共查询到20条相似文献,搜索用时 31 毫秒
1.
Wanwimon Banlue Naratip Vittayakorn Chien-Chih Huang David P. Cann 《Journal of Materials Science》2008,43(12):4220-4225
Polycrystalline samples of Pb[(1 − x)(Zr1/2Ti1/2) − x(Zn1/3Ta2/3)]O
3
, where x = 0.1–0.5 were prepared by the columbite and wolframite methods. The crystal structure, microstructure, and dielectric properties
of the sintered ceramics were investigated as a function of composition via X-ray diffraction (XRD), scanning electron microscopy
(SEM), and dielectric spectroscopy. The results indicated that the presence of Pb(Zn1/3Ta2/3)O3 (PZnTa) in the solid solution decreased the structural stability of overall perovskite phase. A transition from tetragonal
to pseudo-cubic symmetry was observed as the PZnTa content increased and a co-existence of tetragonal and pseudo-cubic phases
was observed at a composition close to x = 0.1. Examination of the dielectric spectra indicated that PZT–PZnTa exhibited an extremely high relative permittivity at
the MPB composition. The permittivity showed a ferroelectric to paraelectric phase transition at 330 °C with a maximum value
of 19,600 at 100 Hz at the MPB composition. 相似文献
2.
S. Jesurani S. Kanagesan T. Kalaivani K. Ashok 《Journal of Materials Science: Materials in Electronics》2012,23(3):692-696
The dielectric properties of Erbium doped CaCu3Ti(4–x)ErxO(12–δ) with x = 0, 0.05, 0.1 were synthesized by the sol–gel self combustion method. XRD (X-ray powder diffraction) analysis confirmed
the formation of single-phase material in the samples calcined at 800 °C. Crystal structure does not change on doping with
Erbium and it remains cubic in all the three compositions studied. It is found that lattice parameter increases slightly with
Erbium doping. The surface morphology of CaCu3Ti(4–x)ErxO(12–δ) powders sintered at 950 °C in air for 3 h was observed using high resolution—scanning electron microscope and it shows that
the grain size is in the range of 1–8 μm for these samples. Energy dispersive X-ray spectroscopy pattern confirmed the presence
of Erbium with 1.9 and 4.86 atomic percentages with doping concentration. The dielectric characteristics of CaCu3Ti(4–x)ErxO(12–δ) were studied by LCR meter in the frequency range (100 Hz–1 MHz) at various temperatures (RT to 500 °C). Interestingly, the
dielectric constant increases and dielectric loss had lower values than those of undoped CCTO. 相似文献
3.
4.
Wenfeng Liang Wenjuan Wu Dingquan Xiao Jianguo Zhu Jiagang Wu 《Journal of Materials Science》2011,46(21):6871-6876
0.94(K0.4−x
Na0.6Ba
x
Nb1−x
Zr
x
)O3–0.06LiSbO3 ceramics were prepared by conventional technique, and the effect of BaZrO3 on the phase transitions, dielectric, ferroelectric, and piezoelectric properties of the ceramics were investigated. The
phase transitions for the ceramics were determined by the temperature dependence of dielectric properties and X-ray diffraction
patterns. BaZrO3 changes the symmetry of the ceramics from tetragonal dominant phase with x = 0–0.06 to rhombohedral phase with x = 0.07–0.09. The phase transition near room temperature for the composition with x ~ 0.06 is different from previously reported phase transition between orthorhombic and tetragonal phases. It is suggested
that a new morphotropic phase boundary (MPB) is constructed with both rhombohedral–orthorhombic and orthorhombic–tetragonal
phase transitions near room temperature, and the enhanced piezoelectric properties (d
33 = 344 pC/N and k
P = 32.4% with x = 0.06) are obtained. The results indicate that the construction of new MPB is of significance for further development of
KNN-based ceramics. 相似文献
5.
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
6.
Guo-hua Chen Jun-tao Liu Hua-rui Xu Chang-rong Zhou Min-hong Jiang Xin-yu Liu 《Journal of Materials Science: Materials in Electronics》2011,22(8):915-919
Ultrafine strontium barium niobate (Sr0.3Ba0.7Nb2O6, SBN30) powders were prepared by urea method starting from a precursor solution constituting of Sr (NO3)2, Ba (NO3)2, NbF5, urea and polyvinyl alcohol (PVA) as surfactant. Their structural behavior and morphology were examined by means of X-ray
diffractometry (XRD) and Scanning electron microscopy (SEM). The results showed that the SBN30 powders crystallized to a pure
tetragonal phase at annealing temperatures as low as 750 °C. The average particle size of SBN powders subjected to 750 °C
was of the order of 150–300 nm. With increasing calcination temperature,however, the average particle size of the calcined
powders increased. The SBN30 ceramic prepared from urea method can be sintered at temperature as low as 1,225 °C. The transition
temperature from the ferroelectric phase to the paraelectric phase and the relative dielectric permittivity of the SBN30 powder
were less than the corresponding values of the bulk ceramic. The permittivity and loss tangent (tan δ) at room temperature
(1 kHz) was found to be 930 and below 0.025. 相似文献
7.
