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1.
Ba0·5Sr0·5Ti0·6Zr0·4O3 ceramic has been prepared through solid state reaction route. X-ray diffraction shows that the sample has cubic perovskite
structure with space group Pm-3m at room temperature. Temperature dependent dielectric study of the ceramic has been investigated in the frequency range 50
Hz-1 MHz. The density of the sample is determined using Archimedes’ principle and is found to be ∼99% of X-ray density. The
dielectric study revealed diffuse phase transition of second order. A broad dielectric anomaly coupled with the shift of dielectric
maxima toward a higher temperature with increasing frequency indicates the relaxor-type behaviour in the ceramics. The index
of relaxation (γ) and the broadening parameter (Δ) were estimated from a linear fit of the modified Curie-Weiss law. The value of γ ∼ 1·72 indicates the strong relaxor nature of the ceramic. A remarkably good fit to the Vogel-Fulcher relation further supports
such a relaxor nature. 相似文献
2.
Qiang Zhang Zhenrong Li Lihua Li Zhuo Xu Xi Yao 《Journal of Materials Science: Materials in Electronics》2011,22(9):1490-1494
(1−x)(0.36BiScO3–0.64PbTiO3)–xLiNbO3 (BSPT64–xLN) high-temperature relaxor ferroelectric ceramics near the morphotropic phase boundary (MPB) composition were investigated.
X-ray diffraction showed a change in symmetry from MPB phase to rhombohedral phase with LiNbO3 content increasing. A change from normal ferroelectric features to relaxor ferroelectric features was observed with LiNbO3 substitution up to x = 0.06, while high-temperature dielectric relaxation was exhibited at T
max ~230 to 383°C for 0.02 ≤ x ≤ 0.06. The BSPT64–xLN ceramics with x = 0.02 LiNbO3 exhibited good piezoelectric properties compared with BS–0.64PT ceramics: piezoelectric coefficients d
33 = 505pC/N, planar electromechanical coupling factors k
p = 0.47, and remnant polarization P
r = 40 μC/cm2, respectively. The annealing temperature dependence of piezoelectric response for BSPT64–xLN ceramics was measured and it was found that the piezoelectric properties decreased slightly before 210°C for x = 0.02 and 0.04, showing excellent thermal stability, which indicated that BSPT64–xLN relaxor ferroelectric ceramics can be used in the range of high temperature compared to Pb-based relaxor ferroelectrics. 相似文献
3.
A new member of lead-free piezoelectric ceramics of the BNT-based group, (1 − x)Bi0·5Na0·5TiO3−x
BaNb2O6, was prepared by conventional solid state reaction and its dielectric properties and relaxation was investigated. X-ray diffraction
showed that BaNb2O6 diffused into the lattice of Bi0·5Na0·5TiO3 to form a solid solution with perovskite-type structure. A diffuse character was proved by the linear fitting of the modified
Curie-Weiss law. The temperature dependence of dielectric constant at different frequencies revealed that the solid solution
exhibited relaxor characteristics different from classic relaxor ferroelectrics. The samples with x = 0·002 and 0·006 exhibited obvious relaxor characteristics near the low temperature dielectric abnormal peak, T
f, and the samples with x = 0·010 and 0·014 exhibited obvious relaxor characteristics between room temperature and T
f. The mechanism of relaxor behaviour was also discussed according to the macro-domain to micro-domain transition theory. 相似文献
4.
H. Y. Tian K. W. Kwok H. L. W. Chan C. E. Buckley 《Journal of Materials Science》2007,42(23):9750-9755
CuO-doped lead-free ceramics based on bismuth sodium titanate (Bi0.5Na0.5TiO3, BNT) and barium zirconate titanate (Ba(Zr0.07Ti0.93)O3, BZT) were prepared via a multi-step solid-state reaction process. The BNT–BZT with CuO dopant ceramics sintered at 1150–1180 °C
for 2 h in air showed a pure perovskite structure. SEM images reveal that a small amount of CuO (<2 mol%) play a significant
role on the microstructure to improve its sintering attributes, while it will degrade when the dopant is added beyond 2 mol%.
