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1.
M. Jochum H.-G. Unruh 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,5(2):163-168
Dielectric and Raman spectroscopic measurements have been performed to investigate the ferroelectric phase transition in . Single crystals were grown by the zone melting method. The frequency dependence of the dielectric permittivity from 1 MHz
to 1 GHz has been studied in a temperature range between 265 and 285 K. A Debye like dielectric dispersion was found, showing
a critical slowing down around K. Polarized Raman spectra have been taken between 220 and 310 K. Two softening modes have been found, one of A- and another one of B
/
B
g-symmetry. The phase transition mechanism in can be classified as partially order-disorder and partially displacive, confirming former structural results. It resembles
strongly that of monoclinic .
Received: 7 April 1998 / Revised: 5 June 1998 / Accepted: 16 June
1998 相似文献
2.
A. Bussmann-Holder A. R. Bishop 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,53(3):279-282
Motivated by recent experiments demonstrating suppression of
ferroelectricity with pressure in SrTi18O3, the dynamics of the
phase transition mechanism are reinvestigated within a nonlinear
polarizability model. For temperatures far above the phase transition polar
micro domains are formed which increase in size with decreasing temperature
to freeze out at Tc without forming long range order. Experimentally,
soft mode dynamics are simultaneously observed, evidencing that displacive
and order/disorder features coexist. In the ferroelectric phase both
components persist whereby an incomplete and inhomogeneous ferroelectric
state is formed. 相似文献
3.
V.A. Stephanovich 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,18(1):17-21
We predict the existence of a Griffiths phase in dielectrics with a concentrational crossover between dipole glass (electric
analog of spin glass) and ferroelectricity. Particular representatives of the above substances are KTaO3:Li, Nb, Na, or relaxor ferroelectrics like Pb1–xLaxZr0.65Ti0.35O3. Since this phase exists above the ferroelectric phase-transition temperature (but below that temperature for ordered substances),
we call it a “para-glass phase”. We assert that the difference between paraelectric and para-glass phases in the above substances
is the existence of clusters (inherent to the “ordinary” Griffiths phase of Ising magnets) of correlated dipoles. We show
that randomness plays a decisive role in the Griffiths (para-glass) phase formation: this phase does not exist in a mean field
approximation. To investigate the Griffiths phase properties, we calculate the density of Yang-Lee (YL) zeros in the partition
function and find that it has “tails” inherent to the Griffiths phase in the above temperature interval. We perform calculations
on the basis of our self-consistent equation for the long-range order parameter in an external electric field. This equation
has been derived in the framework of the random field theory. The latter automatically incorporates both short-range (due
to indirect interaction via transverse optical phonons of the host lattice) and long-range (ordinary dipole-dipole) interactions between impurity dipoles,
so that the problem of long-range interaction considerations does not appear in it.
Received 17 May 2000 相似文献
4.
F. Nad' P. Monceau J.M. Fabre 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,3(3):301-306
Conductivity and permittivity of the organic transfer salt (TMTTF)2Br have been measured at low frequencies (102-107 Hz) between room temperature down to 4 K. The real part of the permittivity, , is shown to grow below the temperature at which the conductivity is maximum due to charge localization of Mott-Hubbard type. reaches a maximum of 105-106 at 35 K-50 K depending on the samples. Decreasing temperature below , sharply decreases down to helium temperature through the antiferromagnetic phase transition at T N = 15 K. We explain the magnitude, the temperature and frequency dependence of as resulting from short range charge density wave states in the temperature range where charge localization occurs. This
interpretation is supported by recent X-ray scattering measurements.
Received: 10 October 1997 / Revised: 28 February 1998 / Accepted: 3 March 1998 相似文献
5.
Indrani Coondoo 《Solid State Communications》2007,142(10):561-565
Europium substituted samples of the compositions Sr1−xEuxBi2Ta2O9 (x=0.0,0.025,0.050,0.10 and 0.20) were synthesized by solid state reaction method and studied for their structural, dielectric and ferroelectric properties. The X-ray diffractograms confirmed the formation of single phase layered perovskite structure in all the samples. The temperature variation of dielectric constant shows that the Curie temperature (Tc) decreases on increasing concentration of europium. The dielectric loss reduces significantly with europium addition. The P-E studies of the Eu-substituted SBT ceramics show that the remanent polarization increases with increasing concentration of europium. 相似文献
6.
