共查询到20条相似文献,搜索用时 46 毫秒
1.
Yogesh Kumar K. L. Yadav 《Journal of Materials Science: Materials in Electronics》2018,29(11):8923-8936
Magnetoelectric (ME) composites consisting of K0.5Na0.5NbO3 (KNN) as ferroelectric phase and CoMn0.2Fe1.8O4 (CMFO) as ferrite phase with general formula (x) CoMn0.2Fe1.8O4–(1???x) K0.5Na0.5NbO3 (x?=?10, 20, 30, 40 and 50 wt%) were synthesized using solid state reaction method. X-ray diffraction analysis asserts the existence of component phases including spinel phase of CMFO and orthorhombic phase of KNN. Field emission scanning electron microscopy has been used for studying the morphology and calculation of average grain size. The temperature dependent dielectric properties including dielectric constant (\(\varepsilon ^{\prime}\)) and dielectric loss (tan δ) at different frequencies has been studied and both are found to increase with incorporation of CMFO. Magnetic hysteresis loops have been measured at temperatures of 300 and 5 K. Variation of magnetization versus temperature has been studied in field cooled and zero field cooled modes. Polarization versus electric field (P–E) hysteresis loops are obtained at room temperature indicating presence of ferroelectric ordering in the composites at room temperature. The remnant polarization (2Pr) and coercive field (2Ec) are found to decrease linearly with incorporation of CMFO. ME voltage coefficient (αME) has been measured. The maximum value of αME is found to be 5.941 mV/cm-Oe for 10% CMFO–90% KNN bulk composite. 相似文献
2.
I. V. Levchenko I. B. Stratiychuk V. N. Tomashyk G. P. Malanych 《Inorganic Materials》2017,53(9):896-901
This paper presents results on the kinetics and mechanism of the physicochemical interaction of InAs, InSb, GaAs, and GaSb semiconductor surfaces with (NH4)2Cr2O7–HBr–C4H6O6 etching solutions under reproducible hydrodynamic conditions in the case of laminar etchant flow over a substrate. We have identified regions of polishing and nonpolishing solutions and evaluated the apparent activation energy of the process. The surface morphology of the crystals has been examined by microstructural analysis after chemical etching. The results demonstrate that the presence of C4H6O6 in etchants helps to reduce the overall reaction rate and extend the region of polishing solutions. 相似文献
3.
BaFe12O19 hexaferrite films have been produced on thermally oxidized single-crystal silicon (SiO2/Si) substrates by sequential ion-beam sputtering of BaFe2O4 and α-Fe2O3 targets in an argon-oxygen atmosphere. Their crystal structure has been studied, and the origin of the impurity phases forming during heat treatment has been identified. The results show that heat treatment may lead to the formation of eutectic melts. As a result, the hexaferrite films may contain spherulites. 相似文献
4.
Keisuke Yasuda Toshiyuki Masui Takahiro Miyamoto Nobuhito Imanaka 《Journal of Materials Science》2011,46(11):4046-4052
Catalytic combustion of methane was investigated on Pt and PdO-supported CeO2–ZrO2–Bi2O3/γ-Al2O3 catalysts prepared by a wet impregnation method in the presence of polyvinylpyrrolidone. The catalysts were characterized
by X-ray fluorescence analysis, X-ray powder diffraction, X-ray photoelectron spectra, transmission electron microscopy, and
BET specific surface area measurements. The Pt/CeO2–ZrO2–Bi2O3/γ-Al2O3 and PdO/CeO2–ZrO2–Bi2O3/γ-Al2O3 catalysts were selective for the total oxidation of methane into carbon dioxide and steam, and no by-products such as HCHO,
CO, and H2 were obtained. The catalytic activities of the PdO/CeO2–ZrO2–Bi2O3/γ-Al2O3 catalysts were relatively higher than those of the Pt-supported catalysts, due to the facile re-oxidation of metallic Pd
into PdO based on lattice oxygen supplied from the CeO2–ZrO2–Bi2O3 bulk. A decrease in the calcination temperature during the preparation process was found to be effective in enhancing the
specific surface area of the catalysts, whereby particle agglomeration was inhibited. Optimization of the PdO amount and calcination
temperature enabled complete oxidation of methane at temperatures as low as 320 °C on the 11.6 wt% PdO/CeO2–ZrO2–Bi2O3/γ-Al2O3 catalyst prepared at 400 °C. 相似文献
5.
