共查询到20条相似文献,搜索用时 12 毫秒
1.
Thiago S. Ribeiro José M. Sasaki Igor F. Vasconcelos 《Journal of Materials Science》2012,47(6):2630-2636
Structural characterization of nanosized Fe-doped semiconducting oxide SnO2 is reported. Samples of Sn1?x Fe x O2?y (with x ranging from 0.11 to 0.33) were processed in a planetary ball mill, subsequently HCl-washed to eliminate metallic iron impurities introduced by the milling tools, and characterized by X-ray diffraction and Mössbauer spectroscopy. Results showed that Fe enters the host matrix randomly replacing Sn in octahedral sites regardless of iron concentration. It has been found the presence of oxygen deficient iron sites attributed to the stoichiometric unbalance of precursor materials used in the milling process. It is known that structural features like particle size and residual microstrain are highly affected by the milling process. Values of average particle sizes as calculated by Scherrer’s method alone decreased with increasing Fe concentration. This result was shown, by means of the Williamson-Hall correction method, to be misleading as a large degree of microstrain is expected for mechanically milled powders. In fact, corrected values of average particle sizes turned out to be reasonably homogeneous regardless of iron content and milling time with no consistent trend. Residual microstrain, on the other hand, was found to increase with iron content giving way to the conclusion that broadening of diffraction peaks are mostly due to increasing microstrain as a function of iron doping and milling time. Williamson-Hall analysis also showed a large degree of particle size inhomogeneity. Milling of undoped SnO2 showed that this inhomogeneity is due mostly to doping as opposed to milling. 相似文献
2.
A. A. Bush V. Ya. Shkuratov K. E. Kamentsev V. M. Cherepanov 《Inorganic Materials》2013,49(3):296-302
Co1 ? x Ni x Cr2O (0 ≤ x ≤ 1) ceramic samples have been characterized by X-ray diffraction and relative dielectric permittivity ?(T), loss tangent tan δ(T) (0.1–200 kHz), and thermally stimulated depolarization current (TSDC) measurements in the range 100–350 K. The samples were shown to consist of spinel solid solutions with a cubic (0 < x ≤ 0.98) or tetragonal (0.99 ≤ x < 1) structure. Increasing the Ni content of the samples from 0 to 100 at % increases their tanδ and 1/ρ by three to four orders of magnitude. The ?(T), tan δ(T), and TSDC of the samples with 0.2 ≤ x ≤ 0.6 have anomalies at T 1 ~ 220 K and T 2 ~ 240 K, which point to a transition to a polar state below T 2. Samples containing 1–4 at % 57Fe as an impurity were characterized by Mössbauer spectroscopy in the range 54–330 K and were shown to be magnetically ordered at 78 K. We conclude that the solid solutions have ferroelectric properties with a Curie temperature T 2 and magnetoelectric multiferroic properties. 相似文献
3.
Thermally Stimulated Conductivity (TSC) has been used to analyse defects in the novel material -In2S3. These films were deposited using spray pyrolysis technique, varying In:S concentration ratio in the spraying solution. TSC measurements allowed the study of electrical property and non-radiative transitions, due to the defects present in the material. TSC spectra revealed four defects with their prominence varying with In:S concentration ratio. Samples with lower In concentration showed the presence and prominence of indium vacancy. A chemical impurity level due to the presence of chlorine was also detected. Even though sulphur vacancy existed in all the samples irrespective of the variation of In:S concentration ratio its effect decreased with the increase of sulphur concentration. Another defect level was also detected from TSC measurements at high temperature that was attributed to the replacement of sulphur by oxygen which was maximum in films prepared from a spray solution of In:S = 2:3 and minimum for 2:8. This high temperature defect level acts as a neutral center while all the other three levels were seen to be coulomb repulsive. Results from XPS analysis are found to be in good agreement with the TSC results. 相似文献
4.
