共查询到20条相似文献,搜索用时 31 毫秒
1.
Min Xu Feifei Wang Tao Wang Xinman Chen Yanxue Tang Wangzhou Shi 《Journal of Materials Science》2011,46(13):4675-4682
In this study, the phase diagram and electric properties were demonstrated for a (Mn, K)-modified Bi0.5Na0.5TiO3 (BNT)-based solid solution. (0.935−x) Bi0.5Na0.5TiO3−xBi0.5K0.5TiO3−0.065BaTiO3 with 0.5% mol Mn doping was prepared by a conventional solid-state reaction method. A morphotropic phase boundary (MPB) formed
between the ferroelectric rhombohedral and tetragonal phases around x of 0.04 with the MPB tolerance factor t of 0.984–0.986. The temperature and composition dependence of the dielectric, piezoelectric, ferroelectric properties along
with the strain characteristics were investigated in detail and a phase diagram was presented. Around the MPB region, the
maximum values of piezoelectric constant d33* d_{33}^{*} of 290 pC/N, d
33 of 155 pC/N, dielectric constant e33T /e0 \varepsilon_{33}^{T} /\varepsilon_{0} of 1059 and low dielectric loss tangent tan δ of 0.017 were obtained. In addition, the authors also suggest that the solid
solution with composition x of 0.24, exhibiting both high-depolarization temperature T
d of 182 °C, d33* d_{33}^{*} of 156 pC/N, d
33 of 130 pC/N, will be favorable for high-temperature actuator and sensor applications. 相似文献
2.
Satyendra V. Vikram D. M. Phase Vishal S. Chandel 《Journal of Materials Science: Materials in Electronics》2010,21(9):902-905
Solid-state reaction synthesised K2Ti6O13 lead-free ceramic was characterized using XRD, SEM, and X-band EPR, at room temperature. EPR-spectra showed the presence
of
( \textFe\textTi¢ - V\textO ·· ) \left( {{\text{Fe}}_{\text{Ti}}^{\prime } - V_{\text{O}}^{ \bullet \bullet } } \right) defect associate dipoles, in orthorhombic phase, responsible for the broadening of the dielectric anomaly identified in the
ε
r (T) plots at T
C
~ 300 °C. This anomaly resembled a ferroelectric–paraelectric type phase transition following Curie–Weiss type trend. Besides,
dielectric loss mechanism jointly represented electrical conduction, dipole orientation, and space charge polarization. 相似文献
3.
I. A. Dankov K. V. Novichkov E. F. Tokarev S. A. Sakharov O. A. Buzanov 《Measurement Techniques》2010,53(2):134-137
Measurements of the temperature variations in the relative dielectric constants e33T/e0 \varepsilon_{33}^T/{\varepsilon_0} , e11T/e0 \varepsilon_{11}^T/{\varepsilon_0} ,and e22T/e0 \varepsilon_{22}^T/\varepsilon {}_0 , conductivities g11, g22, and g33, elastic constants C11D C_{11}^D , C66D C_{66}^D , and S22E S_{22}^E , and electromechanical coupling constants kt, k26, and k12 of lanthanum-gallium tantalate over temperatures of 20–600°C are reported. Data are presented on the effect of lifetime (breakdown)
testing on these characteristics of the piezoelectric crystals after retention at a temperature of 625°C for 250 h. 相似文献
4.
The microstructure of the eutectic alloy Fe30Ni20Mn35Al15 (in at.%) was modified by cooling at different rates from 1623 K, i.e., above the eutectic temperature. The lamellar spacing
decreased with increasing cooling rate, and in water-quenched specimens lamellae widths of ~100 nm were obtained. The orientation
relationship between the fcc and B2 lamellae was found to be sensitive to the cooling rate. In a drop-cast alloy the Kurdjumov–Sachs
orientation relationship dominated, whereas the orientation relationship in an arc-melted alloy with a faster cooling rate
was
\textfcc( [`1]12 )//\textB2( 0 1 1 ); \textfcc[ 1[`1]1 ]//\textB2 [ 1[`1]1 ] \textand \textfcc( 0[`1]1 )//\textB2( 00 1 );\text fcc[ 0 1 1 ]//\textB2[ [`1][`1]0 ] {\text{fcc}}\left( {\bar{1}12} \right)//{\text{B2}}\left( {0 1 1} \right);\;{\text{fcc}}\left[ {1\bar{1}1} \right]//{\text{B2 }}\left[ {1\bar{1}1} \right] \,{\text{and}}\,{\text{fcc}}\left( {0\bar{1}1} \right)//{\text{B2}}\left( {00 1} \right);{\text{ fcc}}\left[ {0 1 1} \right]//{\text{B2}}\left[ {\bar{1}\bar{1}0} \right] . The hardness increased with microstructural refinement, obeying a Hall–Petch-type relationship. The strength of the alloy
decreased significantly above 600 K due to softening of the B2 phase. 相似文献
5.
