Local and global dynamics of the viscous ion conductors 2Ca(NO3)2-3KNO3 and 2Ca(NO3)2-3RbNO3 probed by 87Rb nuclear magnetic resonance and shear rheology

Joachim Beerwerth; S. Peter Bierwirth; Jens Adam; Catalin Gainaru; Roland Böhmer

doi:10.1063/1.5093973

Local and global dynamics of the viscous ion conductors 2Ca(NO₃)₂-3KNO₃ and 2Ca(NO₃)₂-3RbNO₃ probed by ⁸⁷Rb nuclear magnetic resonance and shear rheology

Joachim Beerwerth, S. Peter Bierwirth, Jens Adam, Catalin Gainaru, Roland Böhmer

Research output: Contribution to journal › Article › peer-review

17 Scopus citations

Abstract

The microscopic and macroscopic dynamics of calcium alkali nitrate melts are studied in their supercooled regime by means of shear rheology and nuclear magnetic resonance (NMR). The structural relaxation is probed using shear rheology to access the viscoelastic flow as well as using physical aging experiments. By exploiting the strongly quadrupole-perturbed ⁸⁷Rb nucleus, the local dynamics is probed on the milliseconds to nanoseconds range using various NMR methods involving central-transition stimulated-echo techniques, line shape analyses, spin relaxations, and second-order dynamic shift effects. The time scales monitored via the local Rb probe are in harmony with the electrical conductivity relaxation times. The low-temperature NMR line shapes agree excellently with those predicted by the Czjzek model. The temperature dependent second-order dynamic frequency shift is described using the imaginary part of the spectral density. It is demonstrated how the latter quantity can be generalized to include effects of correlation time distributions.

Original language	English
Article number	194503
Journal	Journal of Chemical Physics
Volume	150
Issue number	19
DOIs	https://doi.org/10.1063/1.5093973
State	Published - May 21 2019
Externally published	Yes

Funding

Peter Lunkenheimer (Universität Augsburg) is cordially thanked for providing some of the nitrate glasses studied in the present work. Stimulating discussions with Burkhard Geil and Michael Storek are also acknowledged. Financial support was provided by the Deutsche Forschungsgemeinschaft under Grant Nos. BO1301/13-1, BO1301/14-1, and GA2680/1-1.

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Deutsche Forschungsgemeinschaft

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title = "Local and global dynamics of the viscous ion conductors 2Ca(NO3)2-3KNO3 and 2Ca(NO3)2-3RbNO3 probed by 87Rb nuclear magnetic resonance and shear rheology",

abstract = "The microscopic and macroscopic dynamics of calcium alkali nitrate melts are studied in their supercooled regime by means of shear rheology and nuclear magnetic resonance (NMR). The structural relaxation is probed using shear rheology to access the viscoelastic flow as well as using physical aging experiments. By exploiting the strongly quadrupole-perturbed 87Rb nucleus, the local dynamics is probed on the milliseconds to nanoseconds range using various NMR methods involving central-transition stimulated-echo techniques, line shape analyses, spin relaxations, and second-order dynamic shift effects. The time scales monitored via the local Rb probe are in harmony with the electrical conductivity relaxation times. The low-temperature NMR line shapes agree excellently with those predicted by the Czjzek model. The temperature dependent second-order dynamic frequency shift is described using the imaginary part of the spectral density. It is demonstrated how the latter quantity can be generalized to include effects of correlation time distributions.",

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AU - Beerwerth, Joachim

AU - Bierwirth, S. Peter

AU - Adam, Jens

AU - Gainaru, Catalin

AU - Böhmer, Roland

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Local and global dynamics of the viscous ion conductors 2Ca(NO₃)₂-3KNO₃ and 2Ca(NO₃)₂-3RbNO₃ probed by ⁸⁷Rb nuclear magnetic resonance and shear rheology

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