Phase separation in alkali silicate glasses detected through inverse Laplace transform of Si nuclear magnetic resonance echo train decay
The ratio of silicon-29 nuclear magnetic resonance (NMR) coherence lifetimes for Q 4 and Q 3 sites under magic-angle spinning and a train of π pulses in a series of binary alkali silicate glasses is used to detect phase separation, even at small scales where the glass appears optically homogenous. T...
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| Published in | Journal of materials chemistry. C, Materials for optical and electronic devices Vol. 1; no. 42; pp. 15792 - 1585 |
|---|---|
| Main Authors | , , , , |
| Format | Journal Article |
| Language | English |
| Published |
03.11.2022
|
| Online Access | Get full text |
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| Summary: | The ratio of silicon-29 nuclear magnetic resonance (NMR) coherence lifetimes for Q
4
and Q
3
sites under magic-angle spinning and a train of π pulses in a series of binary alkali silicate glasses is used to detect phase separation, even at small scales where the glass appears optically homogenous. This approach exploits the dependence of echo train coherence lifetimes on the residual heteronuclear dipolar coupling between Si-29 and the NMR active nuclei of neighboring network modifier cations. The shifted-echo phase incremented echo train acquisition NMR method is used to eliminate modulation of the echo train amplitudes due to
J
couplings across Si-O-Si linkages. A 2D Fourier and inverse Laplace transform of this dataset provides a correlation of the isotropic
29
Si chemical shift to echo train coherence lifetimes, giving a sensitive probe of phase separation as well as chemical composition and local structure of the different phases. The
29
Si Q
4
:Q
3
mean coherence lifetime ratios are 28.8, 23.8, and 5.8 in the phase-separated glasses, 0.05Li
2
O·0.95SiO
2
, 0.1Li
2
O·0.9SiO
2
and 0.05Na
2
O·0.95SiO
2
, respectively, while the ratio is reduced to 2.1, 1.6, and 1.6 in glasses not exhibiting signs of phase separation, 0.05K
2
O·0.95SiO
2
, 0.05Cs
2
O·0.95SiO
2
and 0.10Cs
2
O·0.90SiO
2
, respectively. Phase separation inhibition, through addition of alumina, is also verified in 0.07Li
2
O·0.02Al
2
O
3
·0.91SiO
2
.
The ratio of Si-29 nuclear magnetic resonance coherence lifetimes for Q
4
and Q
3
sites under magic-angle spinning and a π-pulse train in silicate glasses can detect phase separation, even at small scales where the glass appears optically homogenous. |
|---|---|
| Bibliography: | https://doi.org/10.1039/d2tc03542a Electronic supplementary information (ESI) available: Background NMR theory of residual dipolar couplings, the best-fit parameters obtained from the least-squares analysis of the spectra in photographs of 5Na:95Si, 5Li:95Si, and 10Li:90Si glasses, X-ray diffraction data of the 5Li:95Si and 10Li:90Si glasses, and the parameters for the inverse Laplace transforms of the experimental datasets. See DOI Fig. 2 |
| ISSN: | 2050-7526 2050-7534 |
| DOI: | 10.1039/d2tc03542a |