Direct and indirect electrocaloric measurements on 〈001〉-PbMg1/3Nb2/3O3-30PbTiO3 single crystals

Goupil, Florian Le; Berenov, A.; Axelsson, Anna‐Karin; Valant, Matjaž; Alford, Neil McN.

doi:10.1063/1.4730338

Cited by 174 publications

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“…The method used to calculate the indirect measurement is given elsewhere. 4 There is a good agreement between both sets of data at high temperature with an increasing trend observed between 130 C and 160 C and the maximum indirect ECE also measured at 160 C. However, the absolute value DT max ¼ 0.57 K, which corresponds to an ECE responsivity of only 0.26 Â 10 À6 K m/V, is significantly lower than that observed by direct measurements. Furthermore, it can be seen that there are significant discrepancies at lower temperatures.…”

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confidence: 64%

“…It can be seen in the inset in the top left corner that there is a reversal of the observed peaks, with an endothermic peak observed upon application of the field and an exothermic observed upon removal, as seen in h001i-PMN-30PT single crystals. 4,25 A negative ECE has also been observed by indirect ECE measurements on NBT, 9 was attributed to the presence of a field-induced phase transition from tetragonal AFE to a more entropic tetragonal FE phase. The negative effect in NBT-18KBT is most likely also due to the presence of a weakly polar phase with different dipolar directions at low applied fields as reported by Viola et al 26 Similar to NBT-BT, 27,28 unpoled ceramics with compositions near the MPB of NBT-KBT show a mixture of R3c and P4bm polar nano-regions.…”

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confidence: 79%

“…Some of the highest ECE performances ever reported were found in the Pb-containing compounds close to their MPB, such as PMN-30PT. 4 The ECE of some lead-free materials with compositions near the CP, such as Zr-doped Ba 0.8 Ca 0.2 TiO 3 , 13 Sn-doped BT, 14 or Sr-doped NBT-BT, 15,16 has also been reported, but very few were studied by direct ECE measurements.…”

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confidence: 99%

“…The direct ECE measurements were performed on the unpoled ceramics with a modified-Differential Scanning Calorimeter (DSC) (Netzsch DSC 200 F3), as described elsewhere. 4 Fig . 1(a) shows the real part of the dielectric permittivity as a function of temperature measured for NBT-18KBT for poled and unpoled ceramics at 10 kHz upon heating.…”

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confidence: 99%

“…This phenomenon is called the ECE. 1 Several materials, both lead-containing, such as Pb(Zr 1Àx Ti x )O 3 (PZT), 2 (1 À x)Pb(Zn 1/3 Nb 2/3 )O 3 -xPbTiO 3 (PZN-PT), 3 or (1 À x)Pb(Mg 1/3 Nb 2/3 )O 3 -xPbTiO 3 (PMNxPT), 4,5 and lead-free, such as BaTiO 3 (BT), 6 Sr x Ba (1Àx) Nb 2 O 3 (SBN), 7,8 or (Na 0.5 Bi 0.5 )TiO 3 (NBT), 9 have been considered for electrocaloric cooling. Lead-free relaxor ferroelectrics (FEs) with high dielectric strength 10 seem highly suitable candidates; however, it is critical to find ways to increase their ECE.…”

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confidence: 99%

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Electrocaloric enhancement near the morphotropic phase boundary in lead-free NBT-KBT ceramics

Goupil

Bennett

Axelsson

et al. 2015

Applied Physics Letters

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117

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confidence: 64%

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confidence: 79%

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confidence: 99%

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confidence: 99%

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Electrocaloric enhancement near the morphotropic phase boundary in lead-free NBT-KBT ceramics

Goupil

Bennett

Axelsson

et al. 2015

Applied Physics Letters

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117

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Giant Electrocaloric Response Over A Broad Temperature Range in Modified BaTiO₃ Ceramics

