title: Sulfate Exchange of the Nitrate-Type Layered Hydroxide Nanosheets of Ln2(OH)5NO3·nH2O for Better Dispersed and Multi-color Luminescent Ln2O3 Nanophosphors (Ln = Y0.98RE0.02, RE = Pr, Sm, Eu, Tb, Dy, Ho, Er, and Tm).
abstract: Through restricting thickness growth by performing coprecipitation at the freezing temperature of ~4 °C, solid-solution nanosheets (up to 5-nm thick) of the Ln2(OH)5NO3·nH2O layered hydroxide (Ln = Y0.98RE0.02; RE = Pr, Sm, Eu, Tb, Dy, Ho, Er, and Tm, respectively) were directly synthesized without performing conventional exfoliation. In situ exchange of the interlayer NO3 (-) with SO4 (2-) produced a sulfate derivative [Ln2(OH)5(SO4)0.5·nH2O] of the same layered structure and two-dimensional crystallite morphology but substantially contracted d 002 basal spacing (from ~0.886 to 0.841 nm). The sulfate derivative was systematically compared against its nitrate parent in terms of crystal structure and phase/morphology evolution upon heating. It is shown that the interlayer SO4 (2-), owing to its bonding with the hydroxide main layer, significantly raises the decomposition temperature from ~600 to 1000 °C to yield remarkably better dispersed oxide nanopowders via a monoclinic Ln2O2SO4 intermediate. The resultant (Y0.98RE0.02)2O3 nanophosphors were studied for their photoluminescence to show that the emission color, depending on RE(3+), spans a wide range in the Commission Internationale de l'Eclairage (CIE) chromaticity diagram, from blue to deep red via green, yellow, orange, and orange red.
authors.affiliation: Key Laboratory for Anisotropy and Texture of Materials (Ministry of Education), School of Materials Science and Engineering, Northeastern University, Shenyang, Liaoning, 110819, China.|College of Material Science and Engineering, Guilin University of Technology, Guilin, Guangxi, 541004, China.
authors.forename: Xiaoli
authors.initials: X
authors.lastname: Wu
authors.affiliation: Key Laboratory for Anisotropy and Texture of Materials (Ministry of Education), School of Materials Science and Engineering, Northeastern University, Shenyang, Liaoning, 110819, China.
authors.forename: Weigang
authors.initials: W
authors.lastname: Liu
authors.affiliation: Key Laboratory for Anisotropy and Texture of Materials (Ministry of Education), School of Materials Science and Engineering, Northeastern University, Shenyang, Liaoning, 110819, China. LI.Jiguang@nims.go.jp.|Materials Processing Unit, National Institute for Materials Science, Tsukuba, Ibaraki, 305-0044, Japan. LI.Jiguang@nims.go.jp.
authors.forename: Ji-Guang
authors.initials: JG
authors.lastname: Li
authors.affiliation: Key Laboratory for Anisotropy and Texture of Materials (Ministry of Education), School of Materials Science and Engineering, Northeastern University, Shenyang, Liaoning, 110819, China.
authors.forename: Qi
authors.initials: Q
authors.lastname: Zhu
authors.affiliation: Key Laboratory for Anisotropy and Texture of Materials (Ministry of Education), School of Materials Science and Engineering, Northeastern University, Shenyang, Liaoning, 110819, China.
authors.forename: Xiaodong
authors.initials: X
authors.lastname: Li
authors.affiliation: Key Laboratory for Anisotropy and Texture of Materials (Ministry of Education), School of Materials Science and Engineering, Northeastern University, Shenyang, Liaoning, 110819, China.
authors.forename: Xudong
authors.initials: X
authors.lastname: Sun
keywords: Anion exchange; Luminescence; Nanosheets; Oxide phosphor; Phase evolution