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Measuring Magnetically-Tuned Ferroelectric Polarization in Liquid Crystals
Published on: August 15, 2018
Ferroelectricidad y fenómenos inducidos por la presión impulsados por la inestabilidad de valencia iónica neutra de
Reiji Kumai1, Sachio Horiuchi, Jun Fujioka
1Condensed Matter Research Center (CMRC) and Photon Factory, High Energy Accelerator Research Organization (KEK), Institute of Materials Structure Science, Tsukuba, 305-0801, Japan. reiji.kumai@kek.jp
Journal of the American Chemical Society
|December 7, 2011
Resumen
Los cocristales ferroeléctricos de fenazina con ácidos muestran cambios estructurales y transferencia de protones. La presión y la temperatura revelan diagramas de fase universales, impulsados por la inestabilidad de valencia y las interacciones de Coulomb.
Área de la Ciencia:
- Ciencia de los materiales Ciencia de los materiales.
- Química del estado sólido.
- La cristalografía es una técnica de cristalografía.
Sus antecedentes:
- Los cocristales ferroeléctricos supramoleculares ofrecen propiedades sintonizables a través de transformaciones estructurales.
- Comprender los mecanismos de transferencia de protones es clave para diseñar nuevos materiales electrónicos.
Objetivo del estudio:
- Investigar las transformaciones estructurales y las reacciones ácido-base en estado sólido en los cocristales de fenazina (Phz) con ácido cloránilico (H(2) ca), ácido brománilico (H(2) ba) y ácido fluoránilico (H(2) fa).
- Para aclarar el diagrama de fase presión-temperatura y los orígenes de la ferroelectricidad en estos sistemas.
Principales métodos:
- Mediciones de permisividad dieléctrica dependientes de la temperatura.
- Estudios de difracción de rayos X sincrotrón.
- Análisis de la transferencia de protones y las transiciones estructurales de fase.
Principales resultados:
- Los cocristales exhiben un desplazamiento incompleto de protones, formando estados semi-iónicos por debajo del punto de Curie.
- La ferroelectricidad en los cocristales Phz-H(2) fa es inducida por la presión hidrostática (~0,6 GPa).
- Las sucesivas transiciones de fase a fases moduladas incomensuradas y comensuradas ocurren a temperaturas más bajas.
- Se estableció un diagrama de fase de presión-temperatura universal, que revela estados básicos distintos a la presión ambiente.
Conclusiones:
- La interacción entre las transformaciones estructurales y la transferencia de protones dicta el comportamiento ferroeléctrico.
- La inestabilidad de valencia y las interacciones de Coulomb frustradas impulsan la desproporción de carga y el ordenamiento espacial único.
- Estos hallazgos proporcionan información sobre el diseño de materiales ferroeléctricos avanzados.
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