Formation mechanism and relaxor ferroelectric properties of lead lithium iron tungstate ceramics
Journal
Journal of Materials Research
Journal Volume
10
Journal Issue
11
Pages
2755-2763
Date Issued
1995
Author(s)
Hwang W.-S.
Abstract
The formation mechanism and ferroelectric properties of Pb(Li 1/4 Fe 1/4 W 1/2 )O 3 prepared by solid-state reaction have been investigated in this study. The formation processes of Pb(Li 1/4 Fe 1/4 W 1/2 )O 3 are characterized to be an initial reaction of lead tungstates PbWC 4 and Pb 2 WO 5 at a low temperature range, followed by a subsequent reaction to produce Pb(Li 1/4 Fe 1/4 W 1/2 )O 3 from above 650 ¢XC. Through a two-stage calcination (700 ¢XC/quenching-regrinding-710 ¢XC/8 h), a nearly single phase of Pb(Li 1/4 Fe 1/4 W 1/2 )O 3 is obtained. This compound exhibits a cubic perovskite structure (£\ = 8.0113 ?) with a partial ordering arrangement of B-site cations. Above 720 ¢XC, Pb(Li 1/4 Fe 1/4 W 1/2 )O 3 becomes thermodynamically unstable and gradually decomposes in forming elongated Pb 2 WO 5 grains, thereby resulting in a nonhomogeneous microstructure. As the ac frequency increases, the maximum dielectric permittivity of Pb(Li 1/4 Fe 1/4 W 1/2 )O 3 significantly decreases; in addition, the corresponding temperature increases. The strong frequency dependence of dielectric properties, as well as the critical exponent and diffuseness evaluated through a modified permittivity-temperature equation proposed in this study, verify the relaxor characteristics of Pb(Li 1/4 Fe 1/4 W 1/2 )O 3 . ? 1995, Materials Research Society. All rights reserved.
Type
journal article