Ferroelectric precursor behavior in PbSc 0.5 Ta 0.5 O 3 detected by field-induced resonant piezoelectric spectroscopy
Ferroelectric precursor behavior in PbSc 0.5 Ta 0.5 O 3 detected by field-induced resonant piezoelectric spectroscopy
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场致谐振压电光谱检测 PbSc 0.5 Ta 0.5 O 3 中的铁电前驱体行为
DOI：
10.1103/physrevb.88.174112
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发表时间：
2013
影响因子：
3.7
通讯作者：
Aktas O
中科院分区：
文献类型：
--
作者：
Aktas O
一种新颖的实验技术，共振压电光谱（RPS），已被应用于研究高（65）B位有序PbScTaO（PST）中的极性前体效应，该材料在300 K附近经历铁电相变。立方-菱面体相变是弱一阶，共存间隔为4 K，并伴随着显着的弹性异常 在很宽的温度区间内。立方相中的前驱体极性被检测为由频率范围 250-710 kHz 的局部压电激励产生的弹性振动。 RPS 共振频率完全遵循传统共振超声光谱 (RUS) 产生的弹性共振频率，但加热到超过 425 K 的起始温度时，RPS 信号消失。如果前体状态中的 PST 结构在与转变点 K 之间具有局部极对称性，即使它保持宏观立方体，则可以理解 RPS 和 RUS 响应之间的差异。有人提出，这种前驱行为可能涉及由应变和多阶参数之间的耦合产生的花呢微观结构的发展，这可以从朗道理论的角度来理解。作为温度的函数，转变由极位移和晶体 B 位点上阳离子排序的有序参数驱动。文献中的结果表明，作为压力的函数，存在由八面体倾斜驱动的单独的不稳定性，其指定的阶次参数是。两个主要位移有序参数 和 ，通过双二次项不利地耦合，并且前驱体中复杂的花呢状波动预计会结合所有有序参数的各个方面。这与极性纳米区域的发展不同，极性纳米区域通常被用来解释弛豫铁电行为，例如在 B 位有序度较低的 PST 中发生的情况。
A novel experimental technique, resonant piezoelectric spectroscopy (RPS), has been applied to investigate polar precursor effects in highly (65) B-site ordered PbScTaO(PST), which undergoes a ferroelectric phase transition near 300 K. The cubic-rhombohedral transition is weakly first order, with a coexistence interval of4 K, and is accompanied by a significant elastic anomaly over a wide temperature interval. Precursor polarity in the cubic phase was detected as elastic vibrations generated by local piezoelectric excitations in the frequency range 250–710 kHz. The RPS resonance frequencies follow exactly the frequencies of elastic resonances generated by conventional resonant ultrasound spectroscopy (RUS) but RPS signals disappear on heating beyond an onset temperature,, of 425 K. Differences between the RPS and RUS responses can be understood if the PST structure in the precursor regime betweenand the transition point,K, has locally polar symmetry even while it remains macroscopically cubic. It is proposed that this precursor behavior could involve the development of a tweed microstructure arising by coupling between strain and multiple order parameters, which can be understood from the perspective of Landau theory. As a function of temperature the transition is driven by the polar displacementand the order parameter for cation ordering on the crystallographic B site. Results in the literature show that, as a function of pressure, there is a separate instability driven by octahedral tilting for which the assigned order parameter is. The two mainly displacive order parameters,and, are unfavorably coupled via a biquadratic term, and complex tweedlike fluctuations in the precursor regime would be expected to combine aspects of all the order parameters. This would be different from the development of polar nanoregions, which are more usually evoked to explain relaxor ferroelectric behavior, such as occurs in PST with a lower degree of B-site order.