E. Yousef A. El-Adawy M. H. Makled A. E. Al-Salami 《Journal of Materials Science》2010,45(11):2930-2937
The crystallization kinetics of the TeO2/TiO2/As2O3 glassy system was studied under nonisothermal conditions. The method was applied to the experimental data obtained by differential
thermal analysis (DTA), using continuous-heating techniques. In addition, two approaches were used to analyze the dependence
of glass transition temperature (T
g) on the heating rate (β): One is the empirical linear relationship between (T
g) and (β); The other approach is the use of straight line from the plot of
ln( T\textg2 /b ) \textvs . 1/T\textg \ln \left( {T_{\text{g}}^{2} /\beta } \right)\,{\text{vs}} .\,1/T_{\text{g}} for evaluation of the activation energy for glass transition. The crystallization results are analyzed, and both the activation
energy of crystallization process and the crystallization mechanism are characterized. 相似文献
6.
Aline Bruna da Silva Celio Wisniewski Jo?o Victor Almeida Esteves Rinaldo Gregorio 《Journal of Materials Science》2010,45(15):4206-4215
Poly(vinylidene fluoride), PVDF, samples containing exclusively the polar β phase were obtained by crystallization from N,N-dimethylformamide (DMF) solution at 60 °C and subsequent pressing. Some of these samples were uniaxially drawn at 120 °C
at draw ratio of 4, resulting in oriented films. Oriented and unoriented samples were characterized as to relative fraction
of β phase, degree of crystallinity and orientation by infrared spectroscopy (FTIR), differential scanning calorimetry (DSC),
and wide-angle X-ray diffraction (WAXD). The dependence on frequency of the real (
e\textr¢ \varepsilon_{\text{r}}^{\prime} ) and imaginary (
e\textr¢¢ \varepsilon_{\text{r}}^{\prime\prime} ) components of the relative permittivity of the samples was determined between 104 and 1.7 × 107 Hz. The coercive field and stable and metastable remanent ferroelectric polarization were determined from the hysteresis
loop obtained by the ramp voltage technique, described in detail in this work. The results allowed verification of the effect
of drawing on structure and of the resulting structure on the dielectric properties, remanent polarization, and coercive field
of β-PVDF. A possible effect of the crystal–amorphous interphase region on the metastable remanent polarization is suggested.
The results obtained with the oriented and unoriented samples were compared with those obtained for films commercialized by
Piezotech S.A. 相似文献
7.
Anwar Ali Rajan Patel Shahjahan Nizamul Haque Ansari 《International Journal of Thermophysics》2010,31(3):572-584
The apparent molar volumes ([`(V2)]){(\overline{V_2})} for glycine (Gly), l-alanine (Ala), phenylalanine (Phe), and glycylglycine (Gly-Gly) in 0.10 m aqueous d-galactose solutions have been determined from density measurements at (298.15, 303.15, 308.15, and 313.15) K. The data for
([`(V2)]){(\overline{V_2})} were utilized to estimate the partial molar volume at infinite dilution ([`(V20)]){(\overline{V_2^0})} , and experimental slope (Sv*){(S_{\rm v}^\ast)} . The transfer volume, ([`(V20)](tr)){(\overline{V_{2}^0}_{\rm (tr)})} , and hydration number, (n
H) were also evaluated. The viscosity data were used to evaluate A- and B-coefficients of the Jones–Dole equation, the free energy of activation of viscous flow per mole of the solvent (Dm10* ){\left(\Delta \mu_{1}^{0\ast} \right)} and the solute (Dm20* ){\left(\Delta \mu _{2}^{0\ast} \right)} . The molar refractivity (R
D) was calculated from refractive index data. The results were discussed in terms of hydrophilic–ionic, hydrophilic–hydrophobic,
and hydrophobic–hydrophobic interactions, and structure-making/-breaking ability of the solute (AAs/peptide) in aqueous d-galactose solutions. 相似文献
8.
