Thermal evolution of polar nanoregions identified by the relaxation time of electric modulus in the Bi
 1/2
 Na
 1/2
 TiO
 3
 system

Liu, Laijun; Ma, Xin; Knapp, Michael; Ehrenberg, Helmut; Peng, Biaolin; Fang, Liang; Hinterstein, Manuel

doi:10.1209/0295-5075/118/47001

Cited by 57 publications

(17 citation statements)

References 43 publications

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“…[8][9][10][11][12] Normally, the high ECE can be achieved in the vicinity of the Curie temperature (T C ) or the polymorphic phase transition (PPT) region with different ferroelectric phases in ferroelectric materials due to the large entropy change. [14][15][16][17][18][19][20][21][22] Recently, some investigations on ECE are also reported in the field of KNN-based materials. By contrast, the PPT region with different ferroelectric phases can be easily obtained near ambient temperature, offering immense potential in practical applications.…”

Section: Introductionmentioning

confidence: 99%

Electrocaloric effect and pyroelectric performance in (K,Na)NbO₃‐based lead‐free ceramics

Yang

Hao

2019

J Am Ceram Soc

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The issue of how to achieve an electrocaloric effect (ECE) and pyroelectric effect in a material simultaneously remains to be a challenge for developing practical solid‐state cooling devices and RF‐detectors. Here, we structure a polymorphic phase transition (PPT) region by doping modification in KNN‐based ceramics, which are developed to achieve the ECE. The direct measured ECE and pyroelectric properties are investigated in lead‐free (1‐x)K0.5Na0.5NbO3‐xBi0.5Na0.5ZrO3 (KNN‐xBNZ) ceramics. The adiabatic temperature change (∆T) of 0.22 K at 100°C, 0.14 K at 70°C and 0.16 K at 30°C can be obtained under an electric field of 35 kV cm–1 for x = 0.03, 0.04 and 0.05, respectively. In addition, the temperature dependence of pyroelectric coefficient (p) is established for all compositions via the Byer‐Roundy method. A large p of 454.46 × 10–4 C m–2 K–1 is detected at Curie temperature (TC) in the ceramics with x = 0.03. Achieving electrocaloric effect and pyroelectric performance simultaneously may shed light and provide a feasible design scheme for developing practically useful electrocaloric and pyroelectric materials.

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Section: Introductionmentioning

confidence: 99%

Electrocaloric effect and pyroelectric performance in (K,Na)NbO₃‐based lead‐free ceramics

Yang

Hao

2019

J Am Ceram Soc

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“…However, the superlattice reflection disappears for the BZT4 composition, and the bifurcated (220) peak gradually transforms into a single symmetric peak, indicating a structural change from the R3c polar phase to the pseudocubic phase. 18,19 Two dielectric anomalies can be observed for all compositions: a frequency-dispersive peak at T s (~110°C) and a rather diffused peak at T m (~240°C). Figure 1A-F display the temperature-dependent dielectric properties of all poled samples in heating/cooling processes to further study the phase transformations.…”

Section: Phase Structure and Microstructurementioning

confidence: 98%

“…[12][13][14][15][16][17] The SEM morphologies show that the synthesized ceramic samples have a highly dense and homogeneous microstructure with relative densities above 95%, and the average grain size is approximately ~0.8 μm ( Figure S2). 3,18,19 Compared with the cooling spectra, an obvious sharp dielectric anomaly is present in the dielectric curves during the heating process. The cooling data can be regarded as that of the unpoled data because the ceramics enter into the paraelectric state upon heating to a sufficiently high temperature.…”

Section: Phase Structure and Microstructurementioning

confidence: 99%

“…Jo et al suggested that the shoulder at T s can be attributed to the thermal evolution of polar-nanoregions (PNRs) with different symmetries, while the broad peak at T m is closely related to the relaxation of high-temperature PNRs. [18][19][20] Nevertheless, the T s peaks on tanδ-T curves are so pronounced that we can use them to estimate the T f . This anomaly with frequency-independent characteristics stems from a temperature-induced ferroelectric (nonergodic)-relaxor (ergodic) transformation; the corresponding temperature can be marked by T FR , where the poling-established polar order reverts to the ergodic relaxor state.…”

Section: Phase Structure and Microstructurementioning

confidence: 99%

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Designing novel sodium bismuth titanate lead‐free incipient perovskite for piezoactuator applications

