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1.
Microstructure, phase transition and electrical properties of (1 − x)K0.49Na0.51NbO3 − xLiSbO3 (x = 0–0.08) lead-free piezoceramics prepared by the conventional solid-state sintering method were investigated with an emphasis
on the effects of LiSbO3 doping amount x. SEM results showed that the ceramic became denser by increasing LiSbO3 doping amount x. Being indexed by XRD profiles, the ceramics changed from an orthorhombic perovskite structure to a tetragonal one across
a composition region of 0.04 ≤ x≤0.05. The sample of LiSbO3 doping amount x = 0.05 in tetragonal side of the region had the maximum values of piezoelectric constant (d
33 = 256 pC/N) and planar electromechanical coupling coefficient (k
p = 42.7%). Meanwhile, this ceramic sample showed other good properties such as ε
r = 1,463, tgδ = 0.036, Q
m = 48, P
r = 19.8 μC/cm2, E
c = 1.9 kV/mm and T
c = 340 °C, which indicated it was a promising lead-free piezoelectric material for ultrasonic transducer applications. 相似文献
2.
Jian Wang Hong Zhang Yiyu Li Zhicheng Li 《Journal of Materials Science: Materials in Electronics》2010,21(8):811-816
BaTi1−x
Co
x
O3−δ (0.01 ≤ x ≤ 0.4) ceramics were prepared by a wet chemical process polymerized with polyvinyl alcohol. The phases and related electrical
properties of the ceramics were investigated. The phase component of the ceramics changes from a tetragonal phase to a hexagonal
one with the Co concentration increase. A pure hexagonal phase formed in the ceramic with x = 0.2. The measurement of the temperature dependence of resistances revealed that the ceramic resistivities increase with
temperature rising at the temperatures (T) lower than half of the related Debye temperature (ΘD), and the ceramics show a negative temperature coefficient (NTC) effect at T > ΘD/2. The material constants B
50/120 of the BaTi1−x
Co
x
O3−δ NTC thermistors were calculated to be 3,187, 2,968 and 2,648 K for x = 0.2, 0.3 and 0.4, respectively. Narrow-band conduction and non-adiabatic hopping models are proposed for the conduction
mechanisms at T < ΘD/2 and T > ΘD/2, respectively. 相似文献
3.
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
4.
A. I. Shames E. Rozenberg C. Martin A. Maignan B. Raveau G. André G. Gorodetsky 《Journal of Superconductivity and Novel Magnetism》2007,20(2):99-103
Electron magnetic resonance (EMR), neutron powder diffraction (NPD) and ac susceptibility techniques were employed for studying
the crystallographic structure and magnetic ordering in CaMn1−xRuxO3 (x ≤ 0.40) manganite system. EMR measurements were done on polycrystalline samples at 120 ≤ T ≤ 500 K. High temperature EMR
spectra of pristine antiferromagnetic (AFM) CaMnO3 show a singlet Lorentzian-like line, whose intensity diminishes, zeroing at Neel temperature T
N=120 K. Strong broadening of paramagnetic (PM) lines with increase of Ru-content (Δ Hpp ∼ 1 T for x=0.10) was found. Upon cooling low-doped (x ≤ 0.06) samples remain AFM, whereas higher doped ones (0.10 ≤ x ≤ 0.40) clearly
show progressive appearance of ferromagnetic (FM) phases. Thus, EMR evidences that Ru-doping modifies both PM and AFM states
and creates an inhomogeneous phase separated FM and AFM ground states at x0.06. Complementary measurements of NPD and ac susceptibility corroborate the complex character of magnetic ordering, revealed
by EMR. The changes of the magnetic ordering in CaMn1−xRuxO3 supposed to be solely determined by doping of Mn-sites with Ru. 相似文献
5.
Dunmin Lin Qiaoji Zheng K. W. Kwok Chenggang Xu Chun Yang 《Journal of Materials Science: Materials in Electronics》2010,21(7):649-655
Lead-free MnO2-doped K0.5Na0.5Nb0.92Sb0.08O3 ceramics have been fabricated by a conventional ceramic technique and their dielectric and piezoelectric properties have
been studied. Our results show that a small amount of MnO2 (0.5–1.0 mol%) is enough to improve the densification of the ceramics and decrease the sintering temperature of the ceramics.
