Blue-silica by Eu<sup>2+</sup>-activator occupied in interstitial sites

Donghyeon Kim, Yoeng Hun Jin, Ki Wan Jeon, Sungyun Kim, Seung Joo Kim, Oc Hee Han, Dong Seo, Jung Chul Park

Research output: Contribution to journalArticle

18 Scopus citations

Abstract

A blue-emitting SiO<inf>2</inf>:Eu<sup>2+</sup> compound has been successfully synthesized and characterized. The PL intensity of SiO<inf>2</inf>:Eu<inf>0.002</inf><sup>2+</sup> compound is about 24 times higher than that of the O-defective SiO<inf>2</inf> compound (without activators), which emits blue light. The valence state of the Eu ions responsible for the highly enhanced blue emission was determined to be Eu<sup>2+</sup> using reference materials (EuCl<inf>2</inf> and EuCl<inf>3</inf>) and XPS measurements. The Eu<sup>2+</sup>-activator ions occupied in the interstitial sites of the SiO<inf>2</inf> matrix were confirmed by FT-IR, XPS, and <sup>29</sup>Si MAS-NMR spectroscopy. Even though the void spaces formed structurally in both α-quartz and α-cristobalite can accommodate Eu<sup>2+</sup> ions (ionic radius = 1.25 Å at CN = 8), SiO<inf>2</inf>:Eu<sup>2+</sup> compound fired at 1300°C under a hydrogen atmosphere is destined to be deficient in O or Si atoms, indicating the formation of the wider void spaces in the SiO<inf>2</inf> crystal lattice. A sputtered depth profile of SiO<inf>2</inf>-related compounds obtained by time-of-flight secondary ion mass spectrometry (TOF-SIMS) corroborates the O-defective SiO<inf>2</inf> induced by hydrogen. In particular, the interatomic potentials, depending on the interstitial positions of Eu atoms in α-cristobalite and α-quartz, are calculated based on Lennard-Jones and coulomb potentials. For α-cristobalite, the minimum potential value is -51.47 eV and for α-quartz, the value is 221.8 eV, which reveals that the Eu<sup>2+</sup>-activator ions more preferably enter the interstitial sites of α-cristobalite than those of α-quartz. Thanks to the stable Eu<sup>2+</sup>-activator ions enclosed by Si-O linkages, the SiO<inf>2</inf>:Eu<inf>0.002</inf><sup>2+</sup> compound emits blue light and its PL emission intensity is about 24 times higher than that of the O-defective SiO<inf>2</inf> compound. This phosphor material could be a platform for modeling a new phosphor and for application in the solid-state lighting field.

Original languageEnglish (US)
Pages (from-to)74790-74801
Number of pages12
JournalRSC Advances
Volume5
Issue number91
DOIs
StatePublished - Aug 12 2015

ASJC Scopus subject areas

  • Chemical Engineering(all)
  • Chemistry(all)

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