共查询到20条相似文献,搜索用时 14 毫秒
1.
A. Chaipanich G. Rujijanagul T. Tunkasiri 《Applied Physics A: Materials Science & Processing》2009,94(2):329-337
Lead zirconate titanate (PZT) ceramic-cement-based composites have increasingly been recognized as an attractive new composite
material for use as a sensor in structural applications. In this work, PZT was doped with Sr and Sb (PSZT) to give it greater
dielectric constant (ε
r) and higher piezoelectric coefficient (d
33) values than normal PZT and is the first time that it is mixed with normal Portland cement to produce a 0–3 connectivity
PSZT–Portland cement composite using PSZT contents of 50% and 70% by volume. Scanning electron micrographs show PSZT ceramic
particles closely surrounded by the hydrated cement matrix where a dense microstructure can be observed in the interfacial
zone. Both the ε
r and d
33 values were found to increase with PSZT content and the values are amongst the highest so far for these types of composites,
where the ε
r and d
33 values reached 590 and 48 pC/N, respectively. 相似文献
2.
Composite ferroic BaTiO3–Ni films with different Ni content were fabricated by radio frequency (RF) cosputtering method. Complex impedance analysis
indicates that the addition of Ni has greatly reduced the resistivity of the Ni-enriched boundaries. All the composite films
exhibit room temperature ferromagnetism, while the ferroelectricity of the films is degrading with increasing Ni content.
Dielectric measurements reveal that below the Ni content of 22.7 at.%, the dielectric response follows the general percolation
theory and the increase of dielectric constant and loss tangent with Ni addition is mainly associated with the microstructure
induced nanocapacitor effect and Maxwell–Wagner interface polarization which also induces significant dielectric anomaly at
low frequency range. 相似文献
3.
M. Kosmowska K. Orzechowski 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,62(4):411-416
A critical anomaly of electric permittivity in the vicinity of the consolute
critical point of an ethanol and dodecane mixture has been measured and
analyzed. A method of analysing the permittivity anomaly, which enhances the
credibility of the fitting, has been proposed. We have found out that the
exponent predicted in theoretical expectations, 1-α = 0.89,
describes the anomaly correctly. However, in spite of the application of the
improved method, it is not possible to obtain the value of the fitted
critical exponent with satisfying precision. 相似文献
4.
M. Abarkan M. Aillerie J. P. Salvestrini M. D. Fontana E. P. Kokanyan 《Applied physics. B, Lasers and optics》2008,92(4):603-608
We report the optical and dielectric properties in hafnium (Hf)-doped lithium niobate (LN) crystals. We investigated samples
of congruent composition with various doping concentration varying from 0 to 8 mol%. The clamped and unclamped values of the
electro-optic coefficient r
22 of Hf-doped LN and the corresponding dielectric permittivity as well, have been experimentally determined and compared with
the results obtained in undoped congruent LN crystals. We show that the electro-optic and dielectric properties are only slightly
affected by the introduction of hafnium ions, and therefore Hf-doped LN has the advantage of low photorefractive damage compared
with the undoped congruent LN. 相似文献
5.
Y. J. Wu Y. Q. Lin S. P. Gu X. M. Chen 《Applied Physics A: Materials Science & Processing》2009,97(1):191-194
La0.5Bi0.5MnO3 ceramics with a single phase were prepared by a solid-state reaction method, and their dielectric properties were characterized.
Two dielectric relaxations with a giant dielectric constant were identified in the temperature range from 125 to 350 K. The
electron hopping between Mn3+ and Mn4+ was found to be the origin of the dielectric relaxation at low temperatures (125–200 K) with an activation energy of 0.18 eV.
The high temperature (200–350 K) dielectric relaxation can be attributed to the conduction. 相似文献
6.
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
7.
S. Firmino?Mendes C. M. Costa V. Sencadas J. Serrado?Nunes P. Costa R. Gregorio J. L. Gomez Ribelles S. Lanceros-Méndez 《Applied Physics A: Materials Science & Processing》2009,96(4):1037-908
In this work, poly(vinilidene fluoride)/Pb(Zr0.53Ti0.47)O3([PVDF]1−x
/[PZT]
x
) composites of volumetric fractions x and (0–3) type connectivity were prepared in the form of thin films. PZT powder of crystallite size of 0.84, 1.68, and 2.35
μm in different amounts of PZT (10, 20, 30, and 40%) was mixed with the polymeric matrix. The crystalline phase of the polymeric
matrix was the nonpolar α-phase and the polar β-phase.
