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Resolución de las diferentes dinámicas de las subratillas de flúor en el conductor aniónico BaSnF(4) mediante el uso
Santanu Chaudhuri1, Francis Wang, Clare P Grey
1Department of Chemistry, State University of New York, Stony Brook, NY 11794-3400, USA.
Journal of the American Chemical Society
|September 26, 2002
Resumen
El conductor de iones fluoruro BaSnF(4) exhibe dos subtiendas de flúor distintas. Los iones fluoro móviles entre las capas Ba y Sn facilitan una conductividad 2D rápida, con una conductividad 3D más lenta que requiere saltos entre capas.
Área de la Ciencia:
- Química del estado sólido.
- Ciencia de los materiales ciencia de los materiales.
- Espectroscopia de resonancia magnética nuclear por resonancia magnética.
Sus antecedentes:
- BaSnF ((4) pertenece a la familia MSnF ((4), conocida por su conductividad aniónica relacionada con la fluorita.
- La comprensión de la movilidad iónica es crucial para el desarrollo de materiales conductores avanzados.
- Los conductores de iones de fluoruro son componentes clave en los dispositivos electroquímicos.
Objetivo del estudio:
- Para investigar la dinámica de los iones fluoruro en BaSnF ((4) utilizando técnicas avanzadas de RMN.
- Para dilucidar los mecanismos de conductividad iónica en este material en capas.
- Para correlacionar las características estructurales con la movilidad de iones y la conductividad observada.
Principales métodos:
- Espectroscopia de resonancia magnética nuclear (RMN) de estado sólido, específicamente 19F y 119Sn MAS RMN.
- Experimentos de temperatura variable para estudiar la dinámica iónica en un amplio rango de temperaturas (-150 a 250 °C).
- 19F-119Sn polarización cruzada (CP) e intercambio 2D experimentos de RMN para sondear entornos locales y el intercambio iónico.
Principales resultados:
- Se identificaron dos subrejas de flúor distintas: una subreja rígida en capas de Ba2+ y una subreja móvil entre capas de Ba/Sn.
- Movimiento de iones extremadamente rápido (tiempo de correlación < 3 x 10^-5 s a -100 °C) observado para la subrejilla móvil.
- Hay evidencia de un intercambio lento entre subrejas rígidas y móviles, y una congelación casi completa del movimiento por debajo de -150 °C.
Conclusiones:
- Los resultados respaldan un modelo de conductividad anisotrópica bidimensional rápida dentro de la subtela móvil de fluoruro.
- La conductividad tridimensional está limitada por procesos de salto mucho más lentos entre capas.
- La espectroscopia de RMN efectivamente distingue y cuantifica la movilidad iónica en estructuras de capas complejas como BaSnF.
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