The co-effects of MnO2 doping and Sb-substitution lead to significant improvements in the ferroelectric and piezoelectric properties. The K0.5Na0.5Nb0.92Sb0.08O3 ceramic with 0.5 mol%MnO2 doping possesses optimum propeties: d
33 = 187 pC/N, k
P = 47.2%, ε
r = 980, tanδ = 2.71% and T
c = 287 °C. Due to high tetragonal-orthorhombic phase transition temperature (T
O-T ~ 150 °C), the K0.5Na0.5Nb0.92Sb0.08O3 ceramic with 0.5 mol%MnO2 doping exhibits a good thermal stability of piezoelectric properties. 相似文献
6.
Guo-hua Chen Jie-chang Di Ming Li Ian M. Reaney Yan Lei Hua-rui Xu Chang-rong Zhou Min-hong Jiang Xin-yu Liu 《Journal of Materials Science: Materials in Electronics》2012,23(3):746-752
Ca4-xMgxLa2Ti5O17
ceramics were prepared by a solid state ceramic route for x = 0, 0.5, 1, 2, 3 and 4. The structure and microstructure of the ceramics were investigated using X-ray diffraction, scanning
electron microscopy and energy dispersive X-ray spectroscopy. X-ray diffraction results show that the Ca4-x
Mg
x
La2Ti5O17 adopts an orthorhombic crystal structure with no secondary phase observed for x from 0 to 0.5. Secondary phase, MgTiO3 occurs with further increasing doping level (1 ≤ x ≤ 3). When x = 4, mixture phases La0.66TiO2.993, MgTiO3 and a trace of unknown phase coexist. Ca4La2Ti5O17 ceramic exhibits a relative permittivity (εr) ~ 65, quality factor (Q × f) ~13,338 GHz (at ~4.75 GHz), and temperature coefficient of resonant frequency (τ
f
) ~ 165 ppm/°C. The sintering temperature was distinctly reduced from 1,580 °C for x = 0 to 1,350 °C for x = 4. With increasing Mg content, εr and τf obviously decrease, while Q × f value initially decreases and then increases. The ceramic for x = 2 shows εr ~ 50, Q × f ~ 9,451 and τ
f
~ 62.5 ppm/°C. By the complete replacement of Ca with Mg, Mg4La2Ti5O17 ceramic sintered at 1,350 °C for 4 h combines a high dielectric permittivity (ε
r
= 31), high quality factor (Q × f ~ 15,021) and near-zero temperature coefficient of resonant frequency (τ
f
~ 4.0 ppm/°C). The materials are suitable for microwave applications. 相似文献
7.
New dielectric ceramics in the SrLa4−xSmxTi5O17 (0 ≤ x ≤ 4) composition series were prepared through a solid state mixed oxide route to investigate the effect of Sm+3 substitution for La+3 on the phase, microstructure and microwave dielectric properties. At x = 0–3, all the compositions formed single phase ceramics
within the detection limit of in-house X-ray diffraction when sintered in the temperature range 1500–1580 °C. At x = 4, a
mixture of Sm2Ti2O7 and SrTiO3 formed. The maximum Sm+3-containing single phase ceramics, SrLaSm3Ti5O17, exhibited relative permittivity (εr) = 42.6, temperature coefficient of resonant frequency (τ
f
) = −96 ppm/oC and quality factor (Q
u
f
o
) = 7332 GHz. An analysis of results presented here indicates that SrLa4−xSmxTi5O17 ceramics, exhibiting τ
f
~ 0 and εr ~ 53 could be achieved at x ~ 1.4 but at the cost of decrease in Q
u
f
o
. 相似文献
8.
N. G. Margiani I. R. Metskhvarishvili I. A. Mzhavanadze N. A. Papunashvili V. V. Zhghamadze 《Journal of Superconductivity and Novel Magnetism》2010,23(4):531-533
The effect of B2O3 addition on the superconducting transition and grain boundary critical current density of the boron free (control) and boron
doped HTS ceramics with nominal composition YBa2Cu3B
x
O7−y
(x=0, 0.025, 0.05, 0.075, 0.1 and 0.15) has been investigated. For the lowest-level boron doping (x=0.025) an increase by nearly 1.5 times was observed in the critical current density J
c
compared to the control sample. The small additives of boron in YBa2Cu3B
x
O7−y
(x=0.025 and 0.05) do not essentially affect the critical temperature T
c
=92.5 K of nominally pure Y123. Higher-level boron added compounds revealed a decrease in both T
c
and J
c
values. The data obtained indicate the possibility of boron dopant being inserted either into interstitial or into substitutional
sites of the lattice. 相似文献
9.
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
10.
