Affiliations 

  • 1 Department of Mechanical and Aerospace Engineering, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong
  • 2 Department of Chemistry, South University of Science and Technology of China, Shenzhen, 518055, China. huanglm@sustc.edu.cn
  • 3 School of Engineering, Monash University Malaysia, Bandar Sunway, 46150, Malaysia
  • 4 Department of Mechanical and Aerospace Engineering, Rutgers University, New Brunswick, New Jersey, 08903, USA
  • 5 Chongqing Institute of Green & Intelligent Technology, Chinese Academy of Sciences, Chongqing, 400714, China
  • 6 Center for High Pressure Science and Technology Advanced Research, Shanghai, 201203, China
Sci Rep, 2017 09 11;7(1):11111.
PMID: 28894256 DOI: 10.1038/s41598-017-11633-y

Abstract

Electrocaloric (EC) materials show promise in eco-friendly solid-state refrigeration and integrable on-chip thermal management. While direct measurement of EC thin-films still remains challenging, a generic theoretical framework for quantifying the cooling properties of rich EC materials including normal-, relaxor-, organic- and anti-ferroelectrics is imperative for exploiting new flexible and room-temperature cooling alternatives. Here, we present a versatile theory that combines Master equation with Maxwell relations and analytically relates the macroscopic cooling responses in EC materials with the intrinsic diffuseness of phase transitions and correlation characteristics. Under increased electric fields, both EC entropy and adiabatic temperature changes increase quadratically initially, followed by further linear growth and eventual gradual saturation. The upper bound of entropy change (∆Smax) is limited by distinct correlation volumes (V cr ) and transition diffuseness. The linearity between V cr and the transition diffuseness is emphasized, while ∆Smax = 300 kJ/(K.m3) is obtained for Pb0.8Ba0.2ZrO3. The ∆Smax in antiferroelectric Pb0.95Zr0.05TiO3, Pb0.8Ba0.2ZrO3 and polymeric ferroelectrics scales proportionally with V cr-2.2, owing to the one-dimensional structural constraint on lattice-scale depolarization dynamics; whereas ∆Smax in relaxor and normal ferroelectrics scales as ∆Smax ~ V cr-0.37, which tallies with a dipolar interaction exponent of 2/3 in EC materials and the well-proven fractional dimensionality of 2.5 for ferroelectric domain walls.

* Title and MeSH Headings from MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.