Improvement of piezoelectric properties is always a key issue in the research of piezoelectric materials. The construction of component gradient (CG) is a novel method to improve piezoelectric properties. However,...
(K, Na)NbO3-based materials exhibit a high potential for applications in electronic devices. Generally, to improve the piezoelectric properties to meet the requirements of applications, a polymorphic phase transition boundary is...
High-performance electro-optic (EO) crystals play a key role in optical communication and information processing. Potassium tantalate niobate (KTa1−xNbxO3, KTN) crystals advantageously have an ultrahigh quadratic electro-optic (QEO) coefficient and a wide transparency range, and their excellent QEO properties are closely related to polar nanoregion (PNR)-related polar units. Owing to the PNR-related polar units, KTN crystals have excellent strain properties, which makes them a potential multifunctional material. However, the relationship between strain behavior and QEO properties in nanodisordered KTN crystals has rarely been reported. The promotion of EO activity by regulating the PNRs-related polar units still needs to be studied. Here, we study the coupling effect of strain behavior and QEO properties in KTN crystals. The QEO, elastic-optic, electrostrictive, and elastic coefficients of KTN crystals are characterized, and the strain–QEO property coupling relation is established. The results show that the strain-induced QEO response significantly affects the QEO properties. The existence and response of PNRs near ferroelectric–paraelectric phase transition are demonstrated by variable-temperature x-ray diffraction and Raman spectroscopy. Combined with the heating and cooling QEO response time tests, the response of PNRs is shown to be an important reason for the enhancement of the QEO response of KTN crystals through the promotion of the strain-induced QEO response. This study provides guidance for clarifying the origin of the QEO properties of nanodisordered KTN crystals and is beneficial for further improving the EO properties of perovskite crystals by manipulating the strain behavior.
The origin of the excellent properties of KTN‐based materials around Curie temperature (TC), which should be originated form the motion of polar nanoregions (PNRs), has attracted considerable research interest. In this paper, the relaxation of a KTa0.63Nb0.37O3 single crystal is discussed with the temperature dependence of permittivity. Moreover, its pyroelectric effect above TC is investigated. In detail, the pyroelectric coefficient decreases from ∼110.0 to ∼13.0 μC/(m2 K), with the temperature increasing from 22 to 33°C, and finally reduces to 0 at 100°C with PNRs disappear. Moreover, the dynamic dielectric nonlinearity for the KTN single crystal is studied in the paraelectric phase. To investigate these mechanisms, the amplitude and phase angle of the first and third harmonics under various electric fields, frequencies, and temperatures are analyzed. As a result, the motions of PNRs induced by electric field, which is pinned and depinned by the defect, are presented to explain the nonlinear dielectric response observed in the paraelectric KTN single crystal.
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