Effect of devitrification on ion motion in lithium-disilicate glass

Küchler, R.; Kanert, O.; Vereget, T.; Jain, Himanshu

doi:10.1016/j.jnoncrysol.2007.04.036

Cited by 12 publications

(6 citation statements)

References 29 publications

(41 reference statements)

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“…Nonexponential relaxation has been reported in glass-ceramics, where the different relaxing components are attributed to the nuclei in crystalline and amorphous regions. 14,34,36 The temperature dependence of short T 1 in Figure 3 is similar to that exhibited by the glass (Figure 2). In contrast, for long T 1 , the temperature dependence is different.…”

Section: Resultssupporting

confidence: 65%

“…For these glass-ceramic samples, the magnetization recovery to the equilibrium value was found to be nonexponential (Figure S4, Supporting Information) and the NMR data could be adequately fitted by the sum of two exponential functions with two different characteristic times, denoted “short T 1 ” (solid symbols in Figure ) and “long T 1 ” (open symbols in Figure ). Nonexponential relaxation has been reported in glass-ceramics, where the different relaxing components are attributed to the nuclei in crystalline and amorphous regions. ,, The temperature dependence of short T 1 in Figure is similar to that exhibited by the glass (Figure ). In contrast, for long T 1 , the temperature dependence is different.…”

Section: Resultssupporting

confidence: 59%

“…However, deviations from the BPP model are frequently encountered in disordered systems, where asymmetric relaxation curves and the T 1 –1 dependence on frequency less than ω o 2 have been observed. Nuclear relaxation studies on glasses have been interpreted in the framework of the coupling model theory, which assumes a stretched exponential (KWW) correlation resulting a spectral density function where n s is related to the stretched exponential parameter and is a measure of the asymmetry of the relaxation curve. ,,, To describe the main features of the 19 F relaxation curve in Figure , it is important to note that there is no homogeneous glassy phase throughout the NMR temperature range (300–637 K) because of the glass transition at 578 K. The 19 F relaxation rate maximum is observed below T g because of the low NMR frequency used in the experiments (36 MHz) . At the onset of crystallization, there is an apparent discontinuity in the relaxation time, suggesting that other types of relaxation mechanisms contribute to the 19 F relaxation.…”

Section: Resultsmentioning

confidence: 99%

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Magnetic Resonance and Conductivity Study of Lead–Cadmium Fluorosilicate Glasses and Glass-Ceramics

et al. 2018

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The fluorine motional dynamics in fluorosilicate glasses and glass-ceramics of the SiO2–PbF2–CdF2 system was investigated by complex impedance spectroscopy and 19F nuclear magnetic resonance (NMR) spectroscopy, and the coordination environment of a Cu2+ paramagnetic probe was examined by electron paramagnetic resonance (EPR) spectroscopy. Glass-ceramics were obtained by heat treatment of glass at a temperature between the glass-transition (T g) and the onset of crystallization (T x). Ionic conductivity of about 1.6 × 10–4 S/cm was obtained at 500 K for glass. The conductivity of the glass-ceramics was found to be lower than that obtained for the glass. The temperature dependence of the 19F NMR spin–lattice relaxation times was investigated between 300 and 770 K. The 19F NMR results of glass exhibit the qualitative features associated with fluorine mobility, namely, the presence of a relaxation rate maximum below T g. The NMR relaxation data of the glass-ceramics were analyzed assuming two fluorine dynamics. Continuous-wave EPR spectroscopy, using a Cu2+ ion as a probe, was employed to determine the local symmetry of the ion environment and the nature of relevant spin interactions. The hyperfine coupling of Cu2+ with the 19F, 113Cd, and 207Pb nuclei in the glass and the glass-ceramic was investigated by electron spin echo envelope modulation and hyperfine sublevel correlation spectroscopy.

