147 research outputs found
Anelastic relaxor behavior of Pb(Mg1/3Nb2/3)O3
Elastic storage modulus and loss of relaxor lead magnesium niobate ceramics,
Pb(Mg1/3Nb2/3)O3, have been measured with dynamic mechanical analyzer in single
cantilever mode in the temperature range from 170 K to 320 K and at frequencies
from 0.1 Hz to 50 Hz. The dependence of the elastic susceptibility (inverse
modulus) on temperature and frequency of the driving force has characteristics
of typical relaxor behavior that can be well described with the Vogel-Fulcher
law. The parameters of the Vogel-Fulcher relation exhibit similar values for
the dielectric and anelastic relaxations. Similarities and differences between
anelastic and dielectric relaxor behaviors are identified.Comment: accepted in Applied Physics Letter
Nonlinear dynamics of polar regions in paraelectric phase of (Ba1-x,Srx)TiO3 ceramics
The dynamic dielectric nonlinearity of barium strontium titanate
(Ba1-x,Srx)TiO3 ceramics is investigated in their paraelectric phase. With the
goal to contribute to the identification of the mechanisms that govern the
dielectric nonlinearity in this family, we analyze the amplitude and the phase
angles of the first and the third harmonics of polarization. Our study shows
that an interpretation of the field-dependent polarization in paraelectric
(Ba1-x,Srx)TiO3 ceramics in terms of the Rayleigh-type dynamics is inadequate
for our samples and that their nonlinear response rather resembles that
observed in canonical relaxor Pb(Mg1/3Nb2/3)O3.Comment: published in: Sina Hashemizadeh and Dragan Damjanovic, Applied
Physics Letters 110 (19), 192905 (2017
A morphotropic phase boundary system based on polarization rotation and polarization extension
Many ferroelectric solid solutions exhibit enhanced electromechanical properties at the morphotropic boundary separating two phases with different orientations of polarization. The mechanism of properties enhancement is associated with easy paths for polarization rotation in anisotropically flattened free energy profile. Another mechanism of properties enhancement related to free energy flattening is polarization extension. It is best known at temperature-driven ferroelectric-paraelectric phase transitions and may lead to exceedingly large properties. Its disadvantage is temperature instability of the enhancement. In this paper a temperature-composition phase diagram is proposed that exhibits compositionally driven-phase transitions with easy paths for both polarization rotation and polarization extension
Separation of piezoelectric grain resonance and domain wall dispersion in PZT ceramics
We report on the experimental investigation of a high-frequency
(1MHz - 1.8GHz) dielectric dispersion in unpoled and poled
Pb(Zr,Ti)O3 ceramics. Two overlapping loss peaks could be revealed in the
dielectric spectrum. The linear dependence between the lower-frequency peak
position and average grain size D, which holds for D< 10mkm, indicates that the
corresponding polarization mechanism originates from piezoelectric resonances
of grains. The intensity of the higher-frequency peak is drastically reduced by
poling. It is thus proposed that this loss peak is related to domain-wall
contribution to the dielectric dispersion.Comment: 8 pages, 3 figure
Elastic, dielectric and piezoelectric anomalies and Raman spectroscopy of 0.5Ba(Ti0.8Zr0.2)O3-0.5(Ba0.7Ca0.3)TiO3
The solid solution 0.5Ba(Ti0.8Zr0.2)O3-0.5(Ba0.7Ca0.3)TiO3 (BCZT) is a
promising lead-free piezoelectric material with exceptionally high
piezoelectric coefficients. The strong response is related to structural
instabilities close to ambient temperature. We report here on
temperature-induced anomalies in the dielectric, piezoelectric, and elastic
coefficients and Raman spectroscopy of ceramic BCZT. The data indicate
ferroelectric-ferroelectric structural phase transitions in this material in
addition to those previously reported. An anomaly is also observed above the
Curie temperature TC and is associated with the loss of polar structure that
persists thirty degrees above TC