Laura Londaitzbéhère Sylvie Lartigue-Korinek Leo Mazerolles 《Journal of Materials Science》2017,52(10):5489-5502
New compositions in the melt-grown eutectic ceramics field are investigated for thermomechanical applications. This paper is focused on the Al2O3–Sm2O3–(ZrO2) system. The studied compositions give rise to interconnected microstructures without anisotropy along the growth direction. At variance with the binary eutectic Al2O3–SmAlO3, the homogeneity of the microstructure of the Al2O3–SmAlO3–ZrO2 ternary eutectic is less sensitive to the growth rate. Interfaces between the alumina and perovskite phases are investigated by high-resolution transmission electron microscopy (TEM). They are semi-coherent. In stepped interfaces, the facets are parallel to dense planes of each phase. The steps have a dislocation character and may accommodate both misfits. The ternary eutectic displays a very good creep behaviour with strain rates very close to those obtained on other previously studied eutectics in the Al2O3–RE2O3(RE = Y, Gd, Er)–ZrO2 systems. The deformation micromechanisms are analysed by TEM in the three eutectic phases. After creep, dislocations are present in every phase. The activation of unusual slip systems (pyramidal slip in the alumina phase) shows that high local stresses can be reached. The presence of dislocation networks with low energy configurations is consistent with predominance of dislocation climb processes controlled by bulk diffusion. 相似文献
6.
Abdeslam Chagraoui Imane Yakine Abdelmjid Tairi Abdenajib Moussaoui Mohamed Talbi Mohamed Naji 《Journal of Materials Science》2011,46(16):5439-5446
A glass-forming domain is found and studied within Bi2O3–Sb2O3–TeO2 system. The glasses composition were obtained in pseudo-binary xSbO1.5, (1−x)TeO2 for 0.05 ≤ x ≤ 0.20. The constitution of glasses in the system Sb2O3–TeO2 was investigated by DSC, Raman, and Infrared spectroscopy. The influence of a gradual addition of the modifier oxides on
the coordination geometry of tellurium atoms has been elucidated based Infrared and Raman studies and showed the transition
of TeO4, TeO3+1, and TeO3 units with increasing Sb2O3 content. XRD results reveal the presence of three crystalline: γ-TeO2, α-TeO2, and SbTe3O8 phases during the crystallization process. The density of glasses has been measured. The investigation in the ternary system
by the solid state reaction using XRD reveals the existence of a solid solution Bi1−x
Sb1−x
Te2x
O4 isotopic to BiSbO4 with 0 ≤ x ≤ 0.1. 相似文献
7.
Hiroyuki Hayashi Rong Huang Fumiyasu Oba Tsukasa Hirayama Isao Tanaka 《Journal of Materials Science》2011,46(12):4169-4175
The interface between an Mn-doped γ-gallium oxide (Ga2O3) thin film and an MgAl2O4 (001) substrate has been investigated using high-resolution transmission electron microscopy (HRTEM), high-angle annular
dark-field scanning transmission electron microscopy (HAADF-STEM), and first-principles calculations. A high-quality Mn-doped
γ-Ga2O3 film with a defective spinel structure has been epitaxially grown by pulsed laser deposition. The γ-Ga2O3 crystal shows an uniform tetragonal distortion with a tetragonality of 1.05 throughout the film thickness of 75 nm. HRTEM
and HAADF-STEM observations reveal that the γ-Ga2O3 and MgAl2O4 crystals form a coherent interface without any interfacial layers or precipitates. The atomistic structure and energies are
theoretically evaluated for the interfaces with two types of termination plane, i.e., Mg- and Al2O4-termination of MgAl2O4. The cation sublattice is found to be continuous for both interfaces despite the defective spinel structure of Mn-doped γ-Ga2O3 with some vacant cation sites. The Al2O4-termination shows a lower interfacial energy than the Mg-termination under most conditions of the chemical potentials. This
behavior is attributed to the energetic preference of the Mn–Al2O4 local configuration at the interface. 相似文献
8.