Yih-Chien Chen Shi-Li Yao 《Journal of Materials Science: Materials in Electronics》2012,23(4):825-831
The influence of Ca0.8Sr0.2TiO3 on the microstructures and microwave dielectric properties of Nd(Mg0.4Zn0.1Sn0.5)O3 ceramics were investigated by the conventional solid-state method. The X-ray diffraction peaks of (1 − x)Nd(Mg0.4Zn0.1Sn0.5)O3–xCa0.8Sr0.2TiO3 ceramic system shifted to higher angles as x increased. The dielectric constant increased from 31.8 to 47.7, the quality factor (Q × f) decreased from 54,200 to 42,800 GHz, and the temperature coefficient of resonant frequency (τ
f
) increased from −43 to +41 ppm/°C as x increased from 0.5 to 0.7 when (1 − x)Nd(Mg0.4Zn0.1Sn0.5)O3–xCa0.8Sr0.2TiO3 ceramic system sintered at 1,600 °C for 4 h. 相似文献
8.
A two-step sintering approach composed of spark-plasma-sintering (SPS) technique at 1000 °C for 1 min and under a uniaxial
pressure of 63 MPa followed by conventional sintering at 1400 °C for 3 h is proposed for synthesis of dense Ba(Ti0.87Sn0.13)O3 ceramics. Starting powders had grain size of about 90 nm and were obtained by co-precipitation. The SPS pellets consist of
submicron (300–500 nm) grains. X-ray diffraction analysis of as-prepared Ba(Ti0.87Sn0.13)O3 ceramic shows the occurrence of cubic and tetragonal phase coexistence for the pellets obtained after SPS processing and
the presence of only tetragonal phase in the samples after the second (conventional) sintering. Grain uniformity in the final
product is high, with average size of ~2 μm. The apparent densities of the sintered pellets at temperature of 1400 °C were
~92% of the theoretical value of Ba(Ti0.87Sn0.13)O3. The ceramics exhibit a high relative dielectric constant of 6,550 and a dielectric loss (tan δ) = 0.078 at Curie temperature
of 63 °C and 10 Hz. 相似文献
9.
The low-temperature confirmable Ba6−3x
R8+2x
Ti18O54 (BNT, R = Nd, x = 2/3) ceramics were prepared by means of a citrate sol–gel soft-chemical method and the addition of sintering aid. Nano-sized
BNT crystallite powders (~80 nm) were successfully synthesized as indicated by transmission electron microscopy and X-ray
diffractometry. The powder compacts exhibit enhanced sintering activity and can be well densified at 925 °C with the aid of
a small amount of CuO and B2O3. Compared to pure BNT ceramics prepared by a solid-state reaction method, not only was the sintering temperature significantly
decreased, but also the good microwave dielectric properties of dielectric constant εr = 63 and quality factor Q × f = 5200 GHz were maintained. Moreover, the relationship between the microstructure, densification, and electrical properties
was discussed. 相似文献
10.
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
11.
Hiroyuki Sasakura Yoshiya Akagi Masashi Tanaka Shigeki Tsukui Motoaki Adachi 《Journal of Superconductivity and Novel Magnetism》2012,25(2):305-309
New Pb-based 1222 cuprates containing phosphorus have been synthesized in the (Pb0.75P0.25)Sr2- (RE2–x–y
Ce
x
Sr
y
)Cu2O
z
(RE = Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb, and Y) systems. The almost-single phase samples are obtained for 0.5≤x≤1.0 and y=0.1 in the cases of RE = Nd, Dy, Ho, Er, Tm, Yb and Y, while for 0.3≤x≤1.0 and y=0.1 in the cases of RE = Sm, Eu and Gd. The samples crystallize in a tetragonal lattice, the lattice parameters a and c are decreasing with the decrease of the ionic radius of the RE element. Even after annealing under 143 atm O2 atmosphere at 400 °C, almost all the samples with the common values x=0.5 and y=0.1 are semiconductors with a transport process followed by three-dimensional variable range hopping. However, the samples
of RE = Sm, Eu and Gd, which are of almost single 1222 phase, even for x=0.3 and y=0.1, show superconductivity with the onsets at about 25 K, 20 K and 22 K, respectively. Through this study, we find very
important procedure for discovery of new superconducting 1222 compound. 相似文献
12.
