Controlled synthesis of layered rare-earth hydroxide nanosheets leading to highly transparent (Y0.95Eu0.05)2O3 ceramics

Bin Lu, Ji Guang Li, Tohru S. Suzuki, Mehdi Estili, Weigang Liu, Xudong Sun, Yoshio Sakka

Research output: Contribution to journalArticlepeer-review

27 Citations (Scopus)

Abstract

Chemical precipitation at the freezing temperature of ∼4°C has directly yielded layered rare-earth hydroxide [LRH, Ln2(OH)5NO3·nH2O, Ln = Y0.95Eu0.05] nanosheets (up to 7 nm thick) for the Y/Eu binary system, with the interlayer NO3- exchangeable with SO42-. Calcining the sulfate derivative at 1100°C for 4 h produces well-dispersed and readily sinterable Ln2O3 red phosphor powders (∼14.8 m2/g) that can be densified into highly transparent ceramics via optimized vacuum sintering at the relatively low temperature of 1700°C for 4 h (average grain size ∼14 μm; in-line transmittance ∼80% at the 613 nm Eu3+ emission or ∼99% of the theoretical transmittance of Y2O3 single crystal). Our systematic studies also found that (1) the extent of SO42- exchange and the interlayer distance of LRH are both affected by the SO42-/Ln3+ molar ratio (R), and an almost complete exchange is achievable at R = 0.25 as expected from the chemical formula (one SO42- replaces two NO3- for charge balance). The optimal R value for sintering, however, was found to be 0.03; (2) The Ln3+ concentration for LRH synthesis substantially affects properties of the resultant oxides, and hard agglomeration has been significantly reduced at the optimized Ln3+ concentration of 0.05-0.075 mol/L; (3) Sulfate exchange significantly alters the thermal decomposition pathway of LRH, and was found essential to produce well-dispersed and highly sinterable oxide powders; (4) Both the oxide powders and transparent ceramics exhibit the typical red emission of Eu3+ at ∼613 nm (the 5D07F2 transition) under charge-transfer (CT) excitation. Red-shifted CT band center, stronger excitation/emission, and shorter fluorescence lifetime were, however, observed for the transparent ceramics.

Original languageEnglish
Pages (from-to)1413-1422
Number of pages10
JournalJournal of the American Ceramic Society
Volume98
Issue number5
DOIs
Publication statusPublished - 2015 May 1

ASJC Scopus subject areas

  • Ceramics and Composites
  • Materials Chemistry

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