U. Schneider R. Brand P. Lunkenheimer A. Loidl 《The European physical journal. E, Soft matter》2000,1(1):67-73
The Nagel scaling and the modified scaling procedure proposed recently by Dendzik et al. have been applied to broadband dielectric data on two glass-forming liquids (glycerol and propylene carbonate) and three
plastic crystals (ortho-carborane, meta-carborane, and 1-cyano-adamantane). Our data extend the upper limit of the abscissa
range to considerably higher values than in previously published analyses. At the highest frequencies investigated, deviations
from a single master curve show up which are most pronounced in the Dendzik scaling plot. The loss curves of the plastic crystals
do not scale in the Nagel plot, but they fall onto a separate master curve in the Dendzik plot. In addition, we address the
question of a possible divergence of the static susceptibility near the Vogel-Fulcher temperature. For this purpose, the low-temperature
evolution of the high-frequency wing of the dielectric loss peaks is investigated in detail. No convincing proof for such
a divergence can be deduced from the present broadband data.
Received 14 June 1999 and Received in final form 4 October 1999 相似文献
7.
J. Osman D. R. Tilley R. Teh Y. Ishibashi M. N.A. Halif K.-H. Chew 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,52(1):143-150
In the presence of a surface the Landau-Devonshire equations of
ferroelectricity must be extended to include a boundary condition. For a
ferroelectric with a second-order transition in the case when the
polarization p(z) increases at the surface, it is well known that a
surface state occurs in a range of temperature above the bulk critical
temperature tCB . Here we explore the corresponding effect for a
first-order ferroelectric. We show that a surface state can occur, but only
if the surface effect is sufficiently strong. Analytic expressions are
derived and illustrated for p(z), the surface value pS =p(0) and the
free energy. The transition from the paraelectric state (p=0) to the
surface state is first order, and for completeness we establish the
dependence of the three critical temperatures (supercooling, thermodynamic
and superheating) on a boundary-condition parameter y. In a final section, we
derive and illustrate expressions for p(z)in the temperature range
t<tCB . 相似文献
8.
A. Naberezhnov S. Vakhrushev B. Dorner D. Strauch H. Moudden 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,11(1):13-20
Results of inelastic neutron scattering experiments between 300 K and 900 K on the relaxor ferroelectric PbMg
1/3
Nb
2/3
O3 are presented. Within a mode-coupling analysis the data are consistent with the observation of a strongly damped quasi-optic
excitation. It is demonstrated that below K a dynamical crossover takes place manifesting itself by a narrow central peak. This crossover is accompanied by the appearance
of strong damping of the transverse acoustic phonons, with the damping constant proportional to q4. Different physical models of the crossover are discussed.
Received 8 February 1999 相似文献
9.
Ch. Schwan F. Martin G. Jakob J.C. Martinez H. Adrian 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,14(3):477-481
We have investigated the crystal structure and the ferroelectric properties of BaTiO3 thin films with YBa2Cu3O as the bottom and Au as the top electrode. Epitaxial heterostructures of YBa2Cu3O and BaTiO3 were prepared by dc and rf sputtering, respectively. The crystal structure of the films was characterised by X-ray diffraction.
The ferroelectric behaviour of the BaTiO3 films was confirmed by hysteresis loop measurements using a Sawyer Tower circuit. We obtain a coercive field of 30 kV/cm
and a remanent polarisation of 1.25 μC/cm2. At sub-switching fields the capacitance of the films obeys a relation analogous to the Rayleigh law. This behaviour indicates
an interaction of domain walls with randomly distributed pinning centres. At a field of 5 MV/m we calculate a 3% contribution
of the irreversible domain wall motion to the total dielectric constant.
Received 24 June 1999 and Received in final form 27 August 1999 相似文献
10.
