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Una transición aislante de metal en R2O2Bi con una inusual red cuadrada de Bi2 (R = tierras raras o Y)
Hiroshi Mizoguchi1, Hideo Hosono
1Frontier Research Center, Tokyo Institute of Technology, Midori-ku, Yokohama, Japan.
Journal of the American Chemical Society
|February 10, 2011
Resumen
Los investigadores sintetizaron nuevos compuestos R(2) O(2) Bi con una capa de aniones Bi(2-) única. La reducción del tamaño de los iones de tierras raras mejora la conductividad eléctrica, induciendo una transición metal-aislador debido a un agujero positivo en la capa de bismuto.
Área de la Ciencia:
- Química del estado sólido.
- Ciencia de los materiales ciencia de los materiales.
- Física de la materia condensada Física de la materia condensada Física de la materia condensada Física de la materia condensada Física de la materia condensada
Sus antecedentes:
- Los compuestos tetragonales de tipo ThCr(2)Si(2) ofrecen una plataforma para explorar nuevas propiedades electrónicas.
- La serie R(2)O(2)Bi introduce un inusual anión Bi(2-) que forma una red cuadrada 2D.
- Esta estructura está intercalada entre capas de fluorita cargadas positivamente, R(2) O(2) 2+).
Objetivo del estudio:
- Para sintetizar y caracterizar una serie de compuestos R(2) O(2) Bi.
- Para investigar la estructura de la banda electrónica y la conductividad de estos materiales.
- Comprender la relación entre los cambios estructurales y las propiedades electrónicas.
Principales métodos:
- Síntesis en estado sólido de compuestos R(2) O(2) Bi.
- Difracción de rayos X para la determinación estructural.
- Mediciones de conductividad eléctrica.
- Cálculos electrónicos de la estructura de la banda (implicado por la discusión de las bandas).
Principales resultados:
- Síntesis exitosa de los compuestos tetragonales R(2) O(2) Bi.
- Identificación de una red cuadrada 2D Bi(2-) con un agujero positivo por ión Bi(2-).
- Observación de una mayor conductividad eléctrica con la disminución del tamaño de los iones R.
- Demostración de una transición metal-insulador inducida por "presión química".
Conclusiones:
- La red cuadrada Bi(2-) en los compuestos R(2)O(2)Bi alberga bandas electrónicas 2D derivadas de las órbitas Bi 6p.
- La presencia de un agujero positivo en la capa Bi(2-) es crucial para la conductividad eléctrica.
- Las modificaciones estructurales, específicamente la reducción en el tamaño de la red cuadrada Bi(2-) a través de la presión química, influyen directamente y mejoran la conductividad, lo que lleva a una transición metal-aislador.
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