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Methods of Ex Situ and In Situ Investigations of Structural Transformations: The Case of Crystallization of Metallic Glasses
Published on: June 7, 2018
Cation size effects in mixed-ion metaphosphate glasses: structural characterization by multinuclear solid state NMR
J Schneider1, J Tsuchida, H Eckert
1Instituto de Física de São Carlos, Universidade de São Paulo, Av. Trabalhador Saocarlense 400, CEP 13566-590, São Carlos, SP, Brasil. schnei@ifsc.usp.br
Physical Chemistry Chemical Physics : PCCP
|July 24, 2013
Summary
Mixed-ion effects in metaphosphate glasses depend on cation size mismatch. NMR studies reveal that while cation size influences local environments, it doesn't solely determine ion mixing, suggesting complex mechanisms behind these effects.
Area of Science:
- Materials Science
- Solid-State Chemistry
- Glasses and Ceramics
Background:
- Metaphosphate glasses with two monovalent ions exhibit mixed-ion effects (MIE) in conductivity and glass transition temperature.
- These MIE are strongly influenced by the size difference between the mobile cations.
- Understanding the relationship between cation size mismatch and structural properties is crucial for MIE development.
Purpose of the Study:
- To investigate the correlation between cation size mismatch and structural properties in mixed-ion metaphosphate glasses.
- To analyze the local environments and spatial distribution of mobile ions using NMR spectroscopy.
- To compare MIE in systems with large cation size mismatches (Cs-Li, Rb-Li, Cs-Ag) with a reference system (Na-Ag).
Main Methods:
- Nuclear Magnetic Resonance (NMR) spectroscopy: (31)P, (87)Rb, (109)Ag, and (133)Cs NMR.
- Spin-Echo (SE) NMR for diffusion dynamics.
- Stimulated Echo Delayed Double Resonance (SEDOR) experiments for spatial distribution analysis.
Main Results:
- Local coordination environments of Ag(+), Rb(+), and Cs(+) ions show compositional trends related to ionic radius.
- Cs-Li metaphosphate glasses exhibit a random mixture of cations, contradicting segregation observed in Na-based glasses.
- Ag(+) mobility decreases significantly with Cs(+) substitution, indicating separate diffusion pathways, while Na(+) substitution shows cooperative hopping.
Conclusions:
- Cation size mismatch is not the sole determinant of cation segregation or non-statistical mixing in glasses.
- Compositional differentiation of structural sites contributes to MIE.
- The findings provide insights into the complex interplay of structure and dynamics governing mixed-ion effects in glasses.
