共查询到20条相似文献,搜索用时 15 毫秒
1.
Pickup DM Wetherall KM Knowles JC Smith ME Newport RJ 《Journal of materials science. Materials in medicine》2008,19(4):1661-1668
Glasses from the CaO–TiO2–P2O5 system have potential use in biomedical applications. Here a method for the sol–gel synthesis of the ternary glass (CaO)0.25(TiO2)0.25(P2O5)0.5 has been developed. The structures of the dried gel and heat-treated glass were studied using high-energy X-ray diffraction.
The structure of the binary (TiO2)0.5(P2O5)0.5 sol–gel was studied for comparison. The results reveal that the heat-treated (CaO)0.25(TiO2)0.25(P2O5)0.5 glass has a structure based on chains and rings of PO4 tetrahedra, held together by a combination of electrostatic interaction with Ca2+ ions and by corner-sharing oxygen atoms with TiO6 octahedra. In contrast, the (TiO2)0.5(P2O5)0.5 glass has a structure based on isolated P2O7 units linked together by corner-sharing with TiO6 groups. The results suggest that both the dried gels possess open porous structures. For the (CaO)0.25(TiO2)0.25(P2O5)0.5 sample there is a significant increase in Ca–O coordination number with heat treatment. 相似文献
2.
Guo-Zhong Zang Li-Ben Li Xiu-Jie Yi Juan Du Yan Li 《Journal of Materials Science: Materials in Electronics》2012,23(5):977-980
Lead-free (K0.48Na0.52)(W2/3Bi1/3)xNb1−xO3 (KNN-WBi) piezoceramics with x ranging from 0.004 to 0.010 were synthesized by conventional ceramic processing. The sintered
KNN-WBi ceramics showed perovskite structure without detectable secondary phase containing W and Bi. With increasing x, the
orthorhombic-tetragonal phase transition temperature (T
O-T) decreased from 200 to 184 °C whereas, the tetragonal-cubic phase transition temperature (T
C) decreased slightly. With the doping of (W2/3Bi1/3), the piezoelectric properties were greatly improved and the piezoelectric constants d
33, k
p, Q
m exhibited maximum values of 136 pC/N, 43.3% and 175, respectively at x = 0.008. The KNN-WBi ceramics also exhibited good ferroelectric properties with remnant polarizations P
r higher than 25 μC/cm2 and coercive fields E
c lower than 1,000 V/mm. The results strongly suggest that the B site doping of constructed quinquevalent element is an effective
method for the investigation of potassium sodium niobate system. 相似文献
3.
Copper-cerium-zirconium catalysts loaded on TiO2 prepared by a wet impregnation method were investigated for NH3-selective catalytic reduction (SCR) of NOx. The reaction mechanism was proposed on the basis of results from in situ diffuse reflectance infrared transform spectroscopy (DRIFT). When NH3 is introduced, ammonia bonded to Lewis acid sites is more stable over CuCe0.25Zr0.75/TiO2 at high temperature, while Brønsted acid sites are more important than Lewis acid sites at low temperature. For the NH3+NO+O2 co-adsorption, NH3 species occupy most of activity sites on CuCe0.25Zr0.75/TiO2 catalyst, and mainly exist in the forms of NH4 + (at low temperature) and NH3 coordinated (at high temperature), playing a crucial role in the NH3-SCR process. Two different reaction routes, the L-H mechanism at low temperature (< 200°C) and the E-R mechanism at high temperature (> 200°C), are presented for the SCR reaction over CuCe0.25Zr0.75/TiO2 catalyst. 相似文献
4.
Guidan Wei Aimin Sun Jinyuan Ma Long Zheng Guofeng Yang Xiu’e Zhang 《Journal of Superconductivity and Novel Magnetism》2010,23(2):209-212
A series of samples of (MgB2−x
C
x
)0.97Cu0.03 (x=0.00, 0.05, 0.10, 0.15, 0.20, 0.25) and MgB2 were synthesized by a solid state reaction method. The structure, superconducting transition temperature and transport properties
of the samples were studied by means of X-ray diffraction (XRD) and resistivity measurements. It is found that the c-axis of the lattice remains unchanged with increasing C doping, while the a-axis shows a small decrease. The T
c of the samples steadily decreases with increasing C doping. It is suggested that the chemical pressure effect plays a more
important role influencing the normal state transport and T
c than the change of carrier concentration. 相似文献
5.
