Chemical and dynamical speciation of mobile ions in the glassy fast ionic conductor Ag2S+B2S3+SiS2: A 109Ag nuclear magnetic resonance study

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2000-12-18
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Akai, Tomoko
Borsa, Ferdinando
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Martin, Steve
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Materials Science and Engineering

The Department of Materials Science and Engineering teaches the composition, microstructure, and processing of materials as well as their properties, uses, and performance. These fields of research utilize technologies in metals, ceramics, polymers, composites, and electronic materials.

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The Department of Materials Science and Engineering was formed in 1975 from the merger of the Department of Ceramics Engineering and the Department of Metallurgical Engineering.

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1975-present

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Abstract

109Ag NMR in the highly conductive glass 0.525Ag2S+0.475(0.5B2S3+0.5SiS2) was investigated from 230 to 433 K. The 109Ag NMR spectra reveal for the first time three well resolved lines corresponding to three kinds of chemically speciated Ag ions in sites with different chemical shifts in a macroscopically homogeneous glass. This chemical speciation of Ag ions is discussed in relation to the microstructure of the glass. As the temperature is increased, the three lines that originate from three different species of ions are narrowed, but these lines exist independently up to 433 K, the highest temperature measured. Nuclear spin-lattice relaxation rates (NSLR’s), 1/T1, were also measured. Two relaxation processes were found; one is associated with two of the chemically speciated Ag ions and the other is associated with the other Ag ions. The two different NSLR’s gradually approach a common value as the temperature is increased, and finally exhibit a common relaxation rate at and above 373 K. From the results of the NMR spectra and of the NSLR’s, which observe the ion dynamics on different time scales, it is concluded that the silver ions move fast within separate clusters of similar chemical environments (≫kHz), but exchange among the three different clusters at relatively slow rates (⩽100 Hz) above 373 K. From the time the ions reside at any one site, the mean free path of the ions is estimated.

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This article is from Physical Review B 63 (2000): 024303, doi:10.1103/PhysRevB.63.024303.

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Sat Jan 01 00:00:00 UTC 2000
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