共查询到20条相似文献,搜索用时 31 毫秒
1.
Hongxia Huang Kelong Huang Suqin Liu Shuxin Zhuang Dongyang Chen 《Journal of Materials Science》2009,44(16):4460-4465
The AB5-type M1Ni3.5Co0.6Mn0.4Al0.5 alloy (where M1 denotes mixed lanthanide) was modified with different additives (ZnO and MnO2), and the effects of metal oxides on the electrochemical properties of the M1Ni3.5Co0.6Mn0.4Al0.5 − x% M (x = 5, 10; M = ZnO, MnO2) alloy were studied. The results showed that the addition of metal oxides had a positive effect on the activation property
of the alloy electrode. With the addition of ZnO, the maximum discharge capacity of the alloy increased from 315 to 334 mAh/g
(x = 5) and 341 mAh/g (x = 10) with good cycle capability (C
30/C
max) (87% for x = 5 and 85% for x = 10), while the maximum discharge capacity remained invariable and the cyclic stability was deteriorated by the addition
of MnO2. Linear polarization (LP), cycle voltammetry (CV), and electrochemical impedance spectroscopy (EIS) measurements were also
performed to investigate the electrochemical kinetics of alloy electrodes. 相似文献
2.
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
3.
Sheng Liu Shuoqing Yan Heng Luo Lingling Yao Zhaowen Hu Shengxiang Huang Lianwen Deng 《Journal of Materials Science》2018,53(2):1014-1023
Multiferroic properties of La-modified four-layered perovskite Bi5?x La x Fe0.5Co0.5Ti3O15 (0 ≤ x ≤ 1) ceramics were investigated, by analyzing the magnetodielectric effect, magneto-polarization response and magnetoelectric conversion. X-ray diffraction indicated the formation of pure Aurivillius ceramics, and Raman spectroscopy revealed the Bi ions displacement and the crystal structure variation. The enhancement of ferromagnetic and ferroelectric properties was observed in Bi5?x La x Fe0.5Co0.5Ti3O15 after La modification. The evidence for enhanced ME coupling was determined by magnetic field-induced marked variations in the dielectric constant and polarization. A maximum ME coefficient of 1.15 mV/cm·Oe was achieved in Bi4.25La0.75Fe0.5Co0.5Ti3O15 ceramic, which provides the possible promise for novel magnetoelectric device application. 相似文献
4.
S. A. Lokare R. S. Devan D. R. Patil Y. D. Kolekar K. K. Patankar B. K. Chougule 《Journal of Materials Science》2007,42(24):10250-10253
Polycrystalline samples of mixed composites of Ni0.93Co0.02Mn0.05Fe2O4 + BaTiO3 were prepared by conventional double sintering ceramic method. The phase analysis was carried out by using X-ray diffraction
technique. Variation of dc resistivity and thermo emf was studied as a function of temperature. AC conductivity (σac) was investigated in the frequency range 100 Hz–1 MHz. The loss tangent (tan δ) measurements conclude that the conduction
mechanism in these samples is due to small polaron hopping. The magnetoelectric conversion factor, i.e. dc(ME)
H
was studied as a function of intensity of magnetic field and the maximum value 407 μV/cm/Oe was observed at a field of 0.8 kOe
in a composite with 85% BaTiO3 and 15% Ni0.93Co0.02Mn0.05Fe2O4 phase. 相似文献
5.
xBaTiO3 + (1 − x)Ni0.93Co0.02Cu0.05Fe2O4 (x = 0.5, 0.6, 0.7, 0.8) composites with ferroelectric–ferromagnetic characteristics were synthesized by the ceramic sintering
technique. The presence of constituent phases in the composites was confirmed by X-ray diffraction studies. The average grain
size was calculated by using a scanning electron micrograph. The dielectric characteristics were studied in the 100 kHz to
15 MHz. The dielectric constant changed higher with ferroelectric content increasing; and it was constant in this frequency
range. The relation of dielectric constant with temperature was researched at 1, 10, 100 kHz. The Curie temperature would
be higher with frequency increasing. The hysteresis behavior was studied to understand the magnetic properties such as saturation
magnetization (M
s). The composites were a typical soft magnetic character with low coercive force. Both the ferroelectric and ferromagnetic
phases preserve their basic properties in the bulk composite, thus these composites are good candidates as magnetoelectric
materials. 相似文献
6.