Qiang Li Shengxiang Bao Yuanxun Li Lijie Song Wei Jiang Yongda Hu 《Journal of Materials Science: Materials in Electronics》2015,26(11):8887-8891
In this paper, Cr-doped Bi0.9Ba0.1Fe1?xCrxO3 (x = 0.00, 0.05, 0.10, 0.15, 0.20) ceramic materials were prepared by traditional state solid synthesized method, and the effects of Cr3+ ion on magnetic and dielectric properties were investigated. All samples showed BiFeO3 phase formation were successful synthesized. The SEM images showed the shape of samples changed from regular to irregular shape. With increasing of Cr2+ ions, Saturation magnetization (M s) increased from 5.24 to 8.6 emu/g, and then decreased to 7.31 emu/g, and coercivity (H c) increased from 110.66 to 256.49 Oe. All the samples showed high dielectric constants at low frequency and the values of dielectric constants decreased slightly with frequency increasing. Delectric loss (tanδ) values kept a steady in a wide range frequency of 10–600 MHz. They ranged in tanδ from 0.01 to 0.07, which was a low dielectric loss in Bi0.9Ba0.1Fe1?xCrxO3 ceramics. 相似文献
6.
A. S. Saidov Sh. N. Usmonov K. T. Kholikov D. Saparov 《Technical Physics Letters》2007,33(10):853-855
Epitaxial layers of n-type solid solutions of the (Si2)1 ? x (CdS)x system (0 ≤ x ≤ 0.01) were grown by liquid phase epitaxy from a tin-based solution melt confined between two horizontal p-type single crystal silicon substrates. The photosensitivity spectra of p-Si/n-(Si2)1 ? x (CdS)x structures have been measured. A photoresponse peak at E ≈ 2.35 eV (1.25 eV below the top of the valence band of silicon) has been observed, which is probably related to an impurity level due to CdS molecules. 相似文献
7.
The linear thermal expansion coefficient of TlIn1?x CexSe2 (0 ≤ x ≤ 0.04) crystals has been measured at temperatures from 300 to 600 K. 相似文献
8.
Kalengay Mbela T. Moyo Nadir S.E. Osman 《Journal of Materials Science: Materials in Electronics》2016,27(9):8916-8922
Magnesium-iron chromium oxides (Mg0.2Cr1.8?x Fe x O3 with x varying from 0.3 to 0.9) produced by hydrothermal process in a stirred pressure reactor from pure metal chlorides have been annealed at 700 °C. Single phase corundum structure and nanophase structure of the as-synthesized samples were confirmed by X-ray diffraction (XRD). Instead of the correlation between H EB and D XRD observed at T A = 600 °C, we find significant changes. The H EB increases with decreasing particle size reaches a maximum at ~43 nm (x = 0.5) then decreases. 相似文献
9.
Dongyun Gui Hui Zhang Liang Fang Lihui Xue 《Journal of Materials Science: Materials in Electronics》2008,19(6):543-546
High dielectric constant and low loss ceramics in the system Ba4LaTiNb3−x
Ta
x
O15 (x = 0–3) have been prepared by conventional solid-state ceramic route. Ba4LaTiNb3−x
Ta
x
O15 solid solutions adopted A5B4O15 cation-deficient hexagonal perovskite structure for all compositions. The materials were characterized at microwave frequencies.
They show a linear variation of dielectric properties with the value of x. Their dielectric constant varies from 53.1 to 42.3, quality factor Qu × f from 18,790 to 28,070 GHz and temperature variation of resonant frequency from +94.3 to +33.1 ppm/°C as the value of
x increases. 相似文献
10.
T. G. Aminov G. G. Shabunina E. V. Busheva V. M. Novotortsev 《Inorganic Materials》2017,53(2):164-170
The magnetic properties of Co x Zn1–x Cr2S4 solid solutions have been studied at temperatures from 5 to 300 K in static magnetic fields of 7.96 × 103 and 3.58 × 106 A/m. We have determined the Curie temperatures, Curie–Weiss constants, and effective magnetic moments of the solid solutions. The experimental data are discussed with allowance for the magnetic phase diagram of the system. 相似文献
11.
K. P. THUMMER M. P. PANDYA K. H. JANI K. B. MODI H. H. JOSHI 《Journal of Materials Science》2005,40(19):5215-5221
In order to study the effect of co-substitution of Al3 + and Cr3 + for Fe3+ in MgFe2O4 on its structural and magnetic properties, the spinel system MgAl x CrxFe2 ? 2xO4 (x = 0.0–0.8) has been characterized by X-ray diffraction, high field magnetization, low field a.c. susceptibility and 57Fe Mössbauer spectroscopy measurements. Contrary to the earlier reports, about 50% of Al3 + is found to occupy the tetrahedral sites. The system exhibits canted spin structure and a central paramagnetic doublet was found superimposed on the magnetic sextet in the Mössbauer spectra (0.5 > x > 0.2). Thermal variation of a.c. susceptibility exhibits normal ferrimagnetic behaviour. 相似文献
12.
