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Temperaturas de transición de vidrio impar-par en el homólogo de vidrio iónico formador de redes

Ke Yang¹, Madhusudan Tyagi, Jeffrey S Moore

¹Beckman Institute for Advanced Science and Technology, ‡Department of Materials Science and Engineering, ∥Department of Chemistry, and #Department of Nuclear, Plasma, and Radiological Engineering, University of Illinois at Urbana-Champaign , Urbana, Illinois 61801, United States.

Journal of the American Chemical Society

|January 15, 2014

Resumen

Los vidrios iónicos exhiben efectos impares e impares inesperados en las temperaturas de transición de vidrio, vinculados a la simetría estructural y dinámica molecular. Este hallazgo desafía las suposiciones anteriores sobre materiales amorfos.

Área de la Ciencia:

Ciencia de los materiales Ciencia de los materiales.
Química del estado sólido.
La Química Física es la química física.

Sus antecedentes:

Los efectos impares están bien documentados en materiales cristalinos, que influyen en las propiedades físicas basadas en unidades estructurales.
Tales efectos generalmente no se anticipan en materiales amorfos moleculares, incluidos los vidrios iónicos.
La comprensión de las relaciones estructura-propiedades en sólidos amorfos es crucial para el diseño de nuevos materiales.

Objetivo del estudio:

Para investigar la ocurrencia de efectos pares y impares en vidrios iónicos formadores de redes.
Explorar los orígenes moleculares de las alteraciones de propiedades observadas en sólidos amorfos.
Para correlacionar la dinámica atómica y la simetría estructural con la temperatura de transición de vidrio.

Principales métodos:

Síntesis de vidrios iónicos formadores de redes utilizando cationes multivalentes de amonio y aniones citrato.
Medición de las temperaturas de transición de vidrio para los sólidos amorfos sintetizados.
Experimentos de dispersión de neutrones elásticos incoherentes para sondear la dinámica atómica del nanosegundo.

Principales resultados:

Se observó un efecto impar y par distinto en las temperaturas de transición de vidrio de los vasos iónicos, correlacionado con la longitud de la columna vertebral.
Los datos de dispersión de neutrones revelaron diferencias en la movilidad atómica que se alinean con las temperaturas de transición de vidrio alternadas observadas.
El estudio encontró una correlación entre la simetría estructural molecular y la movilidad atómica.

Conclusiones:

Los vidrios iónicos formadores de redes pueden exhibir efectos impares, contrariamente a las expectativas para los materiales amorfos.
La simetría estructural molecular es un factor clave que influye en la movilidad atómica y la temperatura de transición de vidrio en estos vidrios iónicos.
Los hallazgos proporcionan nuevos conocimientos sobre el comportamiento fundamental de los sólidos amorfos y la naturaleza de los efectos impares-pares.

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