Maxwell relation, giant (negative) electrocaloric effect, and polarization hysteresis

The electrocaloric effect (ECE) in dielectrics is characterized by the isothermal entropy change ΔS and adiabatic temperature change ΔT induced by changes of external electric fields. The Maxwell relation, which relates changes of polarization P with temperature T (pyroelectric coefficient) under a fixed electric field E to ΔS for finite intervals in E, provides a convenient way to deduce the ECE from polarization data P(T, E). Hence, this method, known as the indirect method, is widely used in ECE studies in ferroelectrics. Here, we first present the thermodynamic consideration for the Maxwell relation. We then use the indirect method and P(T, E) from bipolar and unipolar polarization curves to deduce the ECE in the normal ferroelectric phase of a P(VDF-TrFE) copolymer. The deduced ECE using the P(T, E) from bipolar polarization curves exhibits a giant negative ECE. In contrast, the directly measured ECE in the same polymer shows the weak and normal ECE. We discuss the constraints of the indirect method and its relation to the polarization-electric field curves measured in practical ferroelectric materials.

This article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing. This article appeared in Appl. Phys. Lett. 118, 122904 (2021) and may be found at https://doi.org/10.1063/5.0042333

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Work Title Maxwell relation, giant (negative) electrocaloric effect, and polarization hysteresis
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Open Access
Creators
  1. Xin Chen
  2. Siqi Li
  3. Xiaodong Jian
  4. Yusra Hambal
  5. Sheng Guo Lu
  6. Vladimir V. Shvartsman
  7. Doru C. Lupascu
  8. Q. M. Zhang
License In Copyright (Rights Reserved)
Work Type Article
Publisher
  1. Applied Physics Letters
Publication Date March 23, 2021
Publisher Identifier (DOI)
  1. https://doi.org/10.1063/5.0042333
Deposited December 10, 2021

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  • Added Maxwell_Relation__Giant__Negative__Electrocaloric_Effect__and_Polarization_Hysteresis.docx
  • Added Creator Xin Chen
  • Added Creator Siqi Li
  • Added Creator Xiaodong Jian
  • Added Creator Yusra Hambal
  • Added Creator Sheng Guo Lu
  • Added Creator Vladimir V. Shvartsman
  • Added Creator Doru C. Lupascu
  • Added Creator Q. M. Zhang
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