V. V. Martsinkevich V. G. Ponomareva T. N. Drebushchak G. V. Lavrova S. S. Shatskaya 《Inorganic Materials》2010,46(7):765-769
Cs1 − x
Rb
x
H2PO4 solid solutions have been synthesized for the first time in a broad composition range, x = 0.03–0.9. At room temperature, the Cs1 − x
Rb
x
H2PO4 solid solutions are isostructural with the low-temperature phase of CsH2PO4 over the entire composition range studied. In the CsH2PO4-based solid-solution series, the unit-cell parameters and volume decrease with increasing Rb content. At high temperatures,
the Cs1 − x
Rb
x
H2PO4 solid solutions exist in the range x = 0–0.4, are isostructural with cubic CsH2PO4, and have a smaller unit-cell parameter. 相似文献
13.
14.
Cr x Ge1? x (x ~ 0.08) films were grown on GaAs (001) and Ge (001) substrates using molecular beam epitaxy (MBE) method, and their magnetic and transport properties have been studied in the temperature range between 1.8 and 300 K. All of the films exhibited weak paramagnetic behavior. Transport measurements showed that magnetoresistance ratio and the anomalous Hall resistance depend on the Cr concentration x and the kinds of substrate. 相似文献
15.
Qing Yang Yingxin Guo Baoxin Liu Cheng Chen Wenbao Wang Guilin Ma 《Journal of Materials Science》2009,44(8):2031-2037
Doubly doped LaErO3 ceramics, La0.9Ba0.1Er1−x
Mg
x
O3−α (x = 0.05, 0.10, 0.15, 0.20), were synthesized by solid-state reaction method and characterized by X-ray diffraction (XRD).
The samples have a single orthorhombic perovskite-type structure. The conduction behavior was investigated using various electrochemical
methods including AC impedance spectroscopy, gas concentration cell, isotope effect of hydrogen, and hydrogen electrochemical
permeation (pumping) in the temperature range of 500–1000 °C. The results indicated that specimens were pure ionic conductors
under low oxygen partial pressure (about 10−7–10−20 atm) and mixed conductors of proton, oxide ion, and electron hole under high oxygen partial pressure (about 10−5–1 atm). The pure ion conduction of the ceramics in hydrogen atmosphere was confirmed by electromotive force method of hydrogen
concentration cell, and the observed emf values coincided well with the theoretical ones. The conductivity in H2O–Ar atmosphere was higher than that in D2O–Ar atmosphere, exhibiting an obvious isotope effect and proton conduction in water vapor containing atmosphere. It has been
confirmed by electrochemical hydrogen permeation (hydrogen pumping) experiment that the ceramics were mainly proton conductors
in hydrogen containing atmosphere. Whereas in dry oxygen-containing atmosphere, observed emf values of the oxygen concentration
cell were far lower than the theoretical ones, indicating that the ceramics were mixed conductors of electron hole and oxide
ion. 相似文献
16.
JiQiang Jia JianMin Li GaoYang Zhao 《Journal of Superconductivity and Novel Magnetism》2018,31(6):1733-1739
By the combined use of the sol-gel and pulsed laser deposition methods, the SrTiO3/YBa2Cu3O7?x (STO/YBCO) heterostructure was prepared on a LaAlO3 substrate. XRD results and φ scanning test showed that the prepared STO/YBCO heterostructure had good biaxial texture. Moreover, a Pt electrode was sputtered on the STO/YBCO heterostructure to investigate the current density-voltage (J ? V) characteristic curves of STO/YBCO in the 50–300 K temperature range. The results showed that the STO/YBCO heterostructure had good rectifying characteristics. With an applied positive bias voltage smaller than 3.7 V, the current density of the STO/YBCO heterostructure decreased with the decrease of temperature; for higher voltages, on the contrary, the current density increased with the decrease of temperature. When the YBCO experienced superconducting transition, the turn-on voltage (V t) changed suddenly due to the sudden opening of the superconducting energy gap of YBCO. The V t variation obtained from the experiment was essentially consistent with the known value of the YBCO superconducting energy gap. 相似文献
17.