Dielectric and dynamic mechanical (DMA) measurements were performed to these composites in order to evaluate the influence
of particle size and the amount of PZT filler with respect to the PVDF matrix. The inclusion of ceramic particles in the PVDF
polymer matrix increases the complex dielectric constant and dynamical mechanical response of the composites. A similar behavior
is observed for the α- or β-phase of the polymeric matrix indicating that the PVDF polymer matrix is not particularly relevant for the composite behavior.
On the other hand, ceramic size and especially content play the major role in the increase of the dielectric response and
the room temperature storage modulus. In particular, the storage modulus increases with increasing PZT concentration, but
this increase is more pronounced, in terms of maximum value, for the sample with 2.35 μm particle size; DMA reveals two main
relaxations in the analyzed samples. A low-temperature process maximum at ca. −40°C, usually labeled by β or α
a
associated to the T
g
of the polymer and the α-relaxation at temperatures above 30°C. The β-relaxation is also observed in the dielectric measurements.
The models used to asses the dielectric behavior of the samples with increasing PZT concentration indicate that the particle–matrix
interaction plays a relevant role, as well as the particle asymmetry and relative orientation, being the Yamada model the
most appropriate to describe the composite behavior.
An erratum to this article can be found at 相似文献
8.
Microstructures and impedance characteristics of chemical-solution-derived Bi3.15Nd0.85Ti3O12 thin films were studied as functions of temperature. A dielectric anomaly was found at around 450°C, corresponding to the
paraelectric to ferroelectric transition. Via complex impedance studies, grain and grain boundary contributions to the impedance
were separated. The resistance of grain and grain boundaries is found governed by the same kind of space charge with an activation
energy around 1.1 eV, close to that of oxygen vacancies in perovskite ferroelectrics. The low temperature ac conductance of
BNdT thin films shows a frequency dispersion, which can also be ascribed to space charges mainly due to oxygen vacancies.
The results were compared with SrBi2Ta2O9 in terms of oxygen vacancy conductivity. 相似文献
9.
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
10.
S. K. Patri R. N. P. Choudhary 《Applied Physics A: Materials Science & Processing》2009,94(2):321-327
Bismuth layered perovskite structures show interesting physical properties varying as a function of external parameters (temperature,
frequency, electric and magnetic fields). When a magnetic ion is incorporated in some of these materials, some of the structures
show simultaneous ferroelectricity and ferro/antiferromagnetism. Thus, they exhibit magnetoelectric properties under the influence
of an external magnetic field. This paper compares the structural (XRD and SEM) and electrical properties of two eight-layered
Aurivillius oxides. 相似文献
11.
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
12.
Yew Von Lim Haiming Fan Zexiang Shen Chiang Huen Kang Yuanping Feng Shijie Wang 《Applied Physics A: Materials Science & Processing》2009,95(2):555-562
The silica supported titania nanocomposite thin films with controllable particle size and phase content were successfully
prepared by a convenient post annealing approach involving in solid-solid interfacial reaction. The effects of growth conditions,
such as the annealing temperature and silicon concentration on the particle size and phase content, were systematically studied
by using Atomic force microscopy (AFM), Raman spectroscopy, X-ray diffraction (XRD), and X-ray spectroscopy (XPS). The results
indicate that the silicon concentration is a dominant factor in the morphology, crystallization and phase transformation of
these nanocomposites. A mechanism for the high temperature phase transformation is also proposed based on the migration of
the oxygen vacancies. 相似文献
13.
L. Lejček 《Czechoslovak Journal of Physics》2004,54(9):965-973
The creation and the coalescence of inclusions has recently been observed in smectic C* freely suspended films at the temperature
near the smectic C*-cholesteric phase transition. A small finite anchoring energy permits to describe small inclusions by
analytical approximate solutions of dipolar or quadrupolar type. Using the proposed solutions our model enables us to discuss
the coalescence of smallest inclusions and their observed growth.
