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Structural Studies of Fluoroborate Laser Glasses by Solid State NMR and EPR Spectroscopies
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文摘
The structure of glasses in the systems (100 – x)B<sub>2sub>O<sub>3sub>–xPbF<sub>2sub> (x = 30, 40, and 50) and 50B<sub>2sub>O<sub>3sub>–(50 – x)PbO–xPbF<sub>2sub> (x = 5, 10, 15, 20, 25, 30, 35, 40, and 45) has been studied by solid state NMR and EPR spectroscopies. On the basis of <sup>11sup>B and <sup>19sup>F high resolution solid state NMR as well as on <sup>11sup>B/<sup>19sup>F double resonance results, we develop a quantitative structural description on the atomic scale. <sup>19sup>F NMR results indicate a systematic dependence of the fluoride speciation on PbF<sub>2sub> content: At low x-values, F<sup>–sup> ions are predominantly found on BO<sub>3/2sub>F<sup>–sup> units, whereas, at higher x-values, fluoride tends to be sequestrated into amorphous domains rich in PbF<sub>2sub>. In addition, both pulsed EPR studies of Yb<sup>3+sup> doped glasses and photophysical studies of Eu<sup>3+sup> doped samples indicate a mixed fluoride/borate coordination of the rare-earth ions and the absence of nanophase segregation effects.

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