Lipeng Jiang Xiyan Zhang Shiqi Zhu He Tang Qingxi Li Wenmin Zhang Xiaoyun Mi Liping Lu Hongwei Liu Xiuling Liu 《Journal of Materials Science: Materials in Electronics》2018,29(11):9045-9051
Y3?yAl5?xGaxO12:Ce3+y phosphors were prepared by high temperature solid state reaction method. The crystal structures, the influence of Ga3+ concentration on the photoluminescence (PL), cathodoluminescence, thermal stability and morphology of the phosphors were studied in detail. The results indicated that diffraction angle of the samples decreased gradually with the increase of Ga3+ ions content in XRD pattern. The emission peak of the spectra show a progressive blue-shift, the intensity increased first and then decreased and the optimal Ga3+ concentration in Y2.94Al5?xGaxO12:Ce3+0.06 phosphors is x?=?0.75. The critical concentration of Ce3+ in YAGG:Ce3+ phosphors is affected with the ratio of Ga3+ to Al3+ and the Y2.9Al4.25Ga0.75O12:Ce3+0.1 phosphor showed the best performance on PL. However, the optimum concentration of Y3?yAl5?xGaxO12:Ce3+y phosphors is x?=?1.5 and y?=?0.04 when they were excited by cathode ray. 相似文献
18.
Epitaxial layers of (Sn2)1?x(InSb)x solid solutions were grown from an indium-based solution melt confined between two horizontal GaAs substrates in a temperature interval from 325 to 200°C. Scanning microprobe and X-ray diffraction investigations of the GaAs-(Sn2)1?x(InSb)x heterostructures showed that crystallographic perfection of the epitaxial layers depends on the epitaxial growth conditions. 相似文献
19.
(ZnMg)2SiO4 powders was prepared by the sol-gel process, and the microstructure and dielectric properties of (Zn1−xMgx)2SiO4 microwave materials were investigated systematically. TG-DSC and XRD analyzes for gels indicate that the (ZnMg)2SiO4 with pure willemite phase could be obtained at low temperature of 850°C. Further, XRD illustrates that just small amounts
of Mg can be incorporated into Zn2SiO4 lattice, and the solid solution limit of Mg in Zn2SiO4 is about x = 0·1. By appropriate Mg substitution for Zn, the sintering range is widened and the sintering temperature of Zn2SiO4 ceramics can be lowered effectively. SEM shows that Mg-substitution for Zn can promote the grain growth of Zn2SiO4. Moreover, the microwave dielectric properties strongly depended on the substitution content of Mg and sintering temperatures.
(Zn0·8Mg0·2)2SiO4 dielectrics sintered at 1170°C show the condense microstructure with small uniform grains and best microwave properties:
ɛ
r = 6·3, Q × f = 189800 GHz and τ
f = −63 ppm/°C. 相似文献
20.
A. Jiménez-Vázquez R. Falconi H. Takeya B. Ouladdiaf M. ElMassalami 《Journal of Materials Science: Materials in Electronics》2018,29(18):15411-15415
DyNi\(_{2}\)B\(_{2}\)C superconducts at \(T_{c} \approx 6\,{\text{K}}\) and orders antiferromagnetically at \(T_{N}\approx 10\,{\text{K}}.\) Its non-superconducting isomorph DyCo\(_{2}\)B\(_{2}\)C is a ferromagnet with \(T_{C}\approx 6\,{\text{K}}.\) With the aim of mapping out the magnetic properties, in particular magnetic structures, of their solid solutions, we synthesized \(^{11}\)B-enriched Dy(Co\(_{x}\)Ni\(_{1-x}\))\(_{2}\)B\(_{2}\)C (\(x=0.2,0.4,0.6,0.8\)). We investigated the evolution of their magnetic, thermal and transport properties by means of the magnetization, resistivity, specific heat and neutron diffraction techniques. Their crystal structures were confirmed to be ThCr\(_{2}\)-Si\(_{2}\)-type tetragonal (I4/mmm) phase. The magnetic structure was found to be antiferromagnetic with k0.2 = (0, 0, 1) for x = 0.2; helicoidal with k\(_{0.4}\) = (0, 0, 0.49) and k\(_{0.6}\) = (0, 0, 0.46) for, respectively, x = 0.4 and 0.6 and ferromagnetic with k\(_{0.8}\) = (0, 0, 0) for x = 0.8. We discuss the evolution of such magnetic modes assuming a scenario of an idealized one-dimensional chain of transverse magnetic moments. 相似文献