Ekkehard Krüger 《Journal of Superconductivity and Novel Magnetism》2010,23(2):213-223
It is shown that the ceramic superconductor YBa2Cu3O7 as well as the superconducting intermetallic compound MgB2 possesses a narrow, partly filled “superconducting band” with Wannier functions of special symmetry in their band structures.
This result corroborates previous observations about the band structures of numerous superconductors and non-superconductors
showing that evidently superconductivity is always connected with such superconducting bands. These findings are interpreted
in the framework of a nonadiabatic extension of the Heisenberg model. Within this new group-theoretical model of correlated
systems, Cooper pairs are stabilized by a nonadiabatic mechanism of constraining forces effective in narrow superconducting
bands. The formation of Cooper pairs in a superconducting band is mediated by the energetically lowest boson excitations in
the considered material that carry the crystal-spin angular momentum 1⋅ℏ. These crystal-spin-1 bosons are proposed to determine whether the material is a conventional low-T
c or a high-T
c superconductor. This interpretation provides the electron–phonon mechanism that enters the BCS theory in conventional superconductors. 相似文献
9.
A. V. Trukhanov A. I. Stognij N. N. Novitskii S. V. Trukhanov V. A. Ketsko 《Inorganic Materials》2011,47(9):1025-1028
Films 150–200 nm in thickness, with the nominal composition Mg(Fe0.8Ga0.2)2O4 − δ have been grown on (100) single-crystal silicon substrates by ion-beam sputtering in vacuum. The effect of growth and annealing
conditions on the crystal structure and morphology of the films has been studied, and the thermal conditions for the growth
of spinel-structure films have been optimized. 相似文献
10.
I. V. Levchenko I. B. Stratiychuk V. N. Tomashyk G. P. Malanych A. S. Stanetskaya 《Inorganic Materials》2017,53(8):781-785
We have studied the nature and kinetics of the chemical interaction of InAs, InSb, GaAs, and GaSb crystals with aqueous (NH4)2Cr2O7–HBr solutions. The dissolution rate of the crystals has been measured as a function of etchant composition, solution stirring rate, and temperature. The results demonstrate that the dissolution rate of the semiconductors is diffusion-limited. We have determined the composition ranges of polishing solutions, optimized their compositions, and found conditions for the dynamic chemical polishing of the semiconductors. Ultrasmooth polished semiconductor surfaces have been obtained, with R a ≈ 1 nm. 相似文献
11.
M. K. Suresh P. R. S. Wariar J. K. Thomas Sam Solomon 《Journal of Materials Science: Materials in Electronics》2010,21(11):1191-1194
(Ca2Mg3)(X1.75Sb0.25)TiO12 [X = Nb and Ta] ceramics are prepared through the conventional solid-state route. The samples are calcined at 1,100 and 1,180 °C,
and are sintered at 1,250 and 1,375 °C. The substitution of Sb decreases the calcination and sintering temperatures of pure
(Ca2Mg3)(Nb/Ta)2TiO12. The structure of the samples is analyzed using X-ray diffraction method. The microstructure of the sintered pellet is studied
using scanning electron microscopy. The dielectric properties such as dielectric constant (εr), quality factor (Quxf) and temperature coefficient of resonant frequency (τf) are measured in the microwave frequency region. By Sb substitution, thermal stability is achieved, with the increase in
dielectric constant, without much change in the quality factor. The materials have intense emission lines in the wavelength
region 500–700 nm. The compositions have good microwave dielectric properties and photoluminescence and hence are suitable
for dielectric resonator and ceramic laser applications. 相似文献
12.
Wilfried Hermes Stefan Linsinger Sudhindra Rayaprol Selcan Tuncel Rolf-Dieter Hoffmann Reinhard K. Kremer Ove Jepsen Rainer Pöttgen 《Journal of Superconductivity and Novel Magnetism》2011,24(5):1585-1592
The intermetallic compounds RE
2Cu2Mg and RE
2Pd2Mg (RE=La, Ce) were prepared and characterized by magnetic susceptibility and heat-capacity measurements. They crystallize with
an ordered U3Si2 type structure (space group P4/mbm) and the cerium compounds contain stable trivalent cerium ions, which undergo antiferromagnetic ordering at ∼7.5 and ∼4 K,
respectively. In high magnetic fields Ce2Cu2Mg exhibits spin reorientation with critical field strength of 40 kOe at 5 K. The data are compared to the non-magnetic isotypic
compounds La2
T
2Mg (T=Cu, Ni, Pd) and to the already reported intermediate valent Ce2Ni2Mg. 相似文献
13.
