Stress-modulated optimization of polymorphic phase transition in Li-doped (K,Na)NbO3
Stress-modulated optimization of polymorphic phase transition in Li-doped (K,Na)NbO3
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DOI：
10.1063/5.0016072
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发表时间：
2020-07
影响因子：
4
通讯作者：
N. Khansur;Alexander Martin;K. Riess;H. Nishiyama;Keiichi Hatano;Ke Wang;Jingfeng Li;K. Kakimoto-K.-Kak
中科院分区：
文献类型：
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作者：
N. Khansur;Alexander Martin;K. Riess;H. Nishiyama;Keiichi Hatano;Ke Wang;Jingfeng Li;K. Kakimoto-K.-Kak
研究了单轴压应力对6摩尔分子晶体结构的影响。用同步辐射X射线衍射仪原位研究了掺Li%的(K，Na)NbO_3(LKNN6a)陶瓷，揭示了应力诱导的单斜相和四方相P4 mm相的相对变化。因此，LKNN6a的宏观力学行为除了晶格形变和磁畴转变外，还有应力诱导的相变。在恒定偏压下的介电常数测量表明，原位应力依赖的衍射数据也证明了一种机械调制多态相变温度(TPPT)到更高温度的方法。外加单轴压应力增加了低对称性单斜相的稳定性，使TPPT向高温移动60℃，最大单轴压应力为300 Mpa。重要的是，应力诱导的室温铁电相的稳定化有助于优化无铅KNN的相变区，并提高其温度稳定性。
The effect of uniaxial compressive stress on the crystal structure of a 6 mol. % Li-doped (K,Na)NbO3 (LKNN6a) ceramic was investigated using in situ synchrotron X-ray diffraction, revealing the stress-induced relative change in monoclinic Pm and tetragonal P4mm phases. As such, stress-induced phase transformations, in addition to the lattice deformation and domain switching, are the contributing factors for the observed macroscopic mechanical behavior of LKNN6a. The in situ stress-dependent diffraction data also demonstrates a method to mechanically modulate the polymorphic phase transition temperature (TPPT) to a higher temperature, as observed by the temperature-dependent permittivity measurements under a constant bias stress. The external uniaxial compressive stress increases the stability of the lower symmetry monoclinic phase, shifting TPPT to a higher temperature by 60 °C for the maximum uniaxial compressive stress of 300 MPa in the studied composition. Importantly, the stress-induced stabilization of the room-temperature ferroelectric phase can be useful to optimize the phase transition region, as well as increase the temperature stability of lead-free KNN.