Xiaozan Guo Yugong Wu Yanan Zou Zhiyuan Wang 《Journal of Materials Science: Materials in Electronics》2012,23(5):1072-1076
Samples of xBiFeO3–(1 − x)BaTiO3 (x = 0, 0.02, 0.04, 0.06, 0.07 and 0.08) were synthesized by solid state reaction technique and sintered in air in the temperature
range 1,220–1,280 °C for 4 h. X-ray diffraction data showed that 2–8 mol% BiFeO3 can dissolve into the lattice of BaTiO3 and form single perovskite phase. The crystal structure changes from tetragonal to cubic phase at room temperature when 8 mol%
of BiFeO3 was added into BaTiO3. Scanning electron microscope images indicated that the ceramics have compact and uniform microstructures, and the grain
size of the ceramics decreases with the increase of BiFeO3 content. Dielectric constants were measured as functions of temperatures (25–200 °C). With rising addition of BiFeO3, the Curie temperature decreases. For the sample with x = 0.08, the phase transition occurred below room temperature. The boundary between tetragonal and cubic phase of the BiFeO3–BaTiO3 system at room temperature locates at a composition between 7 and 8 mol% of BiFeO3. The diffusivity parameter γ for compositions x = 0.02 and x = 0.07 is 1.21 and 1.29, respectively. The relaxor-like behaviour is enhanced by the BiFeO3 addition. 相似文献
13.
Om Parkash Devendra Kumar R. K. Dwivedi K. K. Srivastava Prakash Singh Sindhu Singh 《Journal of Materials Science》2007,42(14):5490-5496
A few compositions in the valence compensated system Ba1−x
La
x
Ti1−x
Mn
x
O3 were synthesized by solid-state ceramic method to study the effect of co-doping lanthanum and manganese in equimolar amounts
on dielectric behavior of BaTiO3. Compositions with x ≤ 0.10 have shown solid solution formation. Compositions with x ≤ 0.05 are found to have tetragonal structure at room temperature while composition with x = 0.10 is cubic. Plots of relative dielectric constant, εr versus temperature for composition with x = 0.01 show dielectric anomalies around 376 ± 2, 264 ± 2 and 179 ± 2 K which correspond to cubic to tetragonal (T
C–T), tetragonal to orthorhombic (T
T–O) and orthorhombic to rhombohedral (T
O–R) transition, respectively, similar to BaTiO3. Curie temperature has been found to decrease with increasing concentration of lanthanum and manganese simultaneously in
barium titanate. The broadening in the dielectric peak at cubic to tetragonal (T
C–T) transition temperature increases with increasing x. For x = 0.10, only one anomaly at 100 K is observed in its εr versus T plots. The observation of this single anomaly may be due to pinching effect of the substitutions on the three phase transitions. 相似文献
14.
Archana Shukla R. N. P. Choudhary A. K. Thakur 《Journal of Materials Science: Materials in Electronics》2009,20(8):745-755
Polycrystalline samples of Mn-modified lead titanate (Pb Mn
x
Ti1−x
O3 (PMT) with x = 0, 0.04, 0.07, 0.10) were prepared by a high-temperature solid-state reaction method. Calcination and sintering temperatures
were optimized by thermal gravimetric analysis and repeated firing. Preliminary structural studies using an X-ray diffraction
technique (at room temperature) suggest that compounds are formed in a single phase with tetragonal crystal system. Scanning
electron micrographs show uniform grain distribution throughout the surface of the samples. Detailed studies of dielectric
and impedance properties of the compounds in a wide range of temperature (35 °C–500 °C) and frequency range (1 kHz–1 MHz)
exhibit that phase transition temperature of the PMT compounds depends on Mn concentration. The real and imaginary part of
complex impedance plots exhibit semicircle(s) in the complex plane. The temperature dependent plots reveal the presence of
both bulk and grain boundary effects at high-temperature. The bulk resistance of the material decreases with rise in temperatures.
This exhibits a typical negative temperature coefficient of resistance behaviour of the material. 相似文献
15.
R. N. P. Choudhary Dillip K. Pradhan C. M. Tirado G. E. Bonilla R. S. Katiyar 《Journal of Materials Science》2007,42(17):7423-7432
The nanocrystalline fine powders (∼80 nm) of (Ba1−x
La
x
)(Fe2/3W1/3)1−x/4O3, (BLFW) (x = 0.0, 0.05, 0.10 and 0.15) were synthesized with a combined mechanical activation and conventional high-temperature solid-state
reaction methods. Preliminary X-ray structural analysis of pellet samples (prepared from fine powders) showed formation of
a single-phase tetragonal system. Detailed studies of dielectric properties (εr and tan δ) exhibit that these parameters are strongly dependent on frequency, temperature and La composition. The La-substitution
increases the dielectric constant and decreases the tan δ up to 10% substitutions of La at the Ba-site, and then reversed
the variation, and hence this composition is considered as a critical composition. This observation was found valid for structure,
microstructures, dielectric constant, electrical conductivity, J–E characteristics and impedance parameters also. Like in other perovskites (PZT, BZT), La substitution plays an important role
in tailoring the properties of Ba(Fe2/3W1/3)O3 ceramics. 相似文献
16.
