Electrocaloric Effect of (K1−xNax)NbO3 Single Crystal

2021 ◽  
Vol 21 (10) ◽  
pp. 5378-5381
Author(s):  
MinYa Jin ◽  
JianHua Qiu ◽  
ZhiHui Chen ◽  
XiuQin Wang ◽  
NingYi Yuan ◽  
...  
Keyword(s):  
Single Crystal ◽  
Temperature Change ◽  
Tetragonal Phase ◽  
Room Temperature ◽  
Ferroelectric Phase ◽  
Orthorhombic Phase ◽  
Adiabatic Temperature ◽  
Electrocaloric Effect ◽  
Adiabatic Temperature Change ◽  
Experimental Findings

The electrocaloric effect of (K1−xNax)NbO3 single crystal is calculated based on Landau-Devonshire theory. The electrocaloric coefficient and adiabatic temperature change are calculated with the variation of temperature in rhombohedral, orthorhombic and tetragonal phase. A maximum of electrocaloric coefficient is obtained in each ferroelectric phase. Moreover, the tetragonal phase presents the larger electrocaloric coefficient and adiabatic temperature change than that rhombohedral and orthorhombic phase. However, the large electrocaloric effect is also obtained at room temperature with the adiabatic temperature change of 0.5 K, which tallies with the experimental findings.

The Electrocaloric Effect in BaTiO3 Thick Film Multilayer Structure at High Electric Field

2012 ◽  
Vol 512-515 ◽  
pp. 1304-1307 ◽  
Author(s):  
Yang Bai ◽  
Kai Ding ◽  
Guang Ping Zheng ◽  
San Qiang Shi ◽  
Lie Jie Qiao ◽  
...  
Keyword(s):  
Electric Field ◽  
Thick Film ◽  
Temperature Change ◽  
Multilayer Structure ◽  
Tape Casting ◽  
Adiabatic Temperature ◽  
Ferroelectric Ceramics ◽  
Heat Absorption ◽  
Electrocaloric Effect ◽  
Adiabatic Temperature Change

We demonstrated the superior electrocaloric effect (ECE) in BaTiO3 multilayer structure. The sample fabricated by tape-casting process has 120 effective ferroelectric layers with average layer thickness of 1.7 μm. The ferroelectric hysteresis loops were measured in the temperature range from 30 to 180 oC, and then the temperature dependences of ECE adiabatic temperature change and heat absorption were obtained according to Maxwell relation. A peak ECE adiabatic temperature change of 0.027 K/V and heat absorption of 0.36 J/g were observed near the ferroelectric phase transition at 125 oC under Vmax=25 V. The BaTiO3 thick film can sustain an external electric field (>500 kV/cm) several times higher than bulk ferroelectric ceramics (~30 kV/cm). Although the EC coefficient of BaTiO3 is much lower than lead-based ferroelectric ceramics, the ultrahigh working electric field endows it a large ECE, higher than that of most reported lead-based ferroelectric ceramics. In addition, the lead-free composition provides it a promising future in solid-state cooling technology.

Ultrahigh room temperature electrocaloric response in lead-free bulk ceramicsviatape casting

2019 ◽  
Vol 7 (23) ◽  
pp. 6860-6866 ◽  
Author(s):  
Hongliang Du ◽  
Yunfei Chang ◽  
Chunwang Li ◽  
Qingyuan Hu ◽  
Jing Pang ◽  
...  
Keyword(s):  
Temperature Change ◽  
Room Temperature ◽  
Tape Casting ◽  
Adiabatic Temperature ◽  
Lead Free ◽  
Casting Technique ◽  
Bulk Ceramic ◽  
Adiabatic Temperature Change ◽  
Giant Step

An ultrahigh room temperature adiabatic temperature change (∼1.6 K) was realized in a BaTiO3-based bulk ceramic prepared by the tape casting technique, which makes a giant step-forward for electrocaloric refrigeration.

scholarly journals Old Donors for New Molecular Conductors: Combining TMTSF and BEDT-TTF with Anionic (TaF6)1−x/(PF6)x Alloys

Crystals ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 386
Author(s):  
Magali Allain ◽  
Cécile Mézière ◽  
Pascale Auban-Senzier ◽  
Narcis Avarvari
Keyword(s):  
Single Crystal ◽  
Room Temperature ◽  
Density Wave ◽  
Spin Density Wave ◽  
Orthorhombic Phase ◽  
Molecular Conductors ◽  
Bechgaard Salts ◽  
Temperature Conductivity ◽  
Room Temperature Conductivity ◽  
Resistivity Measurements