Rotator and extender ferroelectrics: Importance of the shear coefficient to the piezoelectric properties of domain-engineered crystals and ceramics
The importance of a high shear coefficient d15 (or d24) to the piezoelectric
properties of domain-engineered and polycrystalline ferroelectrics is
discussed. The extent of polarization rotation, as a mechanism of piezoelectric
response, is directly correlated to the shear coefficient. The terms "rotator"
and "extender" are introduced to distinguish the contrasting behaviors of
crystals such as 4mm BaTiO3 and PbTiO3. In "rotator" ferroelectrics, where d15
is high relative to the longitudinal coefficient d33, polarization rotation is
the dominant mechanism of piezoelectric response; the maximum longitudinal
piezoelectric response is found away from the polar axis. In "extender"
ferroelectrics, d15 is low and the collinear effect dominates; the maximum
piezoelectric response is found along the polar axis. A variety of 3m, mm2 and
4mm ferroelectrics, with various crystal structures based on oxygen octahedra,
are classified in this way. It is shown that the largest piezoelectric
anisotropies d15/d33 are always found in 3m crystals; this is a result of the
intrinsic electrostrictive anisotropy of the constituent oxygen octahedra.
Finally, for a given symmetry, the piezoelectric anisotropy increases close to
ferroelectric-ferroelectric phase transitions; this includes morphotropic phase
boundaries and temperature induced polymorphic transitions.Comment: accepted in J. Appl. Phy
Piezoelectric nonlinearity and frequency dispersion of the direct piezoelectric response of BiFeO3 ceramics
We report on the frequency and stress dependence of the direct piezoelectric
d33 coefficient in BiFeO3 ceramics. The measurements reveal considerable
piezoelectric nonlinearity, i.e., dependence of d33 on the amplitude of the
dynamic stress. The nonlinear response suggests a large irreversible
contribution of non-180{\deg} domain walls to the piezoelectric response of the
ferrite, which, at present measurement conditions, reached a maximum of 38% of
the total measured d33. In agreement with this interpretation, both types of
non-180{\deg} domain walls, characteristic for the rhombohedral BiFeO3, i.e.,
71{\deg} and 109{\deg}, were identified in the poled ceramics using
transmission electron microscopy (TEM). In support to the link between
nonlinearity and non-180{\deg} domain wall contribution, we found a correlation
between nonlinearity and processes leading to deppining of domain walls from
defects, such as quenching from above the Curie temperature and
high-temperature sintering. In addition, the nonlinear piezoelectric response
of BiFeO3 showed a frequency dependence that is qualitatively different from
that measured in other nonlinear ferroelectric ceramics, such as "soft"
(donor-doped) Pb(Zr,Ti)O3 (PZT); possible origins of this dispersion are
discussed. Finally, we show that, once released from pinning centers, the
domain walls can contribute extensively to the electromechanical response of
BiFeO3; in fact, the extrinsic domain-wall contribution is relatively as large
as in Pb-based ferroelectric ceramics with morphotropic phase boundary (MPB)
composition, such as PZT. This finding might be important in the search of new
lead-free MPB compositions based on BiFeO3 as it suggests that such
compositions might also exhibit large extrinsic domain-wall contribution to the
piezoelectric response.Comment: 38 pages, 11 figure
Antiferroelectric–ferroelectric phase boundary enhances polarization extension in rhombohedral Pb(Zr,Ti)O3
The main mechanism of properties enhancement in the morphotropic phase boundary region separating tetragonal and rhombohedral phases of Pb(Zr1-xTix)O-3 (PZT) is related to polarization rotation. It is shown here that in proximity of the morphotropic phase boundary separating antiferroelectric and rhombohedral phases (near x = 0.1) and at elevated temperatures the properties are dominated by polarization extension. These results may provide a guideline for developing alternative piezoelectric materials to PZT. (C) 2011 American Institute of Physics. [doi:10.1063/1.3666233
- …