Network Structure and Rare-Earth Ion Local Environments in Fluoride Phosphate Photonic Glasses Studied by Solid-State NMR and Electron Paramagnetic Resonance Spectroscopies

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• 作者：Marcos de Oliveira Jr. ; Tobias Uesbeck ; T谩ssia S. Gon莽alves ; Claudio Jos茅 Magon ; Paulo S. Pizani ; Andrea S. S. de Camargo ; Hellmut Eckert
• 刊名：Journal of Physical Chemistry C
• 出版年：2015
• 出版时间：October 29, 2015
• 年：2015
• 卷：119
• 期：43
• 页码：24574-24587
• 全文大小：799K
• ISSN：1932-7455

文摘

A detailed structural investigation of a series of fluoride phosphate laser glasses with nominal composition 25BaF₂鈥?5SrF₂鈥?30 鈥?x)Al(PO₃)₃鈥?i>xAlF₃鈥?20 鈥?z)YF₃:zREF₃ with x = 25, 20, 15 and 10, RE = Yb and Eu, and 0 鈮?z 鈮?1.0 has been conducted using Raman, solid-state nuclear magnetic resonance (NMR), and electron paramagnetic resonance (EPR) spectroscopies. The network structure is dominated by the preferred formation of aluminum-to-phosphorus linkages, which have been quantified by means of ²⁷Al/³¹P NMR double-resonance techniques. The fluoride ions are found in mixed Al/Y/Ba/Sr environments accommodating the luminescent dopant species as well. The local environments of the rare-earth species have been studied by pulsed EPR spectroscopy of the Yb³⁺ spin probe (S = ¹/₂), revealing composition-dependent echo-detected lineshapes and strong hyperfine coupling with ¹⁹F nuclei in hyperfine sublevel correlation (HYSCORE) spectra consistent with the formation of Yb³⁺鈥揊 bonds. In addition, photoluminescence spectra of Eu³⁺-doped samples reveal that the ⁵D₀ 鈫?⁷F₂/⁵D₀ 鈫?⁷F₁ transitions intensity ratio, the normalized phonon sideband intensities in the excitation spectra, and excited state ⁵D₀ lifetime values are systematically dependent on fluoride content. Altogether, these results indicate that the rare-earth ions are found in a mixed fluoride/phosphate environment, to which the fluoride ions make the dominant contribution. Nevertheless, even at the highest fluoride levels (x = 25), the data suggest residual rare-earth鈥損hosphate coordination.