The dielectric and piezoelectric properties of CuO-doped BNT–BZT ceramics were evaluated. At room temperature, the sample
doped with 2 mol% CuO shows quite good properties such as a high piezoelectric constant (d
33 ∼156.5 pC/N) and a high electromechanical coupling factor (k
t ∼52%). The depolarization temperature increased dramatically and the maximum permittivity temperature decreased slightly. 相似文献
5.
The orientation dependence of electromechanical properties of relaxor based ferroelectric single crystals Pb(Zn1/3Nb2/3)O3–(6–7)%PbTiO3 and Pb(Mg1/3Nb2/3)O3–33%PbTiO3 has been calculated by coordinate transformation. Different from previous studies, the optimum cutting orientations have
been predicted in terms of their piezoelectric responses in the corresponding crystal planes. The calculation results indicated
that the anisotropic piezoelectric effects of [001]
c
and [011]
c
poled multi-domain crystals mainly come from the intrinsic contribution. However, the strong dielectric anisotropy of [001]
c
poled multi-domain crystals mainly comes from extrinsic domain and domain wall contributions. For [011]
c
poled multi-domain crystals, the intrinsic orientation effect enhances the dielectric anisotropy. 相似文献
6.
Valence compensated perovskite system Sr1 −x
La
x
Ti1 −x
Co
x
O3 shows dielectric relaxor behaviour with very high value of dielectric constant in the composition range 0·20 <x < 0·40. In this paper the effect of composition on microstructure and the resulting electrical behaviour is reported. The
compositions withx = 0·25, 0·30, 0·33, 0·35 and 0·37 have been synthesized by solid state ceramic method and dielectric measurements were made
in the temperature range of 300–500 K and frequency range of 100 Hz to 1 MHz. Grain boundaries played an important role in
their dielectric behaviour. Complex plane impedance and modulus techniques were used to separate out the contributions of
grain and grain-boundaries to the resulting dielectric behaviour. It was observed that the bulk resistivity as well as the
grain boundaries resistance decreased with increasingx. Furthermore, impedance analysis demonstrated that extremely high value of dielectric constant observed in these materials
was due to barrier layers formation at grain-grain-boundaries interfaces.
Paper presented at the poster session of MRSI AGM VI, Kharagpur, 1995 相似文献
7.
Huanfu Zhou Hong Wang Xiaoyan Ding Xi Yao 《Journal of Materials Science: Materials in Electronics》2009,20(1):39-43
A new Li2O–Nb2O5–TiO2 (LNT) ceramic with the Li2O:Nb2O5:TiO2 mole ratio of 3:1:3 has been investigated. The compound is composed of two phases, the Li2TiO3 and “M-phase” solid solution phase. The microwave dielectric ceramic has low sintering temperature (∼1100 °C) and good microwave
dielectric properties of a relatively high permittivity (∼51), high Q × f value up to 8700, and small temperature coefficient (∼37 ppm/°C). The low-amount doping of 0.83Li2O–0.17V2O5 (LV) can effectively lower the sintering temperature from 1100 to 900 °C and induce no obvious degradation of the microwave
dielectric properties. Typically, the 1 wt.% LV-doped ceramic sintered at 900 °C has better microwave dielectric properties
of εr = 51.3, Q × f = 7235 GHz, τ
f
= 22 ppm/°C, which suggests that the ceramics can be applied in microwave LTCC devices. 相似文献
8.
BYUNG-MOON JIN RUYAN GUO A. S BHALLA SUNG-CHUL KIM 《Journal of Materials Science》1997,32(8):2055-2058
Temperature dependent piezoelectric properties of ferroelectric relaxor single crystals, particularly the cerium-doped strontium
barium niobate compositions (SBN60: Ce), were investigated by resonance and anti-resonance technique. Characteristic resonant
frequencies (fr−fa, fs−fp, and fm−fn) were studied using equivalent circuit simulation. Piezoelectric resonance in a relaxor resonator persists into temperatures
much higher than Tm (the temperature at which dielectric constant, κ, has a maximum at 1 kHz) in comparison with the normal
ferroelectrics such as TGS. The parameters in an equivalent circuit, however, are phenomenally different from a normal resonator
like a TGS, near and above the transition temperature region. The significance and understanding of the piezoelectric resonance
characteristics in ferroelectric relaxor are discussed.
This revised version was published online in November 2006 with corrections to the Cover Date. 相似文献
9.
