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Issue 39, 2012
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Structure and luminescence behaviour of as-synthesized, calcined, and restored MgAlEu-LDH with high crystallinity

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Abstract

Highly crystalline Eu3+-incorporated MgAl layered double hydroxides (LDHs) were synthesized by the homogeneous precipitation method. For the crystals as-prepared, after their calcination from 200–1000 °C, and, further, after restoration in a Na2CO3 solution, the structural and luminescent changes were investigated for the first time. Eu3+ ions with a coordination number of, probably, 8, were incorporated into the hydrotalcite layer, which led to a basal spacing (dbasal) increase, microstrain formation, and crystalline morphology imperfections, while retaining the original lattice symmetry, R[3 with combining macron]m. In the deconstruction process due to calcination, the Eu3+ ions restrained the formation of the spinel phase from the layered double oxide (LDO), but did not significantly change the memory effect, by which LDOs can convert to LDHs during the hydration process. For the reversible phase transformation between LDH and LDO, the morphology observation revealed that, in addition to the formation of pores on the surface, nano-slabs were formed, especially for the restored crystals. A layered phase with a dbasal of 5.8 Å, due to bridging bidentate carbonates with the hydrotalcite layer, was formed in the calcination process at low temperature (300 °C) before the formation of LDO, but could not be restored to a large spacing. Typical 5D07FJ (J = 0–4) transitions of Eu3+ at 579, 593, 615, 653, and 698 nm were observed in the photoluminescence spectra and the intensity of the dominating 615 nm band decreased with the LDH deconstruction and the formation of free water, and then increased with the formation of LDOs in the calcination process, and vice versa in the reconstruction process. The Eu3+ ions had a probable 9- or 10-coordination mode in addition to the probable 8-coordination mode as the spinel phase appeared.

Graphical abstract: Structure and luminescence behaviour of as-synthesized, calcined, and restored MgAlEu-LDH with high crystallinity

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Publication details

The article was received on 10 Jun 2012, accepted on 10 Aug 2012 and first published on 13 Aug 2012


Article type: Paper
DOI: 10.1039/C2DT31249B
Citation: Dalton Trans., 2012,41, 12175-12184
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    Structure and luminescence behaviour of as-synthesized, calcined, and restored MgAlEu-LDH with high crystallinity

    Y. Zhao, J. Li, F. Fang, N. Chu, H. Ma and X. Yang, Dalton Trans., 2012, 41, 12175
    DOI: 10.1039/C2DT31249B

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