X-ray studies of electrocaloric lead-scandium tantalate ordered solid solutions

Shebanov, L. A.; Birks, E.; Borman, K.

doi:10.1080/00150198908211286

Cited by 31 publications

(17 citation statements)

References 2 publications

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“…The four bipolar plots show that the ferroelectric loop at 280 K became a double loop 41 over a limited range of temperatures above T C , evidencing the field-driven transition in PST (ref. 36). However, we will use our unipolar plots in what follows because the field hysteresis is smaller.…”

Section: Resultsmentioning

confidence: 99%

Electrocaloric Cooling Cycles in Lead Scandium Tantalate with True Regeneration via Field Variation

et al. 2019

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There is growing interest in heat pumps based on materials that show thermal changes when phase transitions are driven by changes of electric, magnetic or stress field. Importantly, regeneration permits sinks and loads to be thermally separated by many times the changes of temperature that can arise in the materials themselves. However, performance and parameterization are compromised by net heat transfer between caloric working bodies and heat-transfer fluids. Here we show that this net transfer can be avoided-resulting in true, balanced regeneration-if one varies the applied electric field while an electrocaloric (EC) working body dumps heat on traversing a passive fluid regenerator. Our EC working body is represented by bulk PbSc 0.5 Ta 0.5 O 3 (PST) near its first-order ferroelectric phase transition, where we record directly measured adiabatic temperature changes of up to 2.2 K. Indirectly measured adiabatic temperature changes of similar magnitude were identified, unlike normal, from adiabatic measurements of polarization, at nearby starting passive regeneration, this net transfer has been noted explicitly in a seminal paper 1 , and elsewhere 22 .The key figure of merit for any cooling device is its coefficient of performance COP = Q/W, where in each cooling cycle, work W is done to pump heat Q from a cold load at T c towards a hot sink at T h . The effect of the net-transfer problem is to partially subsume regenerators into sinks or loads, with two consequences. First and foremost, it becomes impossible to realize intended cooling cycles, thus compromising device COPs. Second, the active material undergoes net heat exchange at temperatures lying away from T c and T h , thus compromising the calculation of the Carnot limit T c /(T h -T c ) from measured values of T c and T h . Given that COPs and Carnot limits are thus compromised, it immediately follows that device efficiencies are neither optimized nor accurate (efficiency = COP/Carnot). To solve the nettransfer problem, we will construct valid cooling cycles on detailed field-temperature-entropy maps, and we will accurately evaluate the resulting COPs, Carnot limits and efficiencies.These parameters contrast with COPs for materials in isothermal cycles 23 , and the related parameter of materials efficiency 24 that describes reversible caloric transitions driven isothermally in just one direction.The net-transfer problem has been hitherto masked in EC cooling cycles because the zerofield and finite-field isofields are rendered parallel by assuming peak performance at all points in any given cycle [25][26][27] . However, even for relaxors that show large EC effects over wide ranges of temperatures 6,20,21 , this assumption is only reasonable for small temperature spans T h -T c that would only be useful when exploiting converse EC effects for pyroelectric energy harvesting 28 . The net-transfer problem has also been masked in cooling cycles based on mC materials, either by likewise assuming peak performance 29 or by assuming isothermal conditions 23 . In t...

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Section: Resultsmentioning

confidence: 99%

Electrocaloric Cooling Cycles in Lead Scandium Tantalate with True Regeneration via Field Variation

et al. 2019

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“…3) Following his study, many ceramic materials were studied such as SrTiO 3 4) and KTaO 3 ,5) the antiferroelectric Pb(Zr,Ti)O 3 , 6) and the ferroelectrics Roshelle salt, 3) KH 2 PO 4 , 7) BaTiO 3 , 8) TGS, 9) Pb(Zr,Ti)O 3 , 6,10) Pb(Sc,Ta)O 3 , [11][12][13][14] and Pb(Mg,Nb)O 3 -PbTiO 3 . [15][16][17] However, these temperature changes were smaller than 2.5 K. 18) In 2006, Mischenko et al suggested that a much larger ΔT appears near the para=ferro critical point.…”

Section: Introductionmentioning

confidence: 99%

Thermodynamic analysis of a cooling system using electrocaloric effect

Honmi

Hashizume

Nakajima

et al. 2017

Jpn. J. Appl. Phys.

