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The Ignored Effects of Vibrational Entropy and Electrocaloric Effect in PbTiO 3 and PbZr 0.5Ti 0.5O 3 as Studied Through First-Principles Calculation

28 Pages Posted: 16 Oct 2019 First Look: Under Review

See all articles by Chenhan Liu

Chenhan Liu

Southeast University (China) - Jiangsu Key Laboratory for Design and Manufacture of Micro-Nano Biomedical Instruments; University of California, Berkeley - Department of Mechanical Engineering

Wei Si

Southeast University (China) - Jiangsu Key Laboratory for Design and Manufacture of Micro-Nano Biomedical Instruments

Chao Wu

Southeast University (China) - Jiangsu Key Laboratory for Design and Manufacture of Micro-Nano Biomedical Instruments

Juekuan Yang

Southeast University (China) - Jiangsu Key Laboratory for Design and Manufacture of Micro-Nano Biomedical Instruments

Yunfei Chen

Southeast University (China) - Jiangsu Key Laboratory for Design and Manufacture of Micro-Nano Biomedical Instruments

Chris Dames

University of California, Berkeley - Department of Mechanical Engineering

Abstract

In an isothermal process, applying an electric field E to a ferroelectric material can change its entropy S through two distinct mechanisms: namely, through changing the dipole alignment or configurational entropy (ΔSconf), and the vibrational entropy due to the intrinsic structure response (ΔSvib). Previous numerical investigations yield only the total entropy change ΔS but cannot separate these two contributions. Here we develop a full first-principles method to extract ΔSvib and the corresponding induced adiabatic temperature change ΔTvib under E, i.e. the electrocaloric effect (ECE), and compare them to the total ΔS and ΔT from molecular dynamics simulation based on a first-principles effective Hamiltonian model. For both single crystal PbTiO3 (PTO) and PbZr0.5Ti0.5O3 (50/50 PZT), the calculation results show that for T far from the phase transition temperature Tpt, ΔSvib plays an important and even dominant role in the ECE. On the other hand, for T close to Tpt, ΔSconf dominates the ECE. Moreover, for PTO, we find that positive E can cause positive ECE, while negative E cause negative ECE. Therefore, by combining both positive and negative ECE in a "bipolar" Ericsson cycle, the cooling energy density can significantly increase as compared to that of a unipolar cycle.

Keywords: first-principles calculation, ferroelectric materials, electrocaloric cooling, entropy change

Suggested Citation

Liu, Chenhan and Si, Wei and Wu, Chao and Yang, Juekuan and Chen, Yunfei and Dames, Chris, The Ignored Effects of Vibrational Entropy and Electrocaloric Effect in PbTiO 3 and PbZr 0.5Ti 0.5O 3 as Studied Through First-Principles Calculation. Available at SSRN: https://ssrn.com/abstract=3467755

Chenhan Liu (Contact Author)

Southeast University (China) - Jiangsu Key Laboratory for Design and Manufacture of Micro-Nano Biomedical Instruments ( email )

China

University of California, Berkeley - Department of Mechanical Engineering ( email )

Berkeley, CA 94720-1740
United States

Wei Si

Southeast University (China) - Jiangsu Key Laboratory for Design and Manufacture of Micro-Nano Biomedical Instruments

China

Chao Wu

Southeast University (China) - Jiangsu Key Laboratory for Design and Manufacture of Micro-Nano Biomedical Instruments

China

Juekuan Yang

Southeast University (China) - Jiangsu Key Laboratory for Design and Manufacture of Micro-Nano Biomedical Instruments

China

Yunfei Chen

Southeast University (China) - Jiangsu Key Laboratory for Design and Manufacture of Micro-Nano Biomedical Instruments ( email )

China

Chris Dames

University of California, Berkeley - Department of Mechanical Engineering ( email )

Berkeley, CA 94720-1740
United States

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