Xuming Pang Jinhao Qiu Kongjun Zhu Jianzhou Du 《Journal of Materials Science: Materials in Electronics》2012,23(5):1083-1086
K0.5Na0.5NbO3–x ZnO (KNN–xZn) lead-free ceramics have been prepared using the conventional sintering technique and the effects of ZnO addition on the
phase structure and piezoelectric properties of the ceramics have been studied. Our results reveal that a small amount of
ZnO can improve the density of the ceramics effectively. Because of the high density and ZnO doping effects, the piezoelectric
and dielectric properties of the ceramics are improved considerably. The good piezoelectric and dielectric properties of d
33 = 114 pC/N, k
p = 0.36, ε
r = 395, and Q
m = 68 were obtained for the KNN ceramics doped with 1 mol% ZnO. Therefore, the KNN-1.0 mol%Zn ceramics is a good candidate
for lead-free piezoelectric application. 相似文献
11.
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
12.
Suhua Fan Fengqing Zhang Guitao Liu Qingbo Tian Luyi Zhu 《Journal of Materials Science: Materials in Electronics》2011,22(12):1778-1782
Bismuth-layered compound Ca0.15Sr1.85Bi4−xNdxTi5O18 (CSBNT, x = 0–0.25) ferroelectric ceramics samples were prepared by solid-state reaction method. The effects of Nd3+ doping on their ferroelectric and dielectric properties were investigated. The remnant polarization Pr of CSBNT ceramics
increases at beginning then decreases with increasing of Nd3+ doping level, and a maximum Pr value of 9.6 μC/cm2 at x = 0.05 was detected with a coercive field Ec = 80.2 kV/cm. Nd3+ dopant not only decreases the Curie temperature linearly, but also the dielectric constant (εr) and dielectric loss tangent (tan δ). The magnitudes of εr and tan δ at the frequency of 100 kHz are estimated to be 164 and 0.0083 at room temperature, respectively. 相似文献
13.
Roberto Köferstein Lothar Jäger Mandy Zenkner Francisco Javier García-García Stefan G. Ebbinghaus 《Journal of Materials Science》2010,45(14):3784-3790
The formation of solid solutions of the type [Ba(HOC2H4OH)4][Sn1−x
Ge
x
(OC2H4O)3] as BaSn1−x
/Ge
x
O3 precursor and the phase evolution during its thermal decomposition are described in this paper. The 1,2-ethanediolato complexes
can be decomposed to nano-sized BaSn1−x
/Ge
x
O3 preceramic powders. Samples with x = 0.05 consist of only a Ba(Sn,Ge)O3 phase, whereas powders with x = 0.15 and 0.25 show diffraction patterns of both the Ba(Sn,Ge)O3 and BaGeO3 phase. The sintering behaviour was investigated on powders with a BaGeO3 content of 5 and 15 mol%. These powders show a specific surface area of 15.4–15.9 m2/g and were obtained from calcination above 800 °C. The addition of BaGeO3 reduced the sintering temperature of the ceramics drastically. BaSn0.95Ge0.05O3 ceramics with a relative density of at least 90% can be obtained by sintering at 1150 °C for 1 h. The ceramic bodies reveal
a fine microstructure with cubical-shaped grains between 0.25 and 0.6 μm. For dense ceramics, the sintering temperature could
be reduced down to 1090 °C, when the soaking time was extended up to 10 h. 相似文献
14.
Changrong Zhou Xinyu Liu Weizhou Li Changlai Yuan 《Journal of Materials Science: Materials in Electronics》2010,21(4):364-367
Perovskite lead-free piezoelectric ceramics Bi0.5Na0.5TiO3, modified with yttrium and manganese to form a new compound, (1 − x) Bi0.5Na0.5TiO3–xYMnO3 (BNT-YM100x) with x = 0–1.2 mol%, was synthesized by a conventional solid-state reaction method. The effect of YMnO3 on crystal structure, dielectric and piezoelectric properties was investigated. X-ray diffraction analysis shows that the
materials have a single phase perovskite structure with rhombohedral symmetry. Addition of small amount of YMnO3 improves piezoelectric properties and the optimal piezoelectric properties of d
33 = 115 pC/N, k
p = 0.207 and Q
m = 260 were obtained at 0.9% YMnO3 addition. The loss tangent tanδ is approximately constant while Curie temperature decreases with increasing YMnO3 concentration. 相似文献
15.
