Europium valence control in the hydrothermal synthesis of apatites and borosilicates

JOURNAL OF ALLOYS AND COMPOUNDS

卷:656

Article

Kolis, Joseph W.¹ 

[1] Clemson Univ, Dept Chem, Clemson, SC 29634 USA

关键词: Crystal growth;    Rare earth compounds;    Luminescence;    X-ray diffraction;   

DOI  :  10.1016/j.jallcom.2015.08.279

来源: Elsevier

【 摘 要 】

The solid-state chemistry of novel metal silicate and borosilicate crystals containing Eu2+ and Eu3+ in high temperature hydrothermal fluids was investigated. It was found that europium ions could be readily incorporated into a number of crystals using a variety of simple glass-based feedstocks. The hydrothermal growth reactions were performed at nearly 600 degrees C in 1-5 M NaOH mineralizer fluids, and this was found to be a versatile route to both europium ion oxidation states with Eu acting as either a fundamental structural building block or a dopant ion. Several new single crystals were identified including two new apatites as well as a new europium borosilicate. The apatites crystallize in space group P6(3)/m with a = 9.4619(13) angstrom and c = 7.0054(14) angstrom for Eu-10(SiO4)(6)O-2, and a = 9.4413(13) A and c = 6.9087(14) angstrom for NaEu9(SiO4)(6)O-2. The new borosilicate, Eu2SiB2O8, crystallizes in space group Pbcn with a = 13.310(3) angstrom, b = 4.4247(9) angstrom and c = 9.2394(18) angstrom. The investigation of Eu-doped borosilicates demonstrated the strong blue emission generated from 370 nm excitation that was expected for the Eu2+ doped materials, as well as the less intense orange-red emission expected for the Eu3+ dopants. The hydrothermal reactions naturally facilitated a degree of europium reduction in Eu:Ba3Si2B6O16. It was found that the oxidation states of europium in the final product could be further controlled by using hydrazine as a reducing reagent. (C) 2015 Published by Elsevier B.V.

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