Perovskite types (1 − x)[PMN–PT(65/35)]–xPZ (with x = 0, 0.1, 0.3, 0.5, 0.7 and 0.9) piezoelectric ceramics were prepared by a modified columbite precursor method. The lattice
parameters of the (1 − x)[PMN–PT(65/35)]–xPZ ceramics increase with the addition of larger Zr4+ ion compared to that of other B-site ions. The SEM photographs of all the samples with different PZ content exhibit homogeneous
and dense microstructure. The P–E loops indicate the PMN–PT–PZ ternary system has excellent ferroelectric properties. Both d
33 and k
p dependences in PZ content show similar variation. Introduction of a small amount of PZ content in the PMN–PT(65/35) ceramics
enhanced the relaxor behavior, which was confirmed by studying frequency and temperature-dependent dielectric behavior. The
increasing values of diffuseness parameter obtained from the fit of a modified Curie–Weiss law established the relaxor nature. 相似文献
10.
Changrong Zhou Xinyu Liu Weizhou Li Changlai Yuan Guohua Chen 《Journal of Materials Science》2009,44(14):3833-3840
Lead-free piezoelectric ceramics (1 − x − y)Bi0.5Na0.5TiO3–xBi0.5K0.5TiO3–yBiCoO3 (x = 0.12–0.24, y = 0–0.04) have been fabricated by a conventional solid-state reaction method, and their structure and electrical properties
have been investigated. The XRD analysis shows that samples with y ≤ 0.03 exhibit a pure perovskite phase and very weak impurity reflections can be detected in the sample with y = 0.04. With x increasing from 0.12 to 0.24 and y increasing from 0 to 0.04, the ceramics transform gradually from a rhombohedral phase to a tetragonal phase and rhombohedral–tetragonal
phase coexistence to a pseudocubic phase, respectively. The morphotropic phase boundary (MPB) of the system between rhombohedral
and tetragonal locates in the range of x = 0.18–0.21, y = 0–0.03. The ceramics near the composition of the MPB have good performances with piezoelectric constant d
33 = 156 pC/N and electromechanical coupling factor k
p = 0.34 at x = 0.21 and y = 0.01, which attains a maximum value in this ternary system. Adding content of BiCoO3 leads to a disappearance of the response in the curves of dielectric constant-temperature to the ferroelectric–antiferroelectric
transition. The temperature dependence of dielectric properties suggests that the ceramics are relaxor ferroelectrics. The
results show that (1 − x − y)Bi0.5Na0.5TiO3–xBi0.5K0.5TiO3–yBiCoO3 ceramics are good candidate for use as lead-free ceramics. 相似文献
11.
Chemically beneficiated high silica/alumina iron ore rejects (27–76% Fe2O3) were used to synthesize iron oxides of purity 96–98% with SiO2/Al2O3 ratio reduced to 0.03. The major impurities on chemical beneficiations were Al, Si, and Mn in the range 2–3%. A 99.73% purity
Fe2O3 was also prepared by solvent extraction method using methyl isobutyl ketone (MIBK) from the acid extracts of the ore rejects.
The magnesium ferrite, MgFe2O4, prepared from these synthetic iron oxides showed high resistivity of ∼ 108 ohm cm. All ferrites showed saturation magnetization, 4πMs, in the narrow range of 900–1200 Gauss and the Curie temperature,T,
cof all these fell within a small limit of 670 ± 30 K. All ferrites had low dielectric constants (ε′), 12–15, and low dielectric
loss, tan δ, which decreased with the increase in frequency indicating a normal dielectric dispersion found in ferrites. The
presence of insignificant amount of polarizable Fe2+ ions can be attributed to their high resistances and low dielectric constants. Impurities inherent in the samples had no
marked influence on the electrical properties of the ferrites prepared from the iron ore rejects, suggesting the possibility
of formation of ferrite of constant composition, MgFe2O4, of low magnetic and dielectric losses at lower temperatures of 1000°C by ceramic technique. 相似文献
12.