Tetramethyl-tetraselenafulvalene (TMTSF) and bis(ethylenedithio)-tetrathiafulvalene (BEDT-TTF) are flagship precursors in the field of molecular (super)conductors. The electrocrystallization of these donors in the presence of (n-Bu4N)TaF6 or mixtures of (n-Bu4N)TaF6 and (n-Bu4N)PF6 provided Bechgaard salts formulated as (TMTSF)2(TaF6)0.84(PF6)0.16, (TMTSF)2(TaF6)0.56(PF6)0.44, (TMTSF)2(TaF6)0.44(PF6)0.56 and (TMTSF)2(TaF6)0.12(PF6)0.88, together with the monoclinic and orthorhombic phases δm-(BEDT-TTF)2(TaF6)0.94(PF6)0.06 and δo-(BEDT-TTF)2(TaF6)0.43(PF6)0.57, respectively. The use of BEDT-TTF and a mixture of (n-Bu4N)TaF6/TaF5 afforded the 1:1 phase (BEDT-TTF)2(TaF6)2·CH2Cl2. The precise Ta/P ratio in the alloys has been determined by an accurate single crystal X-ray data analysis and was corroborated with solution 19F NMR measurements. In the previously unknown crystalline phase (BEDT-TTF)2(TaF6)2·CH2Cl2 the donors organize in dimers interacting laterally yet no organic-inorganic segregation is observed. Single crystal resistivity measurements on the TMTSF based materials show typical behavior of the Bechgaard phases with room temperature conductivity σ ≈ 100 S/cm and localization below 12 K indicative of a spin density wave transition. The orthorhombic phase δo-(BEDT-TTF)2(TaF6)0.43(PF6)0.57 is semiconducting with the room temperature conductivity estimated to be σ ≈ 0.16–0.5 S/cm while the compound (BEDT-TTF)2(TaF6)2·CH2Cl2 is also a semiconductor, yet with a much lower room temperature conductivity value of 0.001 to 0.0025 S/cm, in agreement with the +1 oxidation state and strong dimerization of the donors.

Large electrocaloric response with superior temperature stability in NaNbO3-based relaxor ferroelectrics benefiting from crossover region

2020 ◽  
Author(s):  
Ling Zhang ◽  
Chunlin Zhao ◽  
Ting Zheng ◽  
Jiagang Wu
Keyword(s):  
Temperature Change ◽  
Temperature Stability ◽  
Relaxor Ferroelectrics ◽  
Adiabatic Temperature ◽  
Next Generation ◽  
Crossover Region ◽  
Adiabatic Temperature Change

Electrocaloric refrigeration emerges as a newly-developing technology with potential to be the next generation of coolers. However, the combination of large adiabatic temperature change (ΔT) and good temperature stability remains...

scholarly journals Tunable Magnetocaloric Properties of Gd-Based Alloys by Adding Tb and Doping Fe Elements

Materials ◽  
2019 ◽  
Vol 12 (18) ◽  
pp. 2877 ◽  
Author(s):  
Lingfeng Xu ◽  
Chengyuan Qian ◽  
Yongchang Ai ◽  
Tong Su ◽  
Xueling Hou
Keyword(s):  
Magnetic Field ◽  
Curie Temperature ◽  
Temperature Change ◽  
Indirect Measurement ◽  
Adiabatic Temperature ◽  
Doping Content ◽  
Adiabatic Temperature Change ◽  
Magnetocaloric Properties ◽  
Capacity Calculation ◽  
Low Magnetic Field

In this paper, the magnetocaloric properties of Gd1−xTbx alloys were studied and the optimum composition was determined to be Gd0.73Tb0.27. On the basis of Gd0.73Tb0.27, the influence of different Fe-doping content was discussed and the effect of heat treatment was also investigated. The adiabatic temperature change (ΔTad) obtained by the direct measurement method (under a low magnetic field of 1.2 T) and specific heat capacity calculation method (indirect measurement) was used to characterize the magnetocaloric properties of Gd1−xTbx (x = 0~0.4) and (Gd0.73Tb0.27)1−yFey (y = 0~0.15), and the isothermal magnetic entropy (ΔSM) was also used as a reference parameter for evaluating the magnetocaloric properties of samples together with ΔTad. In Gd1−xTbx alloys, the Curie temperature (Tc) decreased from 293 K (x = 0) to 257 K (x = 0.4) with increasing Tb content, and the Gd0.73Tb0.27 alloy obtained the best adiabatic temperature change, which was ~3.5 K in a magnetic field up to 1.2 T (Tc = 276 K). When the doping content of Fe increased from y = 0 to y = 0.15, the Tc of (Gd0.73Tb0.27)1−yFey (y = 0~0.15) alloys increased significantly from 276 K (y = 0) to 281 K (y = 0.15), and a good magnetocaloric effect was maintained. The annealing of alloys (Gd0.73Tb0.27)1−yFey (y = 0~0.15) at 1073 K for 10 h resulted in an average increase of 0.3 K in the maximum adiabatic temperature change and a slight increase in Tc. This study is of great significance for the study of magnetic refrigeration materials with adjustable Curie temperature in a low magnetic field.

scholarly journals Dynamics of the magnetoelastic phase transition and adiabatic temperature change in Mn1.3Fe0.7P0.5Si0.55

2019 ◽  
Vol 477 ◽  
pp. 287-291 ◽  
Author(s):  
M. Fries ◽  
T. Gottschall ◽  
F. Scheibel ◽  
L. Pfeuffer ◽  
K.P. Skokov ◽  
...  
Keyword(s):  
Phase Transition ◽  
Temperature Change ◽  
Adiabatic Temperature ◽  
Adiabatic Temperature Change
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