Qian

Zhang

et al. 2013

Adv Funct Materials

393

261

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1300www.MaterialsViews.com wileyonlinelibrary.com . IntroductionElectrocaloric effect (ECE), an electric fi eld induced temperature and/or entropy change of an insulating material, has attracted a great deal of attention after the recent fi ndings of large ECE in ceramic thin fi lms, polymers, and a dielectric fl uid. [1][2][3][4][5][6][7][8][9][10] Several recent works have also demonstrated potential of realizing high performance cooling devices exploiting large ECE in new electrocaloric (EC) materials. [11][12][13][14] In these newly developed EC materials, the giant ECE, i.e., large adiabatic temperature change Δ T and isothermal entropy change Δ S, were obtained under high applied electrical fi elds. For example, a | Δ T| = 35 K and Δ S = 160 Jkg −1 K −1 were induced in a high energy electron irradiated P(VDFTrFE) relaxor polymer under an electric fi eld change Δ E of 180 MVm −1 . [ 15 ] Analogously, in ferroelectric BaTiO 3 (BT) thick fi lms, a | Δ T| = 7.1 K and Δ S = 10.1 Jkg −1 K −1 were generated under the application of high electric fi elds change Δ E = 80 MVm −1 . [ 16 ] As one starts to address these EC materials for practical cooling devices applications, additional parameters should be considered besides a large Δ T and Δ S to measure the performance of EC materials. For instance, in order for cooling devices to be operated at low voltage such as <200 volts which is the normal voltage range for most cooling devices, an EC material with a large ECE induced under small electric fi elds is also important. In addition, a wide operational temperature range near room temperature is highly desired in order to develop high performance and practical EC cooling devices. [11][12][13][14] Therefore, one critical question is how to design and develop dielectric materials which are capable of generating giant ECE over a broad operation temperature with relatively low applied electric fi eld change Δ E.As a lead-free ferroelectric material which is environmentally friendly and is in fact the most widely used ferroelectric material, ECE in BT has been studied quite extensively in the past several years by many groups and in various forms including thin fi lms, bulk ceramics (including thick fi lms multilayer ceramic capacitors (MLCC)), and single crystals. [16][17][18][19][20][21][22] Large Δ T and Δ S have been reported in BT ceramics at temperatures near the ferroelectric-paraelectric (FE-PE) transition. [ 16 ] It is noted that for BT, besides the high temperature FE-PE transition (the transition temperature T FE-PE > 100 ° C) between the tetragonal ferroelectric (Tet) and cubic paraelectric phase, also exhibits an orthorhombic (O) and a rhombohedral (Rhom) phases as illustrated in Figure 1 (a). [ 23 ] As ECE is directly related to the entropy change of an insulation dielectric under the change of the applied electric fi eld, a dielectric with a polar phase which contains a large number of polar-states with similar energy levels can be induced under a reasonable electric fi eld from a nonpolar phase (i.e., belo...

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Observation of a Negative Thermal Hysteresis in Relaxor Ferroelectric Polymers

Liu

Haibibu

et al. 2020

Adv Funct Materials

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Hysteresis phenomenon including both electrical and thermal types is essential to ferroelectric materials. The former known as polarization-electric field hysteresis has been intensively studied in a wide range of ferroelectric materials. However, relevant experimental evidence on the thermal hysteresis remains limited especially in ferroelectric polymers, even though thermal hysteresis is crucial to the caloric effect which is usually the largest near the phase transition. Here we study the thermal hysteresis behavior in ferroelectric polymers in terms of temperature-dependent polarization upon heating and cooling. In contrast to common belief, we observe a negative thermal hysteresis in relaxor ferroelectric polymers, which is probably due to local stabilization of ferroelectric distortion induced by electric field. Using the polymer blend as a platform, we further show that the negative thermal hysteresis arises at the disappearance of long-range ferroelectric distortion and we may effectively control the thermal hysteresis behavior through the blend This article is protected by copyright. All rights reserved. 2 approach. Our study not only provides deeper insights into electrocaloric effect in ferroelectric polymers but also offers an approach to study the critical phenomenon in a ferroelectric system.

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Direct and indirect electrocaloric measurements on 〈001〉-PbMg1/3Nb2/3O3-30PbTiO3 single crystals

Cited by 174 publications

References 47 publications

Electrocaloric enhancement near the morphotropic phase boundary in lead-free NBT-KBT ceramics

Electrocaloric enhancement near the morphotropic phase boundary in lead-free NBT-KBT ceramics

Giant Electrocaloric Response Over A Broad Temperature Range in Modified BaTiO₃ Ceramics

Observation of a Negative Thermal Hysteresis in Relaxor Ferroelectric Polymers

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Direct and indirect electrocaloric measurements on 〈001〉-PbMg1/3Nb2/3O3-30PbTiO3 single crystals

Cited by 174 publications

References 47 publications

Electrocaloric enhancement near the morphotropic phase boundary in lead-free NBT-KBT ceramics

Electrocaloric enhancement near the morphotropic phase boundary in lead-free NBT-KBT ceramics

Giant Electrocaloric Response Over A Broad Temperature Range in Modified BaTiO3 Ceramics

Observation of a Negative Thermal Hysteresis in Relaxor Ferroelectric Polymers

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Giant Electrocaloric Response Over A Broad Temperature Range in Modified BaTiO₃ Ceramics