Lead-free (1 − x)K0.5Na0.5NbO3–xCaTi0.9Zr0.1O3 + 0.75 mol%MnO2 piezoelectric ceramics have been prepared by an ordinary sintering technique and their phase transition, dielectric and piezoelectric
properties have been studied. The results of X-ray diffraction show that CaTi0.9Zr0.1O3 diffuse into K0.5Na0.5NbO3 lattices to form a solid solution with a perovskite structure. After the addition of CaTi0.9Zr0.1O3, both the cubic–tetragonal and tetragonal–orthorhombic phase transition temperatures decrease, and a relaxor behavior is
induced. Coexistence of the orthorhombic and tetragonal phases is formed in the ceramics with 0.03 < x < 0.07 at room temperature. Owing to the higher number of possible polarization states resulting from the coexistence of
the two phases, the piezoelectric properties of the ceramics are enhanced significantly. The ceramic with x = 0.05 exhibits the following optimum properties: d
33 = 203 pC/N, k
p = 45.0%, and T
C = 342 °C. 相似文献
13.
A. N. Patil M. G. Patil K. K. Patankar V. L. Mathe R. P. Mahajan S. A. Patil 《Bulletin of Materials Science》2000,23(5):447-452
The dielectric properties (dielectric constant and loss) for the system Cu
x
Fe3−x
O4 with x = 1.0, 0.8, 0.6, 0.4 and 0.2, were studied in the temperature range 300 ∼ 800 K and also in the frequency range 1
kHz ∼ 1 MHz. A.c. conductivity was derived from dielectric constant and loss tangent data. The conduction in this system is
interpreted as due to small polaron hopping. The dielectric relaxation was observed for the compositions with tetragonal structure
whereas normal behaviour was observed for cubic structure. 相似文献
14.
Lead-free piezoelectric ceramics (1 − x)Bi0.5Na0.5TiO3–xBaNb2O6 (BNT–BN100x), a new member of the BNT-based group, was prepared by conventional solid state reaction. X-ray diffraction showed that BaNb2O6 (BN) diffused into the lattice of Bi0.5Na0.5TiO3 to form a solid solution with perovskite-type structure. The temperature dependence of dielectric constant εr revealed that the solid solution underwent two phase transitions from ferroelectric to anti-ferroelectric and anti-ferroelectric
to paraelectric. Both the transition temperature T
d and T
m were shifted to lower with the increasing content of BaNb2O6. The temperature dependence of dielectric constant at different frequency revealed that the solid solution exhibited obviously
dielectric relaxation characteristics. The sample with x = 0.6 mol% exhibited excellent electrical properties, piezoelectric constant d
33 = 94 pC/N; electromechanical coupling factor k
p = 0.185. The results showed that BNT–BN100x ceramics were good candidates for use as lead-free piezoelectric ceramics. 相似文献
15.
O. V. Ovchar D. A. Durilin A. G. Belous Bostjan Jancar Matjaz Spreitzer Danilo Suvorov 《Inorganic Materials》2011,47(11):1238-1241
We report the preparation and characterization of AgNb0.6Ta0.4O3 (ANT) based materials. The addition of Zn2TiO4 and ZnB2O4 influences the sintering temperature, phase composition, and microstructure of ANT ceramics. ANT doped with 1 wt % Zn2TiO4 or ZnB2O4 has high dielectric permittivity (400–470), low dielectric losses (tanδ ∼ 10−3), and a nonlinearity coefficient n
R
≅ 3–9% (at a field strength E = 3 × 106 V/m). 相似文献
16.
Temperature and frequency dependence dielectric permittivity of Ba0·95Dy0·05TiO3 ceramic has been studied in the temperature range of 100–350 K at the frequencies, 1 kHz, 10 kHz, 100 kHz and 1 mHz. Diffuse
phase transition and frequency dispersion is observed in the permittivity-vs-temperature plots. This has been attributed to
the occurrence of relaxor ferroelectric behaviour. The observed relaxor behaviour has been quantitatively characterized based
on phenomenological parameters. A comparison with the Zr doped BaTiO3 has also been presented. The microstructure of as-sintered samples shows a dense and almost uniform micrograph without any
impurity phases; the grains are almost spherical with random orientation. 相似文献
17.
