A low-temperature specific heat study of giant dielectric constant materials

Authors

C. P. Sun, National Sun Yat-Sen University, Taiwan
Jianjun Liu, Nebraska Center for Materials and Nanoscience, University of Nebraska-Lincoln,
J.-Y. Lin, National Chiao-Tung University, Taiwan
Chun-gang Duan, University of Nebraska-LincolnFollow
Wao-Ning Mei, University of Nebraska-LincolnFollow
H. D. Yang, National Sun Yat-Sen University, Taiwan

Date of this Version

2008

Comments

Published in Journal of Physics: Condensed Matter 20 (2008), 285214 (5pp); doi:10.1088/0953-8984/20/28/285214 1 Copyright © 2008 IOP Publishing Ltd. Used by permission. Online at http://stacks.iop.org/JPhysCM/20/285214

Abstract

A low-temperature specific heat study has been performed on the insulating giant dielectric constant material CaCu₃Ti₄O₁₂ and two related compounds, Bi_2/3Cu₃Ti₄O₁₂ and La_0.5Na_0.5Cu₃Ti₄O₁₂, from 0.6 to 10 K. From analyzing the specific heat data in a very low-temperature range, 0.6–1.5 K, and moderately low-temperature range, 1.5–5 K, in addition to the expected Debye terms, we observed significant contributions originating from the linear and Einstein terms, which we attributed as the manifestation of low-lying elementary excitations due to lattice vibrations occurring at the grain boundaries and induced by local defects. Together with the findings on electronic and mechanical properties, a phenomenological model is proposed to explain the high dielectric constant behavior in both low and high frequency regions.