Wenbo Yue Xiaoxiang Xu Zixue Su John T. S. Irvine Yongcun Zou Yunling Liu Wuzong Zhou 《Journal of Materials Science》2012,47(5):2146-2154
Two mesoporous oxide composites of Nd2O3–SiO2 and NdOCl–SiO2 were synthesized using SBA-15 as a template and neodymium nitrate or neodymium chloride as a precursor. The porous Nd2O3–SiO2 with a SBA-15-like structure has amorphous walls and the porous NdOCl–SiO2 with a replicated structure of SBA-15 has crystalline walls. These porous materials were characterized by X-ray diffraction,
transmission electron microscopy and nitrogen adsorption/desorption. They exhibited significant proton conductivities in the
presence of moisture at low temperatures and the highest conductivity observed was 4.55 × 10−4 S/cm at 47 °C in wet air (RH = 28.6%). 相似文献
14.
T. Shimazu H. Maeda E. H. Ishida M. Miura N. Isu A. Ichikawa K. Ota 《Journal of Materials Science》2009,44(1):93-101
High-damping materials are widely used in engineering fields. In order to increase the precision of vibration control to different
levels, high-damping materials with high-rigidity are required. This study attempts to develop a new high-damping high-rigidity
material using ductile ceramics based on the Al2TiO5–MgTi2O5 system, which has many continuous microcracks along the grain boundaries. Ductile ceramics have high internal friction (Q
−1 = 0.01–0.037), but very low rigidity (<10 GPa). The rigidity of Al2TiO5–MgTi2O5 ceramics was improved by combining them with a polymer such as acrylic resin. The Young’s modulus and internal friction of
the composites of Al2TiO5–MgTi2O5 ceramics and acrylic resin are investigated. They show high-damping capacity (Q
−1 = 0.03–0.04) with high rigidity (E = 50–60 GPa), and their properties depend on those of the polymer. Thus, the composites fabricated using the above method
can serve as high-damping high-rigidity materials. 相似文献
15.
Jun Wang Changrong Zhou Qingning Li Weidong Zeng Jiwen Xu Guohua Chen Changlai Yuan Guanghui Rao 《Journal of Materials Science》2018,53(12):8844-8854
Lead-free ceramics (1???x)Bi0.5Na0.5TiO3–xSr0.85Bi0.1TiO3 (BNT–xSBT, x?=?0.4, 0.5, 0.6 and 0.7) were prepared by a solid-state reaction process. Coexistence of ferroelectric relaxation at low temperature and Maxwell–Wagner dielectric relaxation at high temperature was revealed for the first time in this system. Meanwhile, hysteresis-free P–E loops combined with a very high piezoelectric strain coefficient (d33) of 1658 pC/N concurrently with large electrostrictive coefficient Q?=?0.287 m4C?2 were achieved. The ferroelectric relaxor behavior and large electrostrictive strain might be linked to easy reorientation and reversal of ergodic PNRs and the combined effect of Bi off-center position and lone pair electrons. 相似文献
16.
Xiangyu Meng Xiansong Liu Chaocheng Liu Cong Zhang Haohao Li Khalid Mehmood Ur Rehman 《Journal of Materials Science: Materials in Electronics》2018,29(2):881-886
In the case of Ti4+ remain unchanged, the Ca2+ substituted Ba0.75?xCaxLa0.25Fe11.6Co0.25Ti0.15O19 (0?≤?x?≤?0.05) were prepared by conventional solid-state reaction method at temperature of 1280 °C. A ball-to-power weight ratio of 10:1. Their crystal structure and magnetic properties were mainly investigated. The results show that the single magnetoplumbite phase structure transformed into the multiphase structure. Meanwhile, the small amount of α-Fe2O3 phase existed in M-type phase. The micrographs were observed by a field emission scanning electron microscopy (SEM). Vibrating sample magnetometer (VSM) was used to analyze the magnetic properties. The saturation magnetization (M s ) first increases then decreases when x from 0 to 0.03. But, when x from 0.03 to 0.05, the saturation magnetization (M s ) first increases then decreases too. The maximum value is at x?=?0.04 (M s ?=?70.73 emu/g). The value of coercivity (H c ) first increases then decreases when x from 0 to 0.04. But, the value increased when x from 0.04 to 0.05. The maximum value is at x?=?0.02 (H c ?=?1691 Oe). 相似文献
17.