Chemical and structural properties of oxide precipitates formed from FeSO4 solution were investigated using X-ray diffraction and57Fe Mössbauer spectroscopy. The hydrolysis of urea at elevated temperature was used for the generation of OH– ions during the precipitation process. The formation of particular oxide phase in the precipitate is strongly dependent on the concentrations of FeSO4 and urea, as well as on the rate of oxygenation. The phase analysis of precipitates showed the presence of different oxide phases, such as goethite, lepidocrocite, hematite and magnetite, and in one sample of a small amount of siderite. Only substoichiometric magnetite, Fe3–x
O4, was detected. Significant differences in the Mössbauer spectrum of goethite were observed, due to a very small particle size, the degree of crystallinity and/or different content of structurally bonded water. The correlation between the Mössbauer spectra of precipitated goethite and goethite formed during the atmospheric corrosion of steel is discussed. 相似文献
5.
Z. U. Jabua 《Inorganic Materials》2009,45(12):1394-1398
A process is described for the growth of thin crystalline α-Dy2S3 films by thermal evaporation from separate dysprosium and sulfur sources. The films were doped with Pb, and their reflection
and transmission spectra were measured at room temperature and photon energies in the range (0.3−5.2) × 10−19 J. The α-Dy2S3 films were shown to have an exponential absorption edge. The photoconductivity of the doped films was measured at photon
energies in the range (0.3−5.2) × 10−19 J and temperatures from 115 to 400 K. 相似文献
6.
Co x Ni1–x Al2O4 (x = 0, 0.25, 0.5, 0.75, 1) aluminate spinels have been prepared by solid-state reactions and their crystal structures have been refined by the Rietveld method. We have analyzed whether the results are consistent with theoretical relationships stemming from the hard sphere model. Using high- and low-temperature X-ray diffraction measurements, we have obtained the temperature dependences of the unit-cell parameters for the synthesized compounds and determined their thermal expansion coefficients. The rate of cation exchange reactions has been shown to be very slow at temperatures below 200°C. 相似文献
7.
Yu. O. Lekina I. S. Glazkova A. A. Belik I. A. Presniakov A. V. Sobolev 《Inorganic Materials》2018,54(10):990-997
This paper presents results of a 57Fe probe Mössbauer spectroscopy study of the BiNi0.9657Fe0.04O3 nickelate. The spectra measured above its TN demonstrate that Fe3+ cations heterovalently substitute for Ni2+ nickel (←Fe3+), being stabilized on four sites of the nickel sublattice in the structure of BiNiO3. Calculations in an ionic model with allowance for monopole and dipole contributions to the electric field gradient indicate that the parameters of electric hyperfine interactions between 57Fe probe atom nuclei reflect the specifics of the local environment of the nickel in the structure of the unsubstituted BiNiO3 nickelate. Below TN, Mössbauer spectra transform into a complex Zeeman structure, which is analyzed in terms of first-order perturbation theory with allowance for electric quadrupole interactions as a small perturbation of the Zeeman levels of the 57Fe hyperfine structure, as well as for specific features of the magnetic ordering of the Ni2+ cations in the nickelate studied. 相似文献
8.
TiO2–NiO and TiO2–WO3 nanocomposites were prepared by hydrothermal and surface modification methods. The samples were analyzed using X-ray diffraction, Scanning Electron Microscope images, Transmission Electron Microscope, Energy dispersive analysis, Zeta potential, Electrophoretic mobility and Photocatalysis activity measurement. XRD data sets of TiO2–NiO, TiO2–WO3 powder nanocomposite have been studied for the inclusion of NiO, WO3 on the anatase-rutile mixture phase of TiO2 by Rietveld refinement. The cell parameters, phase fraction, the average grain size, strain and bond lengths between atoms of individual phases have been reported in the present work. Shifted positional co-ordinates of individual atoms in each phase have also been observed. 相似文献
9.
