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ISSN : 1225-0562(Print)
ISSN : 2287-7258(Online)
Korean Journal of Materials Research Vol.22 No.7 pp.342-345

Dielectric Properties and Phase Transformation of Poled<001>-Oriented Pb(Mg1/3Nb2/3)O3-PbTiO3 Single Crystals

Lee, Eun-Gu, Lee, Jae-Gab


The dielectric properties and phase transformation of poled <001>-oriented Pb(Mg1/3Nb2/3)O3-x%PbTiO3(PMN-x%PT) single crystals with compositions of x=20, 30, and 35mole% are investigated for orientations both parallel andperpendicular to the [001] poling direction. An electric-field-induced monoclinic phase was observed for the initial poled PMN-30PT and PMN-35PT samples by means of high-resolution synchrotron x-ray diffraction. The monoclinic phase appears from−25oC to 100oC and from −25oC to 80oC for the PMN-30PT and PMN-35PT samples, respectively. The dielectric constant (ε)-temperature (T) characteristics above the Curie temperature were found to be described by the equation(1/ε−1/εm)1/n=(T−Tm)/C, where εm is the maximum dielectric constant and Tm is the temperature giving εm, and n and C are constants that changewith the composition. The value of n was found to be 1.82 and 1.38 for 20PT and 35PT, respectively. The results of meshscans and the temperature-dependence of the dielectric constant demonstrate that the initial monoclinic phase changes to a singledomain tetragonal phase and a to paraelectric cubic phase. In the ferroelectric tetragonal phase with a single domain state, thedielectric constant measured perpendicular to the poling direction was dramatically higher than that measured in the paralleldirection. A large dielectric constant implies easier polarization rotation away from the polar axis. This enhancement is believedto be related to dielectric softening close to the morphotropic phase boundary.

분극된<001> 방위 Pb(Mg1/3Nb2/3)O3-PbTiO3 단결정의 유전 특성 및 상전이

이은구, 이재갑