Effect of lattice distortion in optical properties of CeO2 nanocrystals on Mn substitution by mechanical alloying

摘要

The present paper exhibits the incorporation of Mn ions within a CeO2 host lattice by mechanical alloying and its implications on modification of optical properties of the Mn-doped CeO2 lattice. The gradual increase of lattice defects within the cubic fluorite-type CeO2 lattice corresponds to the change in optical properties with varying degree of the dopant incorporation, which has been regulated by the duration of the ball milling process. The phase purity and structure/microstructure characteristics of synthesized undoped and Mn-doped CeO2 powder samples have been evaluated using XRD, HRTEM, FTIR, Raman and photoluminescence (PL) spectroscopy. The Rietveld refinement of XRD data reveals the detailed structural distortion and microstructure of all milled samples. HRTEM analysis reveals the structure, microstructure, presence of twin faults and yielding elongation or Luders strains in the 6 h ball milled Mn-doped CeO2 sample. Both XRD and HRTEM measurements ascertain the average size of CeO2 nanocrystallites/particles are close to 10 nm. Band gap energies of all milled samples obtained from UV -vis absorption spectra reveal a blue shift at the initial stage of milling up to 2 h (similar to 2.4% Mn doping) and then red-shifted up to 6 h of milling (5 mol% Mn doping). Variations of structural defects and luminescence efficiency of all samples in the course of milling have been measured by analyzing respective PL emission spectrum. The 5 mol% Mn-doped 6 h milled sample shows 74% photodegradation efficiency of Rhodamine B (RhB) under visible light irradiation within 300min. (C) 2019 Elsevier B.V. All rights reserved.