The substituted nonstoichiometric perovskite Pr1−x
Ca
x
MnO3−y
compounds have been synthesized by a standard combustion technique, which show uniphase solid solutions. The all samples
of the Pr1−x
Ca
x
MnO3−y
system show an orthorhombic crystal system and the cell volumes are decreased with increasing the larger amounts of substituted
atoms or the increasing x values. The mixed valence of Mn ions is identified by the XAS (XANES/EXAFS) spectroscopy and the amounts of Mn4+ ions are determined by an iodometric titration method. Nonstoichiometric chemical formulas of the Pr1−x
Ca
x
Mn1−τ3+Mnτ4+O3−y
compounds have been obviously formulated. Magnetic properties are investigated by SQUID and thus the Pr1−x
Ca
x
MnO3−y
(x = 0.4, 0.6, and 0.8) compounds show the transition from antiferromagnetic state to paramagnetic state. The Pr1−x
Ca
x
MnO3−y
(x = 0.0, 0.2, and 1.0) compounds show the transition from ferromagnetic state to paramagnetic state. The facts that Mn4+ contents play important roles in the magnetic ordering have been found out. The transport properties have been studied by
the DC electrical conductivity measurement under magnetic fields of 0 G and 3 kG. Maximum and minimum MR ratios are 1016%
of the Pr0.6Ca0.4MnO2.846, and −77.5% of the PrMnO3.021 compound, respectively. 相似文献
7.
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
8.
Sv. Ivanova E. Zhecheva D. Nihtianova R. Stoyanova 《Journal of Materials Science》2011,46(22):7098-7105
XRD-pure Li4Mn5O12 spinels are obtained below 600 °C from oxalate and acetate precursors. The morphology consists of nanometric particles (about
25 nm) with a narrow particle size distribution. HRTEM and electron paramagnetic resonance (EPR) spectroscopy of Mn4+ are employed for local structure analysis. The HRTEM images recorded on nano-domains in Li4Mn5O12 reveal its complex structure. HRTEM shows one-dimensional structure images, which are compatible with the (111) plane of
the cubic spinel structure and the (001) plane of monoclinic Li2MnO3. For Li4Mn5O12 compositions annealed between 400 and 800 °C, EPR spectroscopy shows the appearance of two types of Mn4+ ions having different metal environments: (i) Mn4+ ions surrounded by Li+ and Mn4+ and (ii) Mn4+ ions in Mn4+-rich environment. The composition of the Li+, Mn4+-shell around Mn4+ mimics the local environment of Mn4+ in monoclinic Li2MnO3, while the Mn4+-rich environment is related with that of the spinel phase. The structure of XRD-pure Li4Mn5O12 comprises nano-domains with a Li2MnO3-like and a Li4/3−x
Mn5/3+x
O4 composition rather than a single spinel phase with Li in tetrahedral and Li1/3Mn5/3 in octahedral spinel sites. The annealing of Li4Mn5O12 at temperature higher than 600 °C leads to its decomposition into monoclinic Li2MnO3 and spinel Li4/3−x
Mn5/3+x
O4. 相似文献
9.
Hideki Taguchi Sho Matsuoka Masaki Kato Ken Hirota 《Journal of Materials Science》2009,44(21):5732-5736
Perovskite-type (La1−x
Nd
x
)CoO3 was synthesized using citric acid at 700 °C. The Rietveld method indicated that the crystal structure changed from a rhombohedral
to an orthorhombic system at x = 0.4. The Co–O distance of the rhombohedral structure connected continuously with the average Co–O(2) distance of the orthorhombic
structure, and the Co–O–Co angle of the rhombohedral structure and the Co–O(2)–Co angle of the orthorhombic structure were
continuous. The average particle size of the samples was approximately 55 nm. CH4 oxidation started above 300 °C, and the temperature corresponding to the 50% conversion (T
1/2) of CH4 increased linearly with increases in x. It is considered that the amount of adsorbed oxygen decreased in response to the steric hindrance, and that T
1/2 increased as a result. 相似文献
10.