L. C. Ting H. H. Hsieh H. H. Kang D. C. Ling H. L. Liu W. F. Pong F. Z. Chien P. H. Hor 《Journal of Superconductivity and Novel Magnetism》2007,20(3):249-253
Superconducting transition temperature (T
c) as a function of oxygen concentration for hexagonal rubidium tungsten bronzes Rb
x
WO
y
with 2.80 ≤ y ≤ 3.07 and x = 0.19, 0.23, and 0.27 has been systematically investigated. Three regions corresponding to T
c < 2 K (denoted as superconductivity suppressed region), T
c∼ 3 K (superconductivity uniform region) and T
c > 3 K (superconductivity enhanced region) were identified in T
c–y phase diagram for Rb0.19WO
y
and Rb0.23WO
y
. No superconductivity enhanced region was observed for Rb0.27WO
y
. The superconductivity suppressed region shifts toward higher oxygen content as rubidium concentration increases. The local
ordering of the intercalated rubidium atoms might be responsible for the intriguing T
c–y phase diagram of Rb
x
WO
y
. 相似文献
16.
S. Karimi I. M. Reaney Y. Han J. Pokorny I. Sterianou 《Journal of Materials Science》2009,44(19):5102-5112
Bi(1−x)RE
x
FeO3 (BREF100x, RE = La, Nd, Sm, Gd) has been investigated with a view to establish a broad overview of their crystal chemistry
and domain structure. For x ≤ 0.1, the perovskite phase in all compositions could be indexed according to the rhombohedral, R3c cell of BiFeO3. For Nd and Sm doped compositions with 0.1 < x ≤ 0.2 and x = 0.15, respectively, a new antipolar phase was stabilised similar in structure to PbZrO3. The orthoferrite, Pnma structure was present for x > 0.1, x > 0.15, and x > 0.2 in Gd, Sm, and Nd doped BiFeO3, respectively. For x > 0.2, La doped compositions became pseudocubic at room temperatures but high angle XRD peaks were broad and asymmetric.
These compositions have been indexed as the orthoferrite structure. It was concluded therefore that the orthoferrite phase
appeared at lower values of x as the RE ferrite, end member tolerance factor decreased. However, the compositional window over which the PbZrO3-like phase was stable increased with increasing end member tolerance factor but was not found as single phase in La doped
compositions at room temperature. On heating, the PbZrO3-like phase in BNF20 transformed to the orthoferrite, Pnma structure. T
C for all compositions decreased with decreasing A-site, average ionic polarizabilty and tolerance factor. For compositions
with R3c symmetry, superstructure and orientational, and translational (antiphase) domains were observed in a manner typical
of an antiphase-tilted, ferroelectric perovskite. For the new PbZrO3-like phase orientational domains were observed. 相似文献
17.
We prepared various (Ru0.5Cu0.5)(Sr1.67−x
Ba
x
Nd0.33)(Nd1.34Ce0.66)Cu2O
z
samples with varying Ba contents by x=0, 0.1, 0.2, 0.33, 0.5 and 0.835. X-ray diffraction revealed that the phase purity of the samples increases as the Ba-doping
content increases and single- phase compounds could be obtained for samples with 0.1≤x≤0.33. Contrary to the Ba-free sample, superconductivity could be induced by partially substituting Ba for Sr and superconductivity
with onset T
c of about 15 K is observed for the sample with x=0.2. The superconducting behavior of the Ba-doped samples is discussed in conjunction with thermoelectric power measurements. 相似文献
18.
B. B. Straumal B. Baretzky O. A. Kogtenkova A. B. Straumal A. S. Sidorenko 《Journal of Materials Science》2010,45(8):2057-2061
The microstructure of binary Al100−x
–Mg
x
(x = 10, 15, 18 and 25 wt%) alloys after long anneals (600–4000 h) was studied between 210 and 440 °C. The transition from incomplete
to complete wetting of Al/Al grain boundaries (GBs) by the second solid phase Al3Mg2 has been observed. The portion of completely wetted GBs increases with increasing temperature beginning from T
wsmin = 220 °C. Above T
wsmax = 410 °C all Al/Al GBs are completely wetted by the Al3Mg2 phase. 相似文献
19.
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
20.
Lead-free ferroelectric ceramics of (1−x) [0.88Na0.5Bi0.5TiO3-0.12K0.5Bi0.5TiO3]-x KNbO3(x = 0, 0.02, 0.04, and 0.06) were prepared by the conventional ceramic fabrication technique. The crystal structure, dielectric properties and P-E hysteresis loops were investigated. XRD data showed that all compositions could form pure perovskite structure. Temperature dependence of dielectric constant ε r and dissipation factor tanδ measurement between room temperature and 500∘C revealed that the compounds experience phase transitions that from ferroelectric to anti-ferroelectric and anti-ferroelectric to paraelectric in the range of x = 0–0.04. The frequency dependent dielectric constant showed these compounds were relaxor ferroelectric. At low frequency and high temperature, dielectric constant and dissipation factor increased sharply attributed to the superparaelectric clusters after the KNbO3 doped. 相似文献