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
9.
V. V. Bannikov I. R. Shein A. L. Ivanovskii 《Journal of Superconductivity and Novel Magnetism》2011,24(5):1693-1696
Using the ab initio FLAPW-GGA method, we examine the electronic and magnetic properties of nitrogen-doped non-magnetic sesquioxide La2O3 emphasizing the role of doping sites in the occurrence of d
0-magnetism. We predict the magnetization of La2O3 induced by nitrogen impurity in both octahedral and tetrahedral sites of the oxygen sublattice. The most interesting results
are that (i) the total magnetic moments (about 1 μ
B per supercells) are independent of the doping site, whereas (ii) the electronic spectra of these systems differ drastically:
La2O3:N with six-fold coordinated nitrogen behaves as a narrow-band-gap magnetic semiconductor, whereas with four-fold coordinated
nitrogen is predicted to be a magnetic half-metal. This effect is explained taking into account the differences in N-2pzˉ -2p_{z}^{\downarrow \uparrow}
versus N-2px,yˉ -2p_{x,y}^{\downarrow \uparrow} orbital splitting for various doping sites. Thus, the type of the doping site is one of the essential factors for designing
of new d
0-magnetic materials with promising properties. 相似文献
10.
Feifei Wang Min Xu Tao Wang Yanxue Tang Wangzhou Shi 《Journal of Materials Science》2012,47(5):2352-2358
Phase transition and electrical properties were demonstrated for a Li-modified Bi0.5Na0.5TiO3-based solid solution. (0.935 − x)Bi0.5Na0.5TiO3 − xBi0.5Li0.5TiO3 − 0.065BaTiO3 with 0.5 mol% Mn doping was prepared by a conventional solid state reaction method. Close inspection of X-ray diffraction
patterns indicated that no characteristic peaks splitting happened, indicating the pseudocubic structure for all the compositions.
At a critical composition x of 0.06, optimized performance was obtained with piezoelectric constant d
33 of 176 pC/N, electromechanical coupling factors k
P of 0.33, and k
t of 0.52, respectively. In addition, it was found that the Li substitution could lead to a disruption of long-range ferroelectric
order and obtain enhanced frequency dispersion behavior accompanied with the decreasing of the depolarization temperature
T
d, which was responsible for the observed weaker ferroelectric polarization and electromechanical response. The composition
induced structure evolution was also discussed combined with the Raman spectroscopy. 相似文献
11.
B MUNIRATHINAM M KRISHNAIAH M MANIVEL RAJA S ARUMUGAM K PORSEZIAN 《Bulletin of Materials Science》2011,34(1):121-124
In this paper we report the investigation of transition metal oxide compound, La0·67Ca0·25Sr0·04Ba0·04MnO3 (LCSBMO), along with La0·67Ca0·33MnO3 (LCMO), synthesized by sol–gel route under identical conditions. The effect of simultaneous low level substitution of large
size ions such as Sr2+ and Ba2 + for Ca2 + ions on the electronic transport and magnetic susceptibility properties are analysed and compared apart from microstructure
and lattice parameters. The temperature dependent electrical transport of the polycrystalline pellets of LCSBMO and LCMO when
obeying the well studied law, r = r0 + r2 T2\rho = \rho_{0} + \rho_{2} \;T^{2} for T < T
MI
, is observed to differ by more than 50% from the values of ρ
0 and ρ
2, with the former compound showing enhanced electrical conductivity than the latter. Similarly in fitting the adiabatic small
polaron model for resistivity data of both the samples for T > T
MI
, the polaron activation energy is found to differ by about 11%. In addition, the temperature dependent a.c. magnetic susceptibility
study of the compounds shows a shift of about 6% in the paramagnetic to ferromagnetic transition temperature (285 K for LCSBMO
and 270 K for LCMO). 相似文献
12.
