Mechanics and electrical conductivity of dislocation-tuned ceramics
Mechanics and electrical conductivity of dislocation-tuned ceramics
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位错调谐陶瓷的力学和电导率
DOI：
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发表时间：
2021
期刊：
影响因子：
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通讯作者：
L. Porz
中科院分区：
文献类型：
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作者：
L. Porz
位错因其调节陶瓷一系列功能特性的潜力而受到越来越多的关注。作为一维线缺陷，它们通过弹性应变场以及具有补偿空间电荷的带电核心来影响其环境。这可能是点缺陷掺杂的一种竞争方法。它们的几何多功能性和局部影响同时允许新的设计尺寸并带来新的复杂性层次。位错还严重影响机械性能，这需要对其力学及其对每种功能性能的影响有相互关联的了解，从而使研究工作变得非常复杂。
特别是，位错影响功能特性（例如导电性和导热性）的详细机制以及相应的设计参数尚未得到充分探索。此外，需要开发将位错引入多晶样品的方法。最后，需要重新审视位错对陶瓷断裂韧性的作用。关于所有这三个问题的文献都很丰富。然而，它分散在数十年的时间和一系列不同的材料中，这阻碍了对需要解决的关键问题的概述和快速识别。
在这项工作中，通过首先提出陶瓷位错力学的简单观点来确定关键潜力。这导致了对室温塑性和断裂韧性的更长时间的讨论：位错在环境温度下在多种陶瓷中是可移动的。虽然这些单晶具有延展性，但它们各自的多晶却没有延展性，并且尽管具有延展性，但它们都表现出脆性。我们尝试对这种看似矛盾的机械行为进行连贯的解释，同时表明位错可以意外地显着提高陶瓷的断裂韧性。此外，在高温压缩测试中，位错结构被引入到多晶中。这使得多晶的高温变形性和位错结构设计合理化。最后，开发了一个概念框架来简化有关位错对电导率等功能特性影响的尖锐讨论。
在讨论的三个主题中，1) 室温塑性和断裂韧性，2) 高温塑性，3) 导电性，将尝试充分考虑机械复杂性。将得出更简单的观点，从而更容易、更准确地判断这三个领域中每个领域的潜力。
Dislocations are attracting increasing attention for their potential to tune a whole range of functional properties in ceramics. As one-dimensional line defects, they influence their environment by both their elastic strain field as well as their charged core with compensating space charge. This can be a competing approach to point defect doping. Their geometric versatility and localized impact simultaneously allow new design dimensions and pose new layers of complexity. Dislocations also severely impact mechanical properties, which demands an interrelated understanding of both their mechanics and their impact on each functional property, severely complicating research efforts.
In particular, the detailed mechanisms by which dislocations impact functional properties, such as electrical and thermal conductivity, and the respective design parameters are not fully explored. Furthermore, ways to introduce dislocations into polycrystalline samples need to be developed. And lastly, the role of dislocations on the fracture toughness of ceramics needs to be revisited. Literature on all of these three questions is abundantly available. However, it is scattered over decades and a range of different materials, which impedes overview and quick identification of critical questions to be addressed.
In this work, key potential is identified by first presenting a simple perspective on dislocation mechanics in ceramics. This leads to a longer discussion on room temperature plasticity and fracture toughness: Dislocations are mobile at ambient temperature in a broad range of ceramics. While these single crystals are ductile, their respective polycrystals not ductile and both behave brittle despite their ductility. A coherent explanation for this seemingly contradicting mechanical behavior is attempted while suggesting that dislocations can unexpectedly enhance the fracture toughness of ceramics substantially. Furthermore, dislocation structures are introduced into polycrystals in compression tests at elevated temperatures. This allows the rationalization of the high-temperature deformability and designing dislocation structures in polycrystals. Lastly, a conceptual framework is developed to simplify pointed discussions on the impact of dislocations on functional properties such as conductivity.
In each of the three topics discussed, 1) room temperature plasticity and fracture toughness, 2) high temperature plasticity, and 3) conductivity, attempts will be made to fully embrace the mechanistic complexity. Simpler perspectives will be derived allowing easier and more accurate judgement of the potential in each of the three fields.