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Section: Resultssupporting

confidence: 65%

Section: Resultssupporting

confidence: 59%

Section: Resultsmentioning

confidence: 99%

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Magnetic Resonance and Conductivity Study of Lead–Cadmium Fluorosilicate Glasses and Glass-Ceramics

et al. 2018

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“…In the present study (Fuss et al 2006;Kuchler et al 2007;Zheng et al 2007Zheng et al , 2008, XRD results revealed that lithium metasilicate represented the main crystalline phase after the first crystallization temperature. After further holding at the second crystallization temperature, metastable crystals gave way to lithium disilicate crystals which represented the main crystalline phase of four glass-ceramics after the second crystallization step.…”

Section: Thermal and Structural Analysissupporting

confidence: 53%

Effects of MO (M = Mg, Ca, Ba) on crystallization and flexural strength of semi-transparent lithium disilicate glass-ceramics

Luo

Zhou

et al. 2011

Bull Mater Sci

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In this study, semitransparent lithium disilicate glass-ceramics in the Li 2 O-K 2 O-Al 2 O 3-Y 2 O 3-La 2 O 3-SiO 2 system was investigated by incorporation of P 2 O 5 as nucleation agent and alkaline earth oxides as additive. The influence of alkaline earth oxides on the structure of glasses network, crystalline phases, microstructure and mechanical properties were investigated by means of Raman spectra, differential scanning calorimetry (DSC), X-ray diffractometry (XRD) and scanning electron microscopy (SEM). The mechanical strength was measured corresponding to norm ISO 6872. The Raman spectra predominantly showed that small additions of alkaline earth oxides not only form asymmetrical vibrations of the M-Si-O bonds, but also enhance the intensities of symmetrical vibrations of the P-O bonds, making the glass network more stable. And the small additions of CaO or BaO has more influence on the crystallization behaviour, crystalline phase, microstructure and mechanical properties of the glass-ceramics than the addition of MgO. The additions of alkaline earth oxides enhanced the first exothermic peak temperature but decreased the flexural strength of lithium disilicate glass-ceramics.

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“…In the present work, the system in the glassy state is used as the starting materials before introducing pores. A comparison of crystalline and glassy lithium disilicates reveals that the latter has a diffusion coefficient (and hence conductivity) of several orders larger than the former as shown by both experiment 25 and simulations. 22 Similar trends are also known for other systems, 26,27 for which both the crystalline and glassy states were examined.…”

Section: Introductionmentioning

confidence: 78%

Molecular dynamics study of nano-porous materials—Enhancement of mobility of Li ions in lithium disilicate

Habasaki

2016

The Journal of Chemical Physics

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In several nano-porous materials and their composites, enhancement of ionic conductivity has been reported and several mechanisms having different origins have been proposed so far. In the present work, ionic motion of Li ions in porous lithium disilicates is examined by molecular dynamics simulation in the constant volume conditions and the enhancement of the dynamics is predicted. Structures and dynamics of ions in a nano-porous system were characterized and visualized to clarify the mechanism of the enhancement. The diffusion coefficient of Li ions has shown the maximum in the medium density (and porosity) region, and near the maximum, shortening of the nearly constant loss region in the mean squared displacement of ions as well as changes of the structures of the coordination polyhedra, LiO is found. It suggests that the loosening of the cage, which increases the jump rate of ions, is an origin of the enhancement. When larger (but still in a nano-scale) voids are formed with a further decrease of density, more tight cages are reconstructed and the diffusion coefficient decreases again. These behaviors are closely related to the residual stress in the system. It is noteworthy that the explanation is not based on the percolation of the path only or formation of boundaries, although the former also affects the dynamics.

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Effect of devitrification on ion motion in lithium-disilicate glass

Cited by 12 publications

References 29 publications

Magnetic Resonance and Conductivity Study of Lead–Cadmium Fluorosilicate Glasses and Glass-Ceramics

Magnetic Resonance and Conductivity Study of Lead–Cadmium Fluorosilicate Glasses and Glass-Ceramics

Effects of MO (M = Mg, Ca, Ba) on crystallization and flexural strength of semi-transparent lithium disilicate glass-ceramics

Molecular dynamics study of nano-porous materials—Enhancement of mobility of Li ions in lithium disilicate

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