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
13.
S. M. Rao J. K. Srivastava M. K. Wu B. H. Mok C. L. Chen M. C. Ling H.-L. Liu Y. Y. Chen J. C. Ho 《Journal of Superconductivity and Novel Magnetism》2011,24(4):1249-1262
We report here SQUID (magnetization) measurements, along with supporting specific heat, Raman, SEM (scanning electron microscope),
EDX (energy dispersive X-ray) and XRD (X-ray diffraction) measurements, on Cu-doped and undoped double perovskite Sr22+Y3+Ru5+O62-\mathrm{Sr}_{2}^{2+}\mathrm{Y}^{3+}\mathrm{Ru}^{5+}\mathrm{O}_{6}^{2-} (abbreviated as SrY2116) system grown as single crystal using high-temperature solution growth technique. These measurements
show the undoped system to be a nonmetallic (insulating) spin glass (SG) and the ∼5–30% Cu-doped (i.e. Cu-concentration/(Cu + Ru-concentration)
∼5–30%) system to be a spin glass superconductor (SGSC) with T
c (critical temperature) ∼28–31 K and superconducting volume fraction, f
sc∼2.2–9%. To mention, similar measurements done on undoped and Cu-doped BaY2116 and BaPr2116 systems show for them the same
(SG, SGSC) behaviors. However they show a decrease in T
c and f
sc when diamagnetic Y3+ ions are replaced by Pr3+ spins, presumably due to enhanced internal pair breaking, and also decreased Cu–O–Cu overlap, owing to Pr3+ presence; these phenomena are known to exist in the Pr123 compound, PrBa2Cu3O7−δ
(δ∼0), due to ∼10% of Pr3+ ions having tendency to occupy Ba2+ sites. Measurements done on undoped and Cu-doped SrHo2116 show similar SG and SGSC properties. Further, the undoped and Cu-doped
SrY2116 crystals grown by hydrothermal growth technique (i.e., grown using lower temperature and high pressure) show same
behaviors. From these investigations it can be said that the undoped Ru-double perovskites (A2BB′O6, B′=Ru) are SG systems and that Cu-doped Ru-double perovskites (A2BB′O
δ
, δ∼6, B′=Ru1−x
Cu
x
, 0<x≲0.3) are SG superconductors (SGSCs). Results are discussed. 相似文献
14.
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
15.
B. Samantaray S. K. Srivastava S. Ravi I. Dhiman A. Das 《Journal of Superconductivity and Novel Magnetism》2011,24(6):1933-1937
La0.85Ag0.15MnO3, the colossal magnetoresistance compound was prepared and the neutron powder diffraction patterns at different temperatures
down to 19 K were recorded to study their crystal structure and magnetic properties. These patterns were analyzed by the Rietveld
refinement technique and are found to be free from any impurity phase. The compound is found to crystallize in a mixture of
R[`3]cR\overline{3}c and Pnma space group and the phase fraction is found to vary with temperature. A cross-over from R[`3]cR\overline{3}c dominated high temperature phase to Pnma dominated low temperature phase at around 130 K was observed. At low temperatures, especially below 285 K, the diffraction
patterns could be refined by including the magnetic reflections corresponding to ferromagnetic structure. The refined magnetic
moment of Mn ions is found to be along b axis of the unit cell with a maximum moment of 3.74 μB at 19 K and this value is comparable to the saturation magnetization observed at 20 K from magnetization measurement. 相似文献
16.
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
17.