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
11.
N. H. Mohammed A. I. Abou-Aly I. H. Ibrahim R. Awad M. Rekaby 《Journal of Superconductivity and Novel Magnetism》2011,24(5):1463-1472
In this study, superconducting samples of type Cu0.5Tl0.5Ba2Ca2Cu3O10−δ
,(Cu0.5Tl0.5)-1223, added by SnO2 and In2O3 in nano-scale were prepared by a solid-state reaction technique. The concentrations of both SnO2 and In2O3 were varied from 0.0 to 1.0 wt.% of the total sample’s mass. The prepared samples were characterized using X-ray powder diffraction
(XRD) and scanning electron microscopy (SEM) for phase analysis and microstructure examination, respectively. The electrical
resistivity of the prepared samples was measured by the conventional four-probe technique from room temperature down to the
zero superconducting transition temperature (T
c0). An increase in T
c is observed up to x=0.6 wt.% for (SnO2)
x
Cu0.5Tl0.5Ba2Ca2Cu3O10−δ
, followed by a systematic decrease with increasing nano-SnO2 addition for x>0.6 wt.%. While, for (In2O3)
x
Cu0.5Tl0.5Ba2Ca2Cu3O10−δ
the T
c is slightly changed with x. Room temperature Vickers microhardness measurements were carried out at different applied loads (0.49–2.94 N) for the study
of the mechanical performance of the prepared samples and examination of the effect of different nano-oxides addition on the
microhardness of (Cu0.5Tl0.5)-1223 phase. Furthermore, the true microhardness values (H
o), for both additions, were evaluated through different models and their results were compared with those estimated from the
experimental results in the plateau region. Also, some important mechanical parameters, such as Young’s modulus (E), yield strength (Y), fracture toughness (K) and brittleness index (B), were calculated for both additions. The results clarified that these parameters are strongly dependent on both the applied
loads and the nano-oxides addition. 相似文献
12.
Fang Liu Xin Zhang Kang-Wei Zhu Yu Song Zhen-Hua Shi Bo-Xue Feng 《Journal of Materials Science》2009,44(22):6028-6034
The electrochromic (EC) NiO
x
H
y
films were fabricated through a facile sol–gel method. The formation of high quality NiO
x
H
y
films came from adding the xerogel back into the sol and prolonging the annealing time at gradually increasing temperature
up to 250 °C. Scanning electron microscopy and atomic force microscopy characterizations indicated films were compact, homogenous,
and smooth. Glance angle X-ray diffraction investigation testified NiO
x
H
y
films were of poor crystallization. The Fourier transform infrared, and thermogravimetry and differential thermal analysis
showed that films contained the mixture of NiO, Ni(OH)2, NiOOH, water, and organic substance. With the increasing of the xerogel ratio, the optical absorbance and reflectance of
films had larger differences between the colored and bleached state, respectively. The film with the xerogel ratio of 1:5
showed excellent EC properties with a transmittance contrast as high as 60.88% at λ = 560 nm, which was higher than other
sol–gel nickel oxide films reported. 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.
LiSn2P3 − y
V
y
O12 powders with y = 0.2, 0.4, 0.6, and 0.8 are prepared by mechanochemical milling method. The pellets of the compounds are heat treated at
temperatures between 700 to 1,000 °C for sintering period of 8 h. X-ray diffraction analysis indicates that all samples consist
of rhombohedral crystalline LiSn2P3O12 phase. Energy dispersive X-ray analysis confirmed that V5+ has been successfully substituted into LiSn2P3O12 crystalline phase. The conductivities of the pellets are determined using impedance spectroscopy. Impedance analysis shows
enhancement in both bulk and grain boundary conductivities with increase in y. The enhancement in bulk conductivity is due to decrease in bulk activation energy reflecting an increase in ion mobility
as a result of an increase in bottleneck size. Enhancement in grain boundary conductivity is attributed to increase in the
number of conducting pathways due to an increase in crystallite homogeneity. 相似文献
15.