The dielectric, ferroelectric, and piezoelectric properties of ceramic materials of compositions (1 − x)[Pb0.91La0.09(Zr0.60Ti0.40)O3]–x[Pb(Mg1/3Nb2/3)O3], x = (0, 0.2, 0.4, 0.6, 0.8, and 1.0) were studied. The above compositions were prepared by mixing the individual Pb0.91La0.09(Zr0.60Ti0.40)O3 (PLZT) and Pb(Mg1/3Nb2/3)O3 (PMN) powders in order to design materials with different combination of piezo and dielectric properties. The powders were
calcined at 850 °C for 4 h. The presence of various phases in the calcined powders was characterized by X-ray diffraction
(XRD) technique. The compacts were prepared by uniaxial pressing and were sintered at 1250 °C for 2 h. The sintered compacts
were electroded, poled at 2 kV/mm dc voltage and their dielectric, ferroelectric, and piezoelectric properties were measured.
In general, it was observed that the dielectric constant, loss factor and the slimness of the ferroelectric curves increase
with the PMN content while the remnant polarization, saturation polarization, and the coercive fields were decreased. It is
now possible to design materials with a wide combination of d
33, K, and loss factor by varying PLZT and PMN ratio. 相似文献
17.
Feng Jianqing Lu Yafeng Zhou Lian Zhang Pingxiang Xu Xiaoyan Chen Shaokai Zhang Cuiping Xiong Xiaomei Liu Guoqing 《Journal of Materials Science: Materials in Electronics》2008,19(11):1069-1072
The effects of heating rate and holding time on the formation of YBa2Cu3O7−x
phase in precursor powders for YBa2Cu3O7−x
superconducting bulks prepared by powder melting process have been investigated. The phase conversion of the precursor powders
is studied by X-ray diffraction and found to be different for different heating rates during heating. The YBa2Cu3O7−x
phase is formed during heating to peritectic temperature at 100 and 400 °C/h, but not at 6,000 °C/h. The longer the holding
time, the more the amount of YBa2Cu3O7−x
phase between 880 °C and about 950 °C. The results are useful for understanding the mechanism of powder melting process and
controlling the process conditions. 相似文献
18.
Tao Li Kun Yang Renzhong Xue Yuncai Xue Zhenping Chen 《Journal of Materials Science: Materials in Electronics》2011,22(7):838-842
(1 − x) BaTiO3/xCuO ceramic pellets with x = 0, 0.2, 0.4, 0.6, and 0.8% respectively were prepared by the traditional solid-state reaction method. The effect of CuO
doping on the microstructure and dielectric properties of BaTiO3 ceramics has been investigated. SEM and XRD results at room temperature show that the grain size grows with the increase
of CuO content under the same sintering conditions and the crystal structure undergoes the mixed phases (pseudocubic/tetragonal)
to tetragonal phase transition with the growth of grain size. Regular shape grains with average grain size ~2 μm are detectable
in the specimens as CuO dopant content adds up to 0.8% and the crystal structure has completely changed into tetragonal phase.
The permittivity increases markedly for CuO dopant content x = 0.2 ~ 0.4% and the dielectric loss decreases significantly after being doped by CuO and down to a minimum value for x = 0.8%. In addition, the permittivity and dielectric loss display a good stability in a broad frequency range comparing that
of pure BaTiO3 ceramics. 相似文献
19.
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
20.
Crystallization of coprecipitated PbTiO3 powder was studied by calcining as-precipitated powders at 400–800 °C for up to 262 h. The coprecipitated powders were prepared
from a solution containing a 1∶1 molar ratio of Pb(NO3)2∶TiCl4 and a 1.1∶1 molar ratio of H2O2∶TiCl4. The solution containing the lead and titanium complexes was slowly added to NH4OH solution under constant pH (10.00±0.05) conditions that induced precipitation. Transmission electron microscopy and X-ray
diffraction indicated that the calcined powders consisted of an intimate mixture of amorphous, cubic (or distorted tetragonal
withc
0/a
0<1.01), and tetragonal (c
0/a
0=1.065) PbTiO3 particles between 10 and 400 nm, with both particle size and phase content depending on heat treatment. Powders exhibiting
the cubic or distorted tetragonal phase consisted of particles between 20 and 200 nm in diameter. Fully crystalline tetragonal
PbTiO3 powders consisting of 100–400 nm particles were prepared. 相似文献