The temperature dependence of the critical resolved shear stress (CRSS), τ, of ultra-pure tantalum single crystals (RRR ≥ 14000) observed below 250 K for a range of shear-strain rates
[(g)\dot] = 2×10 - 5 - 6×10 - 3 \texts - 1 \dot{\gamma } = 2\times 10^{ - 5} - 6\times 10^{ - 3} \,{\text{s}}^{ - 1} was analyzed within the framework of a kink-pair nucleation model of flow stress. The CRSS/strain-rate data follow the model
formulation t 1/ 2 = C + D ln[(g)\dot] \tau^{ 1/ 2} = C + D\,{ \ln }\dot{\gamma } , where C and D are positive constants, for each deformation temperature T in the range 78–250 K. Evaluation of the various slip-parameters of flow stress points to (211)[[`1]11] [\bar{1}11] slip system responsible for the yielding of ultra-pure tantalum single crystals in the so-called stress/temperature regime
III (T < 250 K). The value of the pre-exponential factor
[(g)\dot]\texto \dot{\gamma }_{\text{o}} in the Arrhenius-type equation for the shear-strain rate [(g)\dot] \dot{\gamma } is found to be of the order of 105 s−1, which is substantially lower than that
( [(g)\dot]\texto ~ 107 \texts - 1 ) \left( {\dot{\gamma }_{\text{o}} \sim 10^{7} \,{\text{s}}^{ - 1} } \right) determined in the stress/temperature regime II (250–400 K) and contradicts the assumption invariably made in most of the
theoretical models of flow stress that
[(g)\dot]\texto \dot{\gamma }_{\text{o}} is a constant over a wide temperature range. 相似文献
18.
Zi-de Yu Xiao-ming Chen Han-li Lian Qian Zhang Wen-xin Wu 《Journal of Materials Science: Materials in Electronics》2018,29(22):19043-19051
Pure K0.5Na0.5NbO3 lead-free piezoelectric ceramics without any dopants/additives were sintered at various temperatures (950–1125 °C) in low pO2 atmosphere (pO2?~?10?6 atm). All ceramics exhibit high relative densities (>?94%) and low weight loss (<?0.6%). Compared to the ceramics sintered in air, the ceramics sintered in low pO2 exhibit improved electrical properties. The piezoelectric constant d33 and converse piezoelectric constant d33* are 112 pC/N and 119 pm/V, respectively. The ceramics show typical ferroelectric behavior with the remnant polarization of 21.6 µC/cm2 and coercive field of 15.5 kV/cm under measurement electric field of 70 kV/cm. The good electrical properties of the present samples are related to the suppression of volatility of the alkali cations during the sintering process in low pO2 atmosphere. 相似文献
19.
Qi-Jun Liu Zheng-Tang Liu Qian-Qian Gao Li-Ping Feng Hao Tian 《Journal of Materials Science》2012,47(7):3046-3051
The first-principles density-functional theory has been carried out to study the structural, electronic, and optical properties
of N-doped orthorhombic SrHfO3. The calculated results show the doping of N substituting for O is most favorable. When the doping of N substituting for
Hf(Sr), the impurity energy level of N 2p states is introduced in the forbidden band. When the doping of N substituting for
O1(O2), the width of the valence bands increases due to the presence of N 2p states in the top of valence bands. The doping
of N resulting in red-shift has been studied by analysing the imaginary part of dielectric function e2 (w) \varepsilon_{2} (\omega ) of N-doped orthorhombic SrHfO3. 相似文献
20.
In this study, a constitutive analysis of the flow responses of Ti–6Al–4V under various strain rates [(e)\dot] \dot{\varepsilon } was conducted by separately quantifying the hardening and softening effects of microstructure, interstitial solute and deformation
heating on the total stress. For this purpose, a series of compression tests on an extra-low interstitial grade alloy with
equiaxed, lamellar, or bimodal microstructures was performed at
10 - 3 £ [(e)\dot] £ 10 \texts - 1 10^{ - 3} \le \dot{\varepsilon } \le 10\;{\text{s}}^{ - 1} until the metal fractured, and the results were compared to those of the commercial grade alloy. The thermal stress σ* increased with an increasing interstitial solute concentration; the athermal stress increased in the order of equiaxed, lamellar,
and bimodal microstructures. Load–unload–reload tests revealed that the flow softening at a relatively high [(e)\dot] \dot{\varepsilon } was likely caused by deformation heating rather than by microstructure change; thus flow softening was attributed to a decrease
in σ*. Finally, a mechanical threshold stress model was extended to capture those observations; the modified model can provide
a reasonable prediction of flow stress in Ti–6Al–4V with different microstructures and interstitial solute concentrations. 相似文献