T. Dekola D. Isakov E. de Matos Gomes V. H. Nunes Rodrigues M. M.R. Costa 《The European Physical Journal B - Condensed Matter and Complex Systems》2009,68(4):519-522
Glycine glycinium perrhenate is a new hydrogen bonded crystalline material that exhibits several phase transitions at low
and high temperature. At room temperature the structure shows some special features. One dimensional polar chains, linked
by strong hydrogen bonds exist parallel to [100], [010] and [–110]. The structural, thermal and dielectric properties of this
new perrhenic salt are presented and a relationship is established. 相似文献
11.
R. Enjalbert J. Galy Y. Vysochanskii A. Ouédraogo P. Saint-Grégoire 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,8(2):169-177
The structural change occurring in between the paraelectric and the ferroelectric phases is investigated by means of X-ray diffraction. Details of the structure
in both phases are obtained and the role of the lone pair is discussed in the light of structural data. In agreement with the 2/
m to m symmetry lowering, polar displacements are found within the m plane away from a particular crystallographic direction but antiparallel displacements occur also. These results are discussed
in the frame of the phenomenological theory which predicts a particular temperature dependence of the dielectric polarization
in this crystal.
Received: 10 July 1998 相似文献
12.
P. N. Timonin 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,64(1):125-138
Phenomenological thermodynamic theory describing the properties of metastable states in disordered ferromagnets and ferroelectrics
with frustrative random interactions is developed and its ability to describe various nonergodic phenomena in real crystals
is demonstrated. 相似文献
13.
A. K. Bandyopadhyay P. C. Ray V. Gopalan 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,65(4):525-531
Ferroelectric materials, such as lithium niobate, show interesting non-linear hysteresis behavior that can be explained by
a dynamical system analysis. By using variational principle, a non-linear Klein-Gordon (K-G) equation is derived for lithium
niobate type of uniaxial ferroelectrics involving various types of energy, which was not considered previously to construct
the Hamiltonian. This leads to soliton solutions under different conditions of soliton velocity. The critical value of the
(dimensional) effective electric field has been estimated to be 54–58 kV/cm for lithium niobate depending on the impurity
content in these type inhomogeneous ferroelectrics. Beyond this critical field, there is no existence of solitons. This critical
field is related to a break-up mechanism of Landau-Ginzburg two-well potential to a single well, as the driving force is increased. 相似文献
14.
S. Moreno R.G. Rubio G. Luengo F. Ortega M.G. Prolongo 《The European physical journal. E, Soft matter》2001,4(2):173-182
The complex dielectric permittivity has been measured for three poly(ethylenglycol)-b-poly(propylenglycol)-b-poly(ethylenglycol)
copolymers with different content of poly(ethylenglycol) (15%, 33% and 80%), and increasing degree of crystallinity (0%, 10%
and 20%, respectively). Only the non-crystalline sample shows the normal mode relaxation together with the segmental (α-relaxation)
and the Johari-Goldstein (β-relaxation) modes. The crystalline samples show also polarization contributions due to the existence
of interfaces between the crystallites and the amorphous phase. The relaxation times of the (α and normal modes can be described
by a VFT equation with the same value of T0. There is a slowing-down of the segmental mode due to the presence of crystallites. The temperature dependence of the α and
β relaxations in the copolymers is very similar to that found in pure PPG, while there are significant differences in the
case of the normal mode of the non-crystalline sample. The size of the cooperatively rearranging regions CRR, and the width
of the glass transition region increase slightly with the degree of crystallinity. The temperature dependence of the size
of CRRs is compatible with the prediction of fluctuation theory. No systematic effect of the degree of crystallinity on the
β-relaxation has been found. Near T
g the β-relaxation time is close to the primitive time of the coupling model.
Received: 31 May 2000 相似文献
15.
M. Pinterić T. Vuletić M. Lončarić S. Tomić J.U. von Schütz 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,16(3):487-493
We report a detailed characterization of an unique 3-fold commensurate insulating state in single crystals of the organic
– inorganic d hybrid Cu(DMe-DCNQI)2 systems with deuterated and partially deuterated DCNQI ring, by means of low-frequency dielectric spectroscopy. A broad relaxation
mode of strength centred at kHz is observed in the hysteresis temperature region in which the insulating phase coexists with metallic islands. At lower
temperatures, outside the nucleation range, the relaxation narrows, approaching a Debye-like form for an overdamped response
of a system with a single degree of freedom. Both, the relaxation strength and the mean relaxation time () are much larger than that expected for single-particle excitations. These features suggest the origin of the dielectric
relaxation as an intrinsic property of the N = 3 charge density wave state.
