TY - JOUR
T1 - Modeling of enhanced electrocaloric effect above the Curie temperature in relaxor ferroelectrics
AU - Shi, Y. P.
AU - Soh, A. K.
N1 - Funding Information:
Research Grants Council of the Hong Kong Special Administrative Region, under Project No. HKU 716508E, is acknowledged. We would like to thank Professor Huajian Gao at Brown university for his thought-provoking comments and discussion.
Copyright:
Copyright 2011 Elsevier B.V., All rights reserved.
PY - 2011/8
Y1 - 2011/8
N2 - The electrocaloric (EC) effect offers promise as a means to realize solid-state refrigeration, which requires EC materials possessing a pronounced pyroelectric effect over a broad temperature range. Pauli's master equation is adopted to investigate the recently observed phenomenon of enhanced EC effect above the Curie temperature in relaxor ferroelectrics. The proposed approach allows the EC coefficient to be determined within the framework of classic Landau-Ginzburg-Devonshire thermodynamics and the Maxwell relation, taking into account both the depolarization effect and dielectric permittivity dispersion based on the concept of superparaelectricity and the nanopolar region. We analyze three contributions of the EC effect: temperature-dependent dielectric dispersion, intrinsic pyroelectric effect and enhanced dielectric stiffness. The maximum EC coefficient is determined through the derivatives of the three components with respect to temperature. The proposed approach, in which the evolution of polarization correlation length is accounted for, cannot only provide a microscopic explanation for the thermally driven enhancement of EC responses, but also improves upon the existing models for estimating the EC effect in paraelectric phase of relaxors. Finally, some potential approaches for engineering the enhancement of EC coefficient are also suggested.
AB - The electrocaloric (EC) effect offers promise as a means to realize solid-state refrigeration, which requires EC materials possessing a pronounced pyroelectric effect over a broad temperature range. Pauli's master equation is adopted to investigate the recently observed phenomenon of enhanced EC effect above the Curie temperature in relaxor ferroelectrics. The proposed approach allows the EC coefficient to be determined within the framework of classic Landau-Ginzburg-Devonshire thermodynamics and the Maxwell relation, taking into account both the depolarization effect and dielectric permittivity dispersion based on the concept of superparaelectricity and the nanopolar region. We analyze three contributions of the EC effect: temperature-dependent dielectric dispersion, intrinsic pyroelectric effect and enhanced dielectric stiffness. The maximum EC coefficient is determined through the derivatives of the three components with respect to temperature. The proposed approach, in which the evolution of polarization correlation length is accounted for, cannot only provide a microscopic explanation for the thermally driven enhancement of EC responses, but also improves upon the existing models for estimating the EC effect in paraelectric phase of relaxors. Finally, some potential approaches for engineering the enhancement of EC coefficient are also suggested.
KW - Dielectric stiffness enhancement
KW - Electrocaloric effect
KW - Pauli's master equation
KW - Phenomenological theory
KW - Relaxor ferroelectrics
UR - http://www.scopus.com/inward/record.url?scp=79960385347&partnerID=8YFLogxK
U2 - 10.1016/j.actamat.2011.05.030
DO - 10.1016/j.actamat.2011.05.030
M3 - Article
AN - SCOPUS:79960385347
SN - 1359-6454
VL - 59
SP - 5574
EP - 5583
JO - Acta Materialia
JF - Acta Materialia
IS - 14
ER -