2019

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Bismuth‐based lead‐free incipient piezoceramics have potential in piezoactuators owing to their large strain response. However, a substantial strain hysteresis and poor temperature/frequency stability heavily restrict their practical applications. Herein, we designed a compositional inhomogeneity and constructed quenched random fields to enhance the relaxor dynamics by introducing a classical relaxor material, Ba(Zr0.2Ti0.8)O3, into a nonergodic material, (Na0.5Bi0.5)TiO3–0.15SrTiO3. Intriguingly, we obtained a large piezoelectric d33∗ coefficient of 602 pm/V and a narrow hysteresis of 32% at the x = 0.04 (BZT4) composition. The strain properties present a robust frequency (~2%, 1‐20 Hz) and temperature stability (~13%, 25‐150°C). The excellent actuating properties of BZT4 were due to a field‐induced reversible ergodic relaxor‐ferroelectric transformation, and the narrow hysteresis can be attributed to quick switching of the dynamic relaxor phase to external stimuli. The origin of the structural transition and salient strain performance was systematically investigated. This study provides a novel route for designing lead‐free incipient perovskite with a large strain, narrow hysteresis and high stability for eco‐friendly actuators.

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“…a dielectric peak as representing a diffuse phase transition (DPT), but the origin of this supposed diffusivity remains controversial, being attributed in some cases to the reorientation of polar nano regions 20,26,34,35 , heterophase fluctuations 31,32 , or defect dipoles originated by oxygen vacancies 30 . Besides, Liu et al have deconvoluted this broad high-temperature dielectric peak in BNT-based materials by using two Gaussian functions, that were associated with the rhombohedral R3c to tetragonal P4bm phase transition and with the clamping of domain walls into the polar regions, induced by oxygen vacancies 36 .…”

mentioning

confidence: 99%

Unveiling the high-temperature dielectric response of $$\text {Bi}_{0.5}\text {Na}_{0.5}\text {TiO}_{3}$$

Diaz

M’Peko

Venet

et al. 2020

Sci Rep

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Understanding the physics behind changes in dielectric permittivity and mechanical response with temperature and frequency in lead-free ferroic materials is a fundamental key to achieve optimal properties and to guarantee good performance in the technological applications envisaged. In this work, dense $$\text {Bi}_{0.5}\text {Na}_{0.5}\text {TiO}_{3}$$ Bi 0.5 Na 0.5 TiO 3 (BNT) electroceramics were prepared through solid-state reaction of high-grade oxide reagents, followed by sintering at high temperature (1393 K for 3 h). In good agreement with previous reports in the literature, the thermal behaviour of dielectric response from these BNT materials showed the occurrence of a high-temperature diffuse-like permittivity peak, whose origin has been so far controversial. Thermally stimulated depolarization current, impedance and mechanical spectroscopies measurements were here conducted, over a wide range of temperature and frequency, to get a deep insight into the mechanism behind of this event. The approach included considering both as-sintered and reduced BNT samples, from which it is demonstrated that the broad high-temperature dielectric peak originates from interfacial polarization involving oxygen vacancies-related space-charge effects that develop at the grain-to-grain contacts. This mechanism, that contributes to the anomalous behavior observed in the mechanical response at low frequencies, could also be responsible for the presence of ferroelastic domains up to high temperatures.

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Thermal evolution of polar nanoregions identified by the relaxation time of electric modulus in the Bi _1/2 Na _1/2 TiO ₃ system

Cited by 57 publications

References 43 publications

Electrocaloric effect and pyroelectric performance in (K,Na)NbO₃‐based lead‐free ceramics

Electrocaloric effect and pyroelectric performance in (K,Na)NbO₃‐based lead‐free ceramics

Designing novel sodium bismuth titanate lead‐free incipient perovskite for piezoactuator applications

Unveiling the high-temperature dielectric response of $$\text {Bi}_{0.5}\text {Na}_{0.5}\text {TiO}_{3}$$

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Thermal evolution of polar nanoregions identified by the relaxation time of electric modulus in the Bi 1/2 Na 1/2 TiO 3 system

Cited by 57 publications

References 43 publications

Electrocaloric effect and pyroelectric performance in (K,Na)NbO3‐based lead‐free ceramics

Electrocaloric effect and pyroelectric performance in (K,Na)NbO3‐based lead‐free ceramics

Designing novel sodium bismuth titanate lead‐free incipient perovskite for piezoactuator applications

Unveiling the high-temperature dielectric response of $$\text {Bi}_{0.5}\text {Na}_{0.5}\text {TiO}_{3}$$

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Thermal evolution of polar nanoregions identified by the relaxation time of electric modulus in the Bi _1/2 Na _1/2 TiO ₃ system

Electrocaloric effect and pyroelectric performance in (K,Na)NbO₃‐based lead‐free ceramics

Electrocaloric effect and pyroelectric performance in (K,Na)NbO₃‐based lead‐free ceramics