Piezoelectricity in nominally centrosymmetric phases
Piezoelectricity in nominally centrosymmetric phases
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DOI：
10.1103/physrevresearch.3.043221
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发表时间：
2021-12-27
影响因子：
4.2
通讯作者：
Salje, Ekhard K. H.
中科院分区：
文献类型：
--
作者：
Aktas, Oktay;Kangama, Moussa;Salje, Ekhard K. H.
化合物相通常显示出相对于其标称平均晶体对称性的对称性被禁止的性质，即使外在原因（缺陷、应变或缺陷）不明显。具体而言，打破宏观反转对称性的中心对称相可以支配或显着改变其观察到的属性，而详细的机制和对称性破缺的偏差的幅度往往是模糊的。在这里，我们选择压电作为一种工具，研究宏观反演对称性破缺名义上中心对称材料作为一个突出的例子，并测量共振压电光谱（RPS）和共振超声光谱（罗斯）在15个化合物，18个样品，和21个不同的阶段，包括未极化的铁电体，顺电体，弛豫，铁弹，初期铁电体，以及具有低缺陷浓度的各向同性材料，即，NaCl、熔融石英和CaF 2。我们排除了挠曲电效应作为所观察到的压电性的来源，但在所有名义上的立方相的这些样品中观察到压电性。通过将RPS的强度与罗斯的强度进行标度，我们以单晶石英为标准校准了有效压电系数。使用这个比例，我们确定了名义上非压电相的有效压电模量，发现“禁戒”压电效应的范围从1到10（-5）pm/V（类似于极化铁电锆钛酸铅压电系数的0.5%到2 x 10（-5）%）。未极化铁电相的值仅略高于顺电相的值。极低的系数远低于传统压电测量的检测限，并证明RPS是一种方便和超高灵敏度的方法来测量压电性。我们认为，在名义上的中心对称材料和无序的，未极化的铁电体中，压电破缺是一种常见的现象。
Compound phases often display properties that are symmetry forbidden relative to their nominal, average crystallographic symmetry, even if extrinsic reasons (defects, strain, or imperfections) are not apparent. Specifically, breaking the macroscopic inversion symmetry of a centrosymmetric phase can dominate or significantly change its observed properties while the detailed mechanisms and magnitudes of the deviations of symmetry breaking are often obscure. Here, we choose piezoelectricity as a tool to investigate macroscopic inversion-symmetry breaking in nominally centrosymmetric materials as a prominent example and measure resonant piezoelectric spectroscopy (RPS) and Resonant Ultrasound Spectroscopy (RUS) in 15 compounds, 18 samples, and 21 different phases, including unpoled ferroelectrics, paraelectrics, relaxors, ferroelastics, incipient ferroelectrics, and isotropic materials with low defect concentrations, i.e., NaCl, fused silica, and CaF2. We exclude the flexoelectric effect as a source of the observed piezoelectricity yet observe piezoelectricity in all nominally cubic phases of these samples. By scaling the RPS intensities with those of RUS, we calibrate the effective piezoelectric coefficients using single-crystal quartz as standard. Using this scaling we determine the effective piezoelectric modulus in nominally nonpiezoelectric phases, finding that the "symmetry-forbidden" piezoelectric effect ranges from similar to 1 to 10(-5) pm/V (similar to 0.5% to similar to 2 x 10(-5)% of the piezoelectric coefficient of poled ferroelectric lead zirconate titanate). The values for the unpoled ferroelectric phase are only slightly higher than those in the paraelectric phase. The extremely low coefficients are well below the detection limit of conventional piezoelectric measurements and demonstrate RPS as a convenient and ultrahighly sensitive method to measure piezoelectricity. We suggest that symmetry-breaking piezoelectricity in nominally centrosymmetric materials and disordered, unpoled ferroelectrics is a common phenomenon.