA.125.756