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A cooling system using the electrocaloric effect is investigated on the bases of the thermodynamic theory. The electrocaloric effect causes a temperature change of dielectric materials. In this study, we introduce a simple model of the cooling system including a target object, a heat removal body, and a dielectric material. We confirm that the temperature of the target object certainly decreases. Furthermore, we propose an efficient control procedure of the electric field for cooling the target object. As a result, we show that the temperature change is enhanced by the proposed method.

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“…[229][230][231] [232,233] The "cationordered" phase where the Sc and Ta ions are each arranged in alternating B-site positions throughout the lattice behaves as an ordinary FE with a first-order paraelectric-FE phase transition at ≈295 K. [234] On the other hand, the "cation-disordered" phase can behave as a relaxor FE. [106,235,236] The degree of ordering in PST is defined by the long-range order parameter Ω given by Ω = 2n − 1 where n is the occupation number of the Sc atoms in the B sites. The critical temperature T C where the dielectric constant is at a maximum in PST is dependent on the long-range order parameter with T C = 311 K for Ω = 0 to T C = 323 K for Ω = 0.94.…”

Section: Pst-based Ceramics and Thin Filmsmentioning

confidence: 99%

“…Lead scandium niobate, Pb(Sc 0.5 Nb 0.5 )O 3 (PSN) also has a A(B x B′ 1−x )O 3 type complex perovskite structure (similar to PST) where the degree of ordering between Sc 3+ and Nb 4+ ions in B sites is determined by the thermal prehistory of the material. [106,233,238] When processed in a manner that does not suppress lead vacancies, they exhibit normal relaxor FE behavior. However, if stoichiometry is controlled, disordered PSN transforms spontaneously from a relaxor into a normal FE upon cooling.…”

Section: Psn-based Ceramicsmentioning

confidence: 99%

“…[100] In 1968, EC effects (|ΔT| = 1.6 K at |ΔE| = 30 kV cm −1 at 317 K) were reported in various doped and undoped PbZr x Ti 1−x O 3 (PZT) materials. [101] In the next decades, EC effects were reported in several FE perovskite ceramics such as KTaO 3 , [102] Pb(Zr,Sn,Ti)O 3 (PZST), [103,104] Pb(Sc,Nb)O 3 (PSN), [105] Pb(Sc,Ti)O 3 (PST), [106] and Pb(Mg,Nb)O 3 (PMN). [107] However, studies in bulk materials were limited to |ΔT| < 2 K at best in response to |ΔE| < 50 kV cm −1 .…”

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Caloric Effects in Perovskite Oxides

Barman

Kar‐Narayan

Mukherjee

2019

Adv Materials Inter

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Perovskite oxides show an amazing diversity of electronic and magnetic properties along with a myriad of structural variants and phase transitions. Large thermal changes may be driven near the ferroic phase transitions in perovskite oxides using magnetic, electric, and stress fields to manipulate conjugate order parameters. The ensuing magnetocaloric, electrocaloric, and mechanocaloric effects can be utilized for environment‐friendly and high‐efficiency solid‐state cooling applications. In this review the details of these caloric effects in perovskite oxides both from a chronological perspective and from the viewpoint of the recent advances in multiple caloric phenomena are described. The authors highlight the role of interfaces in oxide thin films for the different caloric effects and address some of the outstanding challenges for the fundamental understanding and practical implementation of perovskite oxides in solid state refrigeration.

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X-ray studies of electrocaloric lead-scandium tantalate ordered solid solutions

Cited by 31 publications

References 2 publications

Electrocaloric Cooling Cycles in Lead Scandium Tantalate with True Regeneration via Field Variation

Electrocaloric Cooling Cycles in Lead Scandium Tantalate with True Regeneration via Field Variation

Thermodynamic analysis of a cooling system using electrocaloric effect

Caloric Effects in Perovskite Oxides

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