L. D. Ivanova L. I. Petrova Yu. V. Granatkina A. G. Mal’chev I. Yu. Nikhezina D. S. Nikulin O. A. Raikina 《Inorganic Materials》2016,52(8):755-761
Using scanning electron and optical microscopies, we have studied the morphology of fracture surfaces and microstructure of samples of an Sb2Te3–Bi2Te3 solid solution (p-type conductivity) prepared by hot pressing and extrusion of granules produced through melt solidification in liquids. All of the samples were found to contain an additional phase in the form of a tellurium-based eutectic, and their macroscopic structure was shown to depend on the granule comminution procedure. The electrical conductivity, Seebeck coefficient, and thermal conductivity of the samples have been measured in the range 100–700 K. We have obtained materials with the highest dimensionless thermoelectric figure of merit ZT ~ 1.0 at temperatures from 300 to 440 K. 相似文献
10.
I. A. Auwal A. D. Korkmaz M. D. Amir S. M. Asiri A. Baykal H. Güngüneş S. E. Shirstah 《Journal of Superconductivity and Novel Magnetism》2018,31(1):151-156
Barium hexaferrite is a well-known hard magnetic material. Doping using nonmagnetic cation such as Zn2+ were found to enhance magnetization owing to preferential tetrahedral site (4 f 1) occupancy of the zinc. However, the distribution of cations in hexaferrites depends on many factors such as the method of preparation, nature of the cation, and chemical composition. Here, Zn-doped barium hexaferrites (Ba1?xZnxFe12O19) were synthesized by sol-gel method. In this study, we summarized the magnetic properties of Ba1?xZnxFe12O19 (x = 0, 0.1, 0.2, 0.3) BaM, investigated by Mössbauer spectroscopy. Moreover, cation distribution was also calculated for all the products. Mössbauer parameters were determined from 57Fe Mössbauer spectroscopy and according to it, the replacement of Ba-Zn affects all parameters such as isomer shift, the variation in line width, hyperfine magnetic field, and quadrupole splitting. Cation distribution revealed the relative area of undoped BaM, 12k, 2a, and 4 f 2 positions which are close to theoretical values. 相似文献
11.
The crystal structure of a previously unknown Np(V) sesquioxalate, Na4(NpO2)2(C2O4)3·2H2O was studied. The crystal structure consists of neptunyl(V) cations, sodium cations, oxalate anions, and water molecules of crystallization. Neptunyl(V) cations and oxalate ions form anionic chains [(NpO2)2(C2O4)3] n 4n? . The coordination polyhedron (CP) of Np (pentagonal bipyramid) contains two apical “yl” oxygen atoms and five equatorial O atoms of three oxalate ions. The CP of Na(1) and Na(2) cations are combined through the common edges into zigzag chains in the [010] direction. Two independent oxalate ions are tridentate and tetradentate ligands. 相似文献
12.
13.
A. I. Dmitriev 《Technical Physics Letters》2018,44(2):137-140
The kinetics of spontaneous demagnetization in nanoparticles of the exotic epsilon-phase of indium-doped iron(III) oxide (ε-In0.24Fe1.76O3) has been studied using the method of accelerated testing of magnets for temporal stability in a magnetization-reversal field. Time dependences of the magnetization of nanoparticles measured in a wide range of magnetic fields exhibited rectification in semilogarithmic coordinates. The dependence of the magnetic viscosity on the magnetic field has been measured and used for determining the fluctuation field and activation volume. A relationship between the magnetic viscosity and magnetic noise caused by random thermoinduced magnetization reversal in separate nanoparticles is established. 相似文献
14.
15.