Received 1 December 1999 and Received in final form 5 April 2000 相似文献
16.
X. G. Tang Q. X. Liu J. Wang H. L. W. Chan 《Applied Physics A: Materials Science & Processing》2009,96(4):945-952
The effect of a dc bias field on the diffuse phase transition and nonlinear dielectric properties of sol-gel derived Ba(Zr0.2Ti0.8)O3 (BZT) ceramics are investigated. Diffuse phase transitions were observed in BZT ceramics and the Curie–Weiss exponent (CWE)
was γ∼2.0. The dielectric constant versus temperature characteristics and the γ in the modified Curie–Weiss law, ε
−1=ε
m
−1[1+(T−T
m
)
γ
/C1](1≤γ≤2), as a function of the dc bias field was obtained for BZT ceramics. The results indicated that γ is a function of dc bias field, and the γ value decreased from 2.04 to 1.73 with dc bias field increasing from 0 to 20 kV/cm. The dielectric constant decreases with
increasing dc bias field, indicating a field-induced phase transition. The dc bias field has a strong effect on the position
of the dielectric peak and affects the magnitude of the dielectric properties over a rather wide temperature range. The peak
temperature of the dielectric loss does not coincide with the dielectric peak and an obvious minimum value for the dielectric
loss at the temperature of the dielectric peaks is observed. At room temperature, 300 K, the high tunability (K=80%), the low loss tangent (≈0.01) and the large FOM (74), clearly imply that these ceramics are promising materials for tunable capacitor-device applications. 相似文献
17.
E. Buixaderas V. Porokhonskyy A. Paskhin M. Savinov J. Petzelt 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,30(3):319-329
Barium sodium niobate (BNN) single crystals are studied by IR spectroscopy, time-domain THz transmission spectroscopy, HF
coaxial wave-guide technique and LF dielectric spectroscopy to cover the frequency range 102-1014 Hz in a wide temperature interval. The dielectric response parallel and perpendicular to the polar c-axis is discussed. The ferroelectric transition at T
c
= 830 K is driven by a relaxational soft mode coupled with another central-mode type relaxation which both gradually disappear
on cooling in the ferroelectric phase. Below T
i
the parameters of the expected IR active amplitudon were estimated. The low-temperature permittivity increase on cooling
for the
field direction has been explained by an incipient proper ferroelectric-ferroelastic transition driven by an IR and Raman
active B2-symmetry soft mode.
Received 24 August 2002 Published online 19 December 2002
RID="a"
ID="a"e-mail: buixader@fzu.cz 相似文献
18.
R. Richert 《The European Physical Journal B - Condensed Matter and Complex Systems》2009,68(2):197-200
In a variety of samples, conductivity is a limiting factor regarding the resolution of dielectric loss peaks of interest.
One approach to eliminating the signal that originates from conductivity is the use of insulating layers on one or both electrodes.
For the typical case, it is shown that insulation layers add errors rather than improving the situation. 相似文献
19.
J. Dec W. Kleemann Th. Woike R. Pankrath 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,14(4):627-632
The complex dielectric susceptibility of Sr
0.61
Ba
0.39
Nb
2
O
6
:Ce
3+
(SBN61:Ce) has been measured at frequencies and temperatures before and after poling. The relaxor behaviour with large polydispersivity observed above the ferroelectric phase transition
temperature, T
c
= 360 and 340 K for x
(Ce) = 0 and 0.0066, respectively, is perfectly modeled within the framework of Chamberlin's dynamically correlated domain approach.
Below T
c
the dynamic nanodomain state crosses over into a ferroelectric state with polydispersive domain wall dynamics at very low
frequencies. Presumably SBN61:Ce belongs to the three-dimensional random field Ising rather than to the dipole glass universality
class.
Received 1 October 1999 相似文献