Microstructural phase coexistence kinetics near the polymorphic phase boundary
Microstructural phase coexistence kinetics near the polymorphic phase boundary
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DOI：
10.1016/j.actamat.2020.116579
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发表时间：
2021-03
期刊：
影响因子：
9.4
通讯作者：
O. A. Torres-Matheus;R. Edwin García;Catherine M. Bishop
中科院分区：
文献类型：
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作者：
O. A. Torres-Matheus;R. Edwin García;Catherine M. Bishop
通过建立一种新的铁电系统多相场模型，分析了无铅BZT-40 BCT中四方（T）相和菱方（R）相的共存。T和R相的亚稳共存之间的热力学上限T C，R= 49.90 ℃和动力学下限由时间-温度-转变行为确定的预测。预测的域微观结构表现出多面域壁和弯曲的TR相界面，这与最近的TEM研究在附近的多晶相边界（PPB）是一致的。此外，在PPB附近的域结构的小型化是相对低的界面能和由大的亚稳相分数引起的钉扎效应的结果，所述亚稳相分数源于相变的宏观驱动力的消失。特别地，当T→ TC，R时菱面体畴壁能量的消失使得相变诱导的极化旋转机制成为可能，并预测了R相的分级畴形态。这些结果与报告的R+ T共存的最高温度附近的更高的压电响应以及BZT-x BCT系统的R相中的微米尺寸的楔形域内的小型化纳米域结构的观察结果一致。
By implementing a novel multiphase field model for ferroelectric systems, the phase coexistence of the tetragonal (T) and rhombohedral (R) phases in Pb-free BZT-40BCT was analyzed. Metastable coexistence of the T and R phases is predicted between a thermodynamic upper limit at T C, R= 49.90∘ C and a kinetic lower limit determined by the time-temperature-transformation behaviour. Predicted domain microstructures exhibit faceted domain walls and curved TR phase interfaces that are consistent with recent TEM studies in the vicinity of the polymorphic phase boundary (PPB). Further, miniaturization of the domain structure near the PPB is a result of the relatively low interfacial energies and a pinning effect caused by the large metastable phase fraction that originates from the vanishing macroscopic driving force for phase transformation. Particularly, the vanishing of rhombohedral domain wall energies as T→ T C, R enables a phase transformation-induced polarization rotation mechanism and predicts a hierarchical domain morphology for the R phase. These results are in agreement with the higher piezoelectric response reported near the maximum temperature for R+ T coexistence and the observations of a miniaturized nanodomains structure within micron-sized, wedge-shaped domains in the R phase for the BZT-x BCT system.