Phase Stability in Nanocrystals: A Predictive Diagram for Yttria-Zirconia
Phase Stability in Nanocrystals: A Predictive Diagram for Yttria-Zirconia
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DOI：
10.1111/jace.13504
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发表时间：
2015-04-01
影响因子：
3.9
通讯作者：
Castro, Ricardo H. R.
中科院分区：
文献类型：
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作者：
Drazin, John W.;Castro, Ricardo H. R.
预测纳米晶体的晶型稳定性需要考虑来自固-气界面的热力学效应。随着微量热学的最新进展，最终有可能获得可靠的表面能数据，从而可以建立预测图，如通常的块状晶体相图，纳米晶体的相图。氧化钇掺杂氧化锆(YZ)目前被广泛应用，使其成为迄今为止研究最多的氧化物系统之一。然而，与块体YZ相比，纳米晶YZ(NYZ)的多晶性知之甚少，立方晶型、四方型、单斜晶型和非晶型在纳米尺度上的稳定性条件到目前为止还只是经验上的定义。在这项工作中，我们提出了一个新的预测纳米尺度的NYZ相图使用前所未有的数据表面能和体热测量获得的微量热。相图显示了稳定的氧化锆晶型与成分和尺寸的函数关系。这是一个有用的工具，也是对相对未接触的体相图的重要和新颖的改进，它掌握着可靠材料设计的关键。
Predicting the polymorphic stability of nanocrystals entails taking into account the thermodynamic effects from solid-vapor interfaces. With recent advances in microcalorimetry, it is finally possible to obtain reliable surface energy data which allow building of predictive diagrams, such as the usual phase diagrams for bulk crystals, for nanocrystals. Yttria doped zirconia (YZ) is currently utilized in a variety of applications; making it one of the most studied oxide systems to date. However, the polymorphism of nanocrystalline YZ (nYZ) is much less understood as compared to its bulk counterpart, and the stability conditions of cubic, tetragonal, monoclinic, and amorphous polymorphs at the nanoscale is so far only empirically defined. In this work, we present a new predictive nanoscale phase diagram for nYZ using unprecedented data on surface energies and bulk enthalpies acquired by microcalorimetry. The phase diagram shows the stable zirconia polymorph as a function of the composition and size. This is a useful tool and an important and novel advancement to relatively untouched bulk phase diagrams, which holds the key for reliable materials' design.