86 research outputs found
High Dielectric Permittivity in AFeBO Nonferroelectric Perovskite Ceramics (A - Ba, Sr, Ca; B - Nb, Ta, Sb)
AFeBO(A- Ba, Sr, Ca; B-Nb, Ta, Sb) ceramics were
synthesized and temperature dependencies of the dielectric permittivity were
measured at different frequencies. The experimental data obtained show very
high values of the dielectric permittivity in a wide temperature interval that
is inherent to so-called high-k materials. The analyses of these data establish
a Maxwell-Wagner mechanism as a main source for the phenomenon observed.Comment: 6 pages, 7 figure
New, Lead Free, Perovskites With a Diffuse Phase Transition: NaNbO_{3} ~ Solid Solutions
Some of (1-x)NaNbO_3-(x)ABO_3 perovskite solid solutions exhibit a dramatic
diffusion of the dielectric permittivity epsilon' maximum and relaxor-type
behavior when the second component concentration exceeds a threshold value x_0.
The concentration phase transition to the relaxor-like phase is abrupt (of the
first order kind) that is seen from the step in the dependence of the
epsilon'(T) maximum temperature, T_m, on x. The precursor of this transition is
a giant (up to 100 K) temperature hysteresis of epsilon'(T). Some relaxor-like
properties appear even at x < x_0 in the course of cooling while disappear in
the course of heating. The experimental data obtained are qualitatively
described within a Landau-type phenomenological approach, assuming the
relaxor-type behavior to be local stress-induced.Comment: 5 figure
Diffusive phase transitions in ferroelectrics and antiferroelectrics
In this paper, we present a microscopic model for heterogeneous ferroelectric
and an order parameter for relaxor phase. We write a Landau theory based on
this model and its application to ferroelectric PbFeTaO
(PFT) and antiferroelectric NaNbO:Gd. We later discuss the coupling between
soft mode and domain walls, soft mode and quasi-local vibration and resulting
susceptibility function.Comment: 6 pages, Fundamental physics of ferroelectrics 200
Condensation of the atomic relaxation vibrations in lead-magnesium-niobate at
We present neutron diffraction, dielectric permittivity and photoconductivity
measurements, evidencing that lead-magnesium niobate experiences a diffuse
phase transformation between the spherical glass and quadrupole glass phases,
in the temperature interval between 400 K and 500 K, with the quadrupole phase
possessing extremely high magnitudes of dielectric permittivity. Our analysis
shows that the integral diffuse scattering intensity may serve as an order
parameter for this transformation. Our experimental dielectric permittivity
data support this choice. These data are important for the aplications desiring
giant dielectric responses, in a wide temperature intervals and not related to
electron's excitations.Comment: 6 figure
Nontrivial dependence of dielectric stiffness and SHG on dc bias in relaxors and dipole glasses
Dielectric permittivity and Second Harmonic Generation (SHG) studies in the
field-cooled mode show a linear dependence of dielectric stiffness (inverse
dielectric permittivity) on dc bias in PMN-PT crystals and SHG intensity in
KTaO:Li at small Li concentrations. We explain this unusual result in the
framework of a theory of transverse, hydrodynamic-type, instability of local
polarization.Comment: 5 figure
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