XANES, EXAFS and photoluminescence investigations on the amorphous Eu:HfO2

Abstract

We report detailed investigations on the local electronic/atomic structure and photoluminescence properties of chemically synthesized Eu:HfO2 powders. X-ray diffraction (XRD), X-ray absorption near edge structure (XANES), extended X-ray absorption fine structure (EXAFS) and photoluminescence (PL) measurements were performed to analyze the crystal structure, local atomic/electronic structure and luminescence properties of the samples. No crystalline phases were detected with Cu K alpha (lambda = 1.5418 angstrom) based XRD; however, local monoclinic structure was confirmed by the Hf L-edge XANES and EXAFS. O K-edge XANES spectral features could be deconvoluted with doublets and triplets in e(g) and t(2g) orbitals, respectively, which ascribed to the local monoclinic structure for all of the samples. Eu M-5.4-edge XANES confirmed the pre-dominancy of Eu3+ ions in the HfO2 samples with a fractional amount of Eu2+ ions. PL spectra revealed the electric dipole allowed (D-5(0)-F-7(0.2,4)) emission properties of Eu:HfO2 samples, The orange-red emission is ascribed to the Eu interstitial/surface segregation induced defects. (C) 2016 Published by Elsevier B.V.