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Controlled Synthesis of Layered Rare-Earth Hydroxide Nanosheets Leading to Highly Transparent (Y0.95Eu0.05)2O3 Ceramics.
- Source :
-
Journal of the American Ceramic Society . May2015, Vol. 98 Issue 5, p1413-1422. 10p. 2 Color Photographs, 2 Black and White Photographs, 6 Graphs. - Publication Year :
- 2015
-
Abstract
- Chemical precipitation at the freezing temperature of ~4°C has directly yielded layered rare-earth hydroxide [ LRH, Ln2( OH)5 NO3· 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 5D0→7F2 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. [ABSTRACT FROM AUTHOR]
Details
- Language :
- English
- ISSN :
- 00027820
- Volume :
- 98
- Issue :
- 5
- Database :
- Academic Search Index
- Journal :
- Journal of the American Ceramic Society
- Publication Type :
- Academic Journal
- Accession number :
- 102166759
- Full Text :
- https://doi.org/10.1111/jace.13488