Preparation and properties of ceramics based on (Na0.5Bi0.5)1 ? xAxTiO3 (A = Sr, Cd) solid solutions
This paper describes the preparation and properties of (Na0.5Bi0.5)1 − x
A
x
TiO3 (A = Sr, Cd) lead-free ferroelectric ceramics. The (0.63–0.66)Na0.5Bi0.5TiO3 · (0.37–0.34)Sr0.7Bi0.2TiO3 ceramics are shown to have the best dielectric and piezoelectric properties: tanδ = 0.013–0.009, ɛRT = 1200–1500, d
31 = (370–400) × 10−12 C/N, and k
ρ = 0.4–0.58. The cadmium-containing ceramics offer low dielectric losses and high dielectric permittivity at room temperature. 相似文献
18.
Daojiang Gao K. W. Kwok Dunmin Lin H. L. W. Chan 《Journal of Materials Science》2009,44(10):2466-2470
CeO2-doped K0.5Na0.5NbO3 lead-free piezoelectric ceramics have been fabricated by a conventional ceramic fabrication technique. The ceramics retain
the orthorhombic perovskite structure at low doping levels (<1 mol.%). Our results also demonstrate that the Ce-doping can
suppress the grain growth, promote the densification, decrease the ferroelectric–paraelectric phase transition temperature
(T
C), and improve the dielectric and piezoelectric properties. For the ceramic doped with 0.75 mol.% CeO2, the dielectric and piezoelectric properties become optimum: piezoelectric coefficient d
33 = 130 pC/N, planar electromechanical coupling coefficient k
p = 0.38, relative permittivity εr = 820, and loss tangent tanδ = 3%. 相似文献
19.
Ch. Sameera Devi M. Vithal G. S. Kumar G. Prasad 《Journal of Materials Science: Materials in Electronics》2011,22(12):1855-1864
Lead free (Ba(1−3x)Nd(2x))(Ti(1−y)Zry)O3 (x = 0, 0.025, y = 0, 0.025, 0.05) ceramics were prepared successfully using sol–gel method. The effect of Nd, Zr content
on dielectric and polarisation properties of BaTiO3 were studied using dielectric and hysteresis measurements. SEM analysis proved that the particle size of compounds as prepared
were in the order of 30–60 nm. The ferroelectric phase transition from tetragonal to cubic phase was observed around 130 °C
for pure BaTiO3. With the addition of Nd (2.5 mol%) and increasing content of Zr (2.5 and 5 mol%), it was observed that transition temperature
(Tc) shifts to lower temperatures (70–50 °C), but didn’t show any relaxor behaviour. Dielectric measurements showed an increase
in the values at room temperature in all the doped samples. The synthesized ceramics exhibited typical P–E hysteresis loops
at room temperature accompanied by saturation polarisation (Ps) and remanent polarisation (Pr). Behaviour of polarisation phenomena in these compounds showed interesting results with increasing temperature. 相似文献
20.
The DC electrical resistivity results of La4 −x
Sr1 +x
Cu5 −x
Fe
x
O12 + δ (0 ≤x ≤ 1·0) showed that for S1 (x = 0) and S2 (x = 0·25) the temperature coefficient of resistivity (TCR), dρ/dT, is positive and slightly increases with increasing temperature in the range 20–270 K. This shows the metallic nature of
S1 and S2. For the samples S3(x = 0·5) and S4 (x = 0·75), TCR slightly increases in the range 20–270 K, with change in sign from negative to positive at ∼ 80 K and ∼ 130
K, respectively. These results show the metal-insulator type transition in S3 and S4. For the sample S5 (x = 1·0), the TCR is negative and gradually increases in the range 20–270 K, which shows its semiconductor-like behaviour.
The activation energy for S5 is found to be 0·21 × 10−2 eV. Furthermore, the DC resistivity results of S1–S5 in the range 350–660 K are in conformity with the low temperature results.
The very weak temperature dependence of magnetic susceptibility results of S1–S3 show Pauli-paramagnetic behaviour in the
range 77K–400 K, while S4 and S5 exhibit Pauli-paramagnetic behaviour in the range 77–850 K. Long-range antiferromagnetic
interaction is observed in S5 (x = 1·0) belowT
c ∼ 100 K. The room temperature EPR lineshapes gradually improve from metallic S1 (x = 0) to semiconductor-like S5(x = 1·0). Negativeg-shift is observed in the samples S2–S5 with increasing trend ing
iso-values of 1·880 in S2 to 1·961 in S5. However, theg
iso-value for S1 could not be observed due to very poor lineshape. 相似文献