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
16.
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
17.
The magnetic, thermal, and transport properties of martensitic phase transformation in single crystal Co5Ni2Ga3 have been investigated. The single crystal Co5Ni2Ga3 shows martensitic transformation at 251 K on cooling and 254 K on warming. Large jumps in the temperature-dependent resistance
curve, temperature-dependent magnetization curve, and temperature-dependent thermal conductivity curve are observed at martensitic
transformation temperature (T
M). Negative magnetoresistance due to spin disorder scattering was observed in Co5Ni2Ga3 single crystal at all temperature range. The temperature-dependent negative magnetoresistance shows a peak at T
M, which indicates that the spin disorder increases in the process of phase transition. Co5Ni2Ga3 sample exhibits a temperature dependence of thermal conductivity κ(T) (dκ/dT > 0) due to electrons being above temperature 100 K. 相似文献
18.
Josef Jirák Ladislav Koudelka Jaroslav Pospíšil Petr Mošner Lionel Montagne Laurent Delevoye 《Journal of Materials Science》2007,42(20):8592-8598
Glasses of the ternary system ZnO–Bi2O3–P2O5 were prepared and studied in two compositional series 50ZnO–xBi2O3–(50 − x)P2O5 and (50 − y)ZnO–yBi2O3–50P2O5. Two distinct glass-forming regions were found in the 50ZnO–xBi2O3–(50 − x)P2O5 glass series with x = 0–10 and 20–35 mol.% Bi2O3. All prepared Bi2O3-containing glasses reveal a high chemical durability. Small additions of Bi2O3 (∼5 mol.%) improve thermal stability of glasses. All glasses crystallize on heating within the temperature range of 505–583 °C.
Structural studies by Raman and 31P MAS NMR spectroscopies showed the rapid depolymerisation of phosphate chains within the first region with x = 0–15 and the presence of isolated Q0 phosphate units within the second region with x = 20–35. Raman studies showed that bismuth is incorporated in the glass structure in BiO6 units and their vibrational bands were observed within the spectral region of 350–700 cm−1. The evolution of properties and the spectroscopic data are both in accordance with a network former effect of Bi2O3. 相似文献
19.
Quasi-one-dimensional TiO2-based nanostructures have been produced through hydrothermal treatment-without additives and in the presence of chitosan—of anatase nanopowder synthesized by an electrochemical sol-gel process. The morphology, phase composition, and structure of the hydrothermal synthesis products were studied by various physicochemical characterization techniques, including high-resolution electron microscopy, X-ray diffraction, and IR spectroscopy. The results demonstrate that the forming one-dimensional structures are isostructural with β-titanic acid, H2Ti3O7. Heat treatment at t ≥ 500°C yields a mixture of sodium polytitanates, Na y Ti x O2x + 1, with y = 0.5–2 and x = 2–5. The surface morphology and shape of the nanostructures persist up to 700°C. The key features of the formation of quasi-one-dimensional TiO2-based structures in the presence of chitosan have been identified. 相似文献
20.
Yingfang Zhu Jingwei You Haifu Huang Guangxu Li Wenzheng Zhou Jin Guo 《材料科学前沿(英文版)》2017,11(2):155-161
A layered oxide Li[Ni1/3Mn1/3Co1/3]O2 was synthesized by an oxalate co-precipitation method. The morphology, structural and composition of the as-papered samples synthesized at different calcination temperatures were investigated. The results indicate that calcination temperature of the sample at 850°C can improve the integrity of structural significantly. The effect of calcination temperature varying from 750°C to 950°C on the electrochemical performance of Li[Ni1/3Mn1/3Co1/3]O2, cathode material of lithiumion batteries, has been investigated. The results show that Li[Ni1/3Mn1/3Co1/3]O2 calcined at 850°C possesses a higher capacity retention and better rate capability than other samples. The reversible capacity is up to 178.6 mA?h?g-1, and the discharge capacity still remains 176.3 mA?h?g-1 after 30 cycles. Moreover, our strategy provides a simple and highly versatile route in fabricating cathode materials for lithium-ion batteries. 相似文献