Local structure of Yb 3+ ions and X-ray induced defect in Yb-doped silica glass

Local structure around Yb 3+ ions in Yb-P-doped silica glasses and its P concentration dependence were elucidated by EXAFS measurements. Yb-O coordination number was found to change from 4 → 8 → 6 → 7 ∼ 8 with increasing the atomic ratio P/Yb. This strange change can be corresponded to the local structure changes in the order of YbPO 4 -like, Yb(PO 3 ) 3 -like to YbP 5 O 14 -like local structures. This correspondence is supported by various optical measurements, such as the Rayleigh/Mie scattering, Raman scattering, absorption cross-section, CT transition, and X-ray induced defect formation, which were also found to depend on P/Yb. These results provide a guideline of the suitable P concentration in RE-P-doped silica glasses for various applications.

Section: Sample Preparationmentioning

confidence: 76%

Section: The Rayleigh/mie Scatteringmentioning

confidence: 94%

Section: The Rayleigh/mie Scatteringmentioning

confidence: 99%

“…P/Yb ratio dependence of the scattering loss at 1/λ 4 = 20. In the inset, data of a sample with Yb = 0.05 wt%, P = 0% 19) is also shown for comparison.…”

Section: Raman Scatteringmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

P concentration dependence of local structure around Yb³⁺ ions and optical properties in Yb–P-doped silica glasses

Okazaki

Sekiya

Saito

2019

²⁷Al MAS NMR, EXAFS and X-ray induced absorption studies in Al-doped and Yb–Al-doped silica glasses fabricated by MCVD

Okazaki¹,

Arakawa²,

Sekiya³

et al. 2020

27Al MAS NMR, EXAFS, and X-ray induced absorption measurements have been carried out in Al-doped silica (AS: 0.4 wt% ≤ Al ≤ 6.3 wt%) and Yb–Al-doped silica (YAS: 0.02 wt% ≤ Yb ≤ 0.8 wt%, Al = 0.4 wt%) glasses fabricated by MCVD. AS and YAS glasses are found to contain the normal 4-, 5-, and 6-fold coordinated Al sites (Al(4), Al(5), and Al(6)). Furthermore, AS and YAS glasses have significant Al(4) intensities of 27Al NMR spectra in the range of chemical shift value at ∼38 ppm and ∼92 ppm, respectively. In AS glasses, Al(6) is dominant in Al < 1.5 wt%, but Al(4) rapidly increases with increasing Al concentration and its relative proportion becomes larger than that of Al(6). This behavior is contrary to the results in melt-quenching glasses. The Rayleigh scattering increases with increasing Al in AS glasses, indicating an onset of subnanometer scale clustering of Al. The mechanism of a pair generation of Al-OHC and Al-E’ center in AS glasses is proposed to be bond breaking of unstable triclusters composed of Al(n), Si(4) and Al(4) connected by O(3) with strained bonds. In YAS glasses, Al(4) increases with increasing Yb3+ concentration from 0 to 0.02 wt%, but Al(4) is almost constant with further increasing Yb. Yb–O coordination number, deduced from EXAFS, is ∼7, and it is almost independent of Yb concentration. These results suggest that neutralization of Yb3+ can be done not only Al(4), but also Al(5) and Al(6). A pair generation of Al-OHC and Yb2+ is more likely generated than a pair generation of Al-OHC and Al-E’ center in YAS glasses. This is caused by the fact that Yb2+ and/or Al-OHC in YAS glasses have deeper trapping levels than Al-E’ and/or Al-OHC in AS glasses , which are confirmed by annealing measurements. A plausible precursors of Yb2+ and Al-OHC is a tricluster composed of Al(n), Si(4) and Yb(7) connected by O(3).

The difference in the coordination environment around Yb³⁺ ions between Yb–Al-doped and Yb–P-doped silica glasses

Okazaki

Sekiya

Saito

2020

To examine the difference in coordination environment around Yb3+ ions between Yb–Al-doped (YAS) and Yb–P-doped (YPS) silica glasses, Al/Yb dependence of the local structure around Yb3+ ions was investigated by EXAFS and optical measurements in YAS glasses and compared with the previous results of the P/Yb dependence in YPS glasses. It was found that Al3+ ions gradually coordinate to the Yb3+ ions with increasing Al/Yb from 0 to 20, and Yb–O coordination number changes from 4 to 8 in YAS, while in YPS glasses P5+ ions rapidly coordinate to the Yb3+ ions with increasing P/Yb. Contrary to the slow change of the coordination structure in YAS glass, the clustering of Yb3+ ions in YPS is immediately suppressed even if Al/Yb is ∼0.4. The reason must be that Yb3+ is easy to take local charge compensation in YAS glasses, just as charge neutralization of Al3+ ions in Al-doped silica glasses. The local structure model, where the mixed existence of O(3) an Al(n) contributes to charge compensation around Yb3+ ions in YAS glasses, was proposed.