Hui-Juan Wang Tilman Zscheckel Bo-Tao Li Hui-Xing Lin Christian Bocker Christian Rüssel Lan Luo 《Journal of Materials Science》2017,52(3):1330-1347
Crystallization and microstructure of glasses with the molar compositions 1MgO·1.2Al2O3·2.8SiO2·1.2TiO2·xLa2O3 (x = 0.1 and 0.4) were thermally treated at different temperatures in the range from 950 to 1250 °C and then analyzed by X-ray diffraction and scanning electron microscopy, in combination with energy-dispersive X-ray spectroscopy and electron backscatter diffraction. It was found that the microstructure is first homogeneous with the precipitation of randomly distributed crystals and then indialite domains with embedded perrierite and rutile crystals are formed. For higher temperatures or prolonged times, more domains appear and expand into the bulk of the sample. Finally, the entire sample consists of the indialite domains and the boundaries that are enriched in rutile, perrierite, and magnesium aluminotitanate. Nevertheless, very distinct differences are observed between the samples with different La2O3 concentrations. For the sample with x = 0.4, the domains were detected at lower temperatures, while the quantity and size of the domains increase faster due to the promoted precipitation of indialite. For the sample with x = 0.1, in addition to the domain boundaries, secondary boundaries between the “regions” (assemblages of the domains) are observed in a larger length scale. The average size of the crystalline phases found between the “regions” is larger than that typically observed at the domain boundaries. The sizes of the crystals at the boundaries decrease with higher concentrations of La2O3, and the crystals (especially perrierite) within the domains become larger, resulting in a more homogeneous microstructure. This results in better dielectric properties, i.e., much higher quality factor for the sample with x = 0.4 in comparison to that with x = 0.1 after heat-treatment at 1150 or 1250 °C. 相似文献
18.
Crystals of (FeIn2S4)1 ? x (In2S3) x solid solutions consisting of large blocks have been grown by directional solidification (horizontal Bridgman process). FeIn2S4, In2S3, and the solid solutions are shown to crystallize in the spinel structure. The composition dependence of their unit-cell parameter a follows Vegard's law. The local states of the Fe ions in the solid solutions have been studied by Mössbauer spectroscopy in a transmission geometry. 相似文献
19.
The dc conductivity of the glasses in the Fe2O3-Bi2O3-K2B4O7 system was studied at temperatures between 223 and 393 K. At temperatures from 300 to 223 K, T–1/4 (T is temperature) dependence of the conductivity was found, however, both Mott variable-range hopping and Greaves intermediate range hopping models are found to be applicable. Mott and Greaves parameters analysis gave the density of states at Fermi level N (EF) = 3.13 × 1020–21.01 × 1020 and 1.93 × 1021–16.39 × 1021 cm–3eV–1 at 240 K, respectively. The variable-range hopping conduction occurred in the temperature range T = 300–223 K, since WD was found to be large (WD = 0.08–0.14 eV for these glasses) and dominated the conduction at T < 300 K. 相似文献
20.
Lead-free piezoelectric ceramics (1 − x)Bi0.5Na0.5TiO3–xBaNb2O6 (BNT–BN100x), a new member of the BNT-based group, was prepared by conventional solid state reaction. X-ray diffraction showed that BaNb2O6 (BN) diffused into the lattice of Bi0.5Na0.5TiO3 to form a solid solution with perovskite-type structure. The temperature dependence of dielectric constant εr revealed that the solid solution underwent two phase transitions from ferroelectric to anti-ferroelectric and anti-ferroelectric
to paraelectric. Both the transition temperature T
d and T
m were shifted to lower with the increasing content of BaNb2O6. The temperature dependence of dielectric constant at different frequency revealed that the solid solution exhibited obviously
dielectric relaxation characteristics. The sample with x = 0.6 mol% exhibited excellent electrical properties, piezoelectric constant d
33 = 94 pC/N; electromechanical coupling factor k
p = 0.185. The results showed that BNT–BN100x ceramics were good candidates for use as lead-free piezoelectric ceramics. 相似文献