The Effect of Composition Gradient on Microdomain Structure and the Macro-Ferroelectric/Piezoelectric Properties

Abstract

Internal fields caused by strain gradient, composition gradient (CG), and space charges have significant influences on micro and macro properties of ferroelectrics. Here, we report the relationship among composition gradient, microdomain structure, and macroscopic ferroelectric/piezoelectric properties. Three KTa1–x Nb x O3 samples with the same Curie temperature T c = 39 °C and different CGs are designed and investigated. As CG decreases, the scale of domains decreases from ∼10 μm to 200 nm, and the spontaneous polarizations orientate more randomly, which leads to a smaller ratio of lattice content c to a (c/a). Furthermore, dielectric constant and d 33 increases dramatically from 6000 to 11 000 and from 203 to 345 pC N–1, respectively. This relationship is important for prospective applications due to its controllability of microdomains and polarization states. In addition, we reveal that CG and composition fluctuation induce internal fields (E in) and resilience, respectively, leading to the frequency-dependent biased and standard double polarization–electric field (P–E) loops. Moreover, the existence of CGs drives the formation of different size domains by E in, which provides a way to adjust ferroelectric and piezoelectric properties by controlling CG. As well, it is important for the study of flexoelectric on continuous CG bulk materials.

Low DC Electric-Field-Induced Phase Transition in KTa0.59Nb0.41O3 Crystal

“…The DC electric-field-induced P C−T also can be distinguished by this way, because ferroelectric domain is a typical feature of the ferroelectric phase for KTN crystals. Such domain (90°d omain) structures, to minimize the free energy associated with polarization charge, 41 can be attributed to the great grain size of a sample; 42 and these domain structures are also observed in the process of temperature-induced phase transition, which was measured by Huang et al 43 In addition, the E−T phase diagram (as shown in Figure 6b) is obtained from Figure 6a. The E−T phase diagram shows the close to linear variation of phase transition electric field with the temperature in the whole measured temperature range and the expression of the linear variation is E = 0.6T − 185.2, which is consistent with the result obtained by Khemakhem et al 44 And we see that because of the linear variation, the critical electric field of P C−T shifts to higher value as temperature increases.…”

Inverse Design of Ferroelectric‐Order in Perovskite Crystal for Self‐Powered Ultraviolet Photodetection

“…Under low frequency, KTN displays a normal P-E loop with an apparent remanent polarization value. [23,24] The origin of double-loop hysteresis should be more possibly attributed to the recoverable reorientation of the asymmetric polar domains induced by the component gradient of Ta/Nb. To understand the relationship between ferroelectric order and photoelectric response, we fabricated KTN-based photodetectors with cubic KTN1 and tetragonal KTN2, KTN3, and KTN4 crystals.…”

Enhanced Electrocaloric Effect Induced by the Electric-Field-Generated Like-Multiphase Coexistence in Anisotropic KTa1–xNbxO3 Single Crystals

“…Potassium tantalum niobate (KTa 1– x Nb x O 3 , KTN) single crystals possess excellent optical − and ferroelectric − properties. As a first-order phase transition (FPT) ferroelectric, KTN has been proven to exhibit an EC performance. , For example, KTN modified with Li + gave rise to a large EC property of Δ T ∼ 0.42 K (under 20 kV cm –1 ).…”