This work was supported by the research project AV0Z1-010-914 and by Grant No. 202/02/0840 of the Grant Agency of the Czech
Republic. 相似文献
14.
H. Y. Zhang Y. P. Zhang W. H. Liu Y. Q. Wang J. G. Yang 《Applied physics. B, Lasers and optics》2009,96(1):67-70
We show theoretically that the frequency range of the zero-averaged refractive-index gap can be substantially extended in
a photonic heterostructure containing negative-index materials. This photonic heterostructure consists of different one-dimensional
(1D) photonic crystals. The constituent 1D photonic crystals have to be properly chosen in such a way that their zero-averaged
refractive-index gap of the adjacent photonic crystals overlap each other. 相似文献
15.
K.?Sudheendran M.?Ghanashyam?Krishna K.?C.?James?Raju 《Applied Physics A: Materials Science & Processing》2009,95(2):485-492
Bismuth Zinc niobate (Bi1.5Zn1.0Nb1.5O7) thin films were deposited by pulsed laser deposition (PLD) method on fused silica substrates at different oxygen pressures.
The structural, microwave dielectric and optical properties of these thin films were systematically studied for both the as-deposited
and the annealed films at 600°C. The as-deposited films were all amorphous in nature but crystallized on annealing at 600°C
in air. The surface morphology as studied by atomic force microscopy (AFM) reveals ultra-fine grains in the case of as-deposited
thin films and cluster grain morphology on annealing. The as-deposited films exhibit refractive index in the range of 2.36–2.53
(at a wavelength of 750 nm) with an optical absorption edge value of 3.30–3.52 eV and a maximum dielectric constant of 11
at 12.15 GHz. On annealing the films at 600°C they crystallize to the cubic pyrochlore structure accompanied by an increase
in band gap, refractive index and microwave dielectric constant. 相似文献
16.
17.
P. Cluzeau F. Bougrioua G. Joly L. Lejček H. T. Nguyen 《Czechoslovak Journal of Physics》2004,54(3):365-376
A simplified model of an inclusion represented by (+1)-wedge disclination and an accompanying hyperbolic defect ((−1)-wedge
disclination) in smectic C* free standing films is used to describe the early stage of the ordering process of inclusions
into chains. The elastic interaction between inclusions and their associated hyperbolic defects is used to discuss the dynamics
observed experimentally during the inclusion chaining when inclusions are at distances much larger than their radii.
This work was also supported by Grant No. 202/02/0840 of the Grant Agency of the Czech Republic and by the research project
AV0Z1-010-914. 相似文献
18.
T. Bonaedy Y. S. Koo K. D. Sung K. M. Song N. Hur J. H. Jung 《Applied Physics A: Materials Science & Processing》2008,93(2):517-520
We have investigated the role of the grain boundary on the resistive magnetodielectric property of polycrystalline γ-Fe2O3 through impedance spectroscopy measurements. Depending on the sample preparation temperature, the dielectric constant of
γ-Fe2O3 is significantly different especially at low frequencies (<104 Hz) and high temperatures (>200 K). The value of the magnetodielectric effect at a specific frequency and the resonance frequency
for the maximized magnetodielectric effect are different, although polycrystalline γ-Fe2O3 samples show a quite similar magnetoresistance. Through the experimentally obtained resistance ratio between the grain and
the grain boundary, we can reproduce the magnetodielectric curves based on the Maxwell–Wagner model and the measured magnetoresistance. 相似文献
19.
I.?A.?Santos R.?G.?Mendes J.?A.?Eiras J.?de?Los?S.?Guerra E.?B.?Araújo 《Applied Physics A: Materials Science & Processing》2009,95(3):757-760
The dielectric properties of Sr0.75Ba0.25Nb2O6 relaxor ferroelectric thin films were carefully analyzed. In contrast to bulk samples which present three distinct dielectric
relaxation phenomena Sr0.75Ba0.25Nb2O6 thin films present only two of them. The suppression of the third anomaly can be mainly attributed to the narrow grain size
distribution of nanograins and weak tensile strains imposed to the film from the substrate. The whole set of results point
to the interpretation of a dielectric response characteristic of mesoscopic structure, which is composed of clusters and nanodomains. 相似文献
20.