Symmetry Switching of Negative Thermal Expansion by Chemical Control

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• 作者：Mark S. Senn ; Claire A. Murray ; Xuan Luo ; Lihai Wang ; Fei-Ting Huang ; Sang-Wook Cheong ; Alessandro Bombardi ; Chris Ablitt ; Arash A. Mostofi ; Nicholas C. Bristowe
• 刊名：Journal of the American Chemical Society
• 出版年：2016
• 出版时间：May 4, 2016
• 年：2016
• 卷：138
• 期：17
• 页码：5479-5482
• 全文大小：335K
• 年卷期：0
• ISSN：1520-5126

文摘

The layered perovskite Ca_3–xSr_xMn₂O₇ is shown to exhibit a switching from a material exhibiting uniaxial negative to positive thermal expansion as a function of x. The switching is shown to be related to two closely competing phases with different symmetries. The negative thermal expansion (NTE) effect is maximized when the solid solution is tuned closest to this region of phase space but is switched off suddenly on passing though the transition. Our results show for the first time that, by understanding the symmetry of the competing phases alone, one may achieve unprecedented chemical control of this unusual property.