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Disorder in Mn+1AXn phases at the atomic scale.

  • Author(s): Wang, Chenxu
  • Yang, Tengfei
  • Tracy, Cameron L
  • Lu, Chenyang
  • Zhang, Hui
  • Hu, Yong-Jie
  • Wang, Lumin
  • Qi, Liang
  • Gu, Lin
  • Huang, Qing
  • Zhang, Jie
  • Wang, Jingyang
  • Xue, Jianming
  • Ewing, Rodney C
  • Wang, Yugang
  • et al.
Abstract

Atomic disordering in materials alters their physical and chemical properties and can subsequently affect their performance. In complex ceramic materials, it is a challenge to understand the nature of structural disordering, due to the difficulty of direct, atomic-scale experimental observations. Here we report the direct imaging of ion irradiation-induced antisite defects in Mn+1AXn phases using double CS-corrected scanning transmission electron microscopy and provide compelling evidence of order-to-disorder phase transformations, overturning the conventional view that irradiation causes phase decomposition to binary fcc-structured Mn+1Xn. With the formation of uniformly distributed cation antisite defects and the rearrangement of X anions, disordered solid solution γ-(Mn+1A)Xn phases are formed at low ion fluences, followed by gradual transitions to solid solution fcc-structured (Mn+1A)Xn phases. This study provides a comprehensive understanding of the order-to-disorder transformations in Mn+1AXn phases and proposes a method for the synthesis of new solid solution (Mn+1A)Xn phases by tailoring the disorder.

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