Zhanqing Liu Zupei Yang Xiaolian Chao 《Journal of Materials Science: Materials in Electronics》2016,27(9):8980-8990
La2/3Cu3Ti4O12 (LCTO) precursor powders were synthesized by the sol–gel method. Effect of sol conditions and sintering process on microstructure and dielectric properties of LCTO powders or ceramics were investigated systematically. The optimum sol conditions for the synthesis of precursor powders were as follows: the Ti4+ concentration of 1.00 mol/L, the molar ratio of water and titanium of 5.6:1 and the sol pH of 1.0, respectively. After sintered at 1105 °C for 15 h, the LCTO ceramics exhibited more homogeneous microstructure, much higher dielectric constant (ca 09–1.6 × 104) and lower dielectric loss (ca 0.057). The higher dielectric constant of the LCTO ceramics might be due to the internal barrier layer capacitor effect. The LCTO ceramics showed two kinds of conductivity activation energy for grain boundary conductivity from complex impedance analysis. The transition temperature of two activation energy values occured between 170 and 210 °C. The temperature range of 170–210 °C was critical pseudocritical region of the dielectric constant, dielectric loss and activation energy. Furthermore, it was concluded that the grain boundary play an important role for electrical properties. 相似文献
16.
The formation rate of polymorph III during the II → III phase transition in single crystals of the KNO3-RbNO3 solid solutions containing 2.5, 5, and 10 wt % RbNO3 has been measured as a function of temperature using optical microscopy. The formation rate is shown to increase with increasing
ΔT (ΔT = T
tr − T
0, where T
tr is the transition temperature and T
0 is the equilibrium temperature). Best fit equations are derived for describing this process, and its activation energy is
determined. 相似文献
17.
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
18.
Banjong Boonchom 《International Journal of Thermophysics》2010,31(2):416-429
The kinetics of thermal dehydration of Mg3(PO4)2 · 8H2O was investigated using thermogravimetry at four different heating rates. The activation energies of the dehydration step
of Mg3(PO4)2 · 8H2O were calculated through the isoconversional Ozawa and Kissinger-Akahira-Sunose (KAS) methods and iterative methods, which
were found to be consistent and indicate a single mechanism. The possible conversion function of the dehydration reaction
for Mg3(PO4)2 · 8H2O has been estimated through the Coats and Redfern integral equation, and a better kinetic model such as random nucleation
of the “Avrami–Erofeev equation (A
3/2 model)” was found. The thermodynamic functions (ΔH*, ΔG*, and ΔS*) of the dehydration reaction are calculated by the activated complex theory and indicate that it is a non-spontaneous process
when the introduction of heat is not connected. 相似文献
19.
Ca2.8Ln0.2Co4O9 + δ (Ln = La, Nd, Sm, Tb-Er) solid solutions have been prepared via a citrate route and their structural parameters have been determined. Their thermal expansion, thermoelectric power, thermal conductivity, and electrical conductivity have been measured above room temperature. The results demonstrate that all of the materials obtained are p-type semiconductors. Their unit-cell parameters decrease with a decrease in the ionic radius of the Ln3+ cation substituted for Ca2+, and their thermoelectric power increases with an increase in the number of f electrons of the Ln3+ cation. We have determined the electron and phonon contributions to the thermal conductivity of the materials and evaluated the thermoelectric power factor and thermoelectric figure of merit of the oxide ceramics. The highest thermoelectric power factors are offered by the Ca2.8Tb0.2Co4O9 + δ and Ca2.8Er0.2Co4O9 + δ solid solutions: 0.27 and 0.29 mW/(m K2), respectively, at T = 1100 K. 相似文献
20.
Semih Seyyidoğlu Macit Özenbaş Necmeddin Yazıcı Ayşen Yılmaz 《Journal of Materials Science》2007,42(15):6453-6463
In this study, ZrP2O7 was synthesized by the solid state reaction of ZrO2 and NH4H2PO4 at 900 °C. Then, in set 1; 10, 5, 1, 0.5, 0.1, 0.05, 0.03% previously prepared Sr2P2O7 were doped into ZrP2O7, and Sr2P2O7 slightly affect the unit cell parameter of cubic ZrP2O7 (a = 8.248(6)–8.233(8) Å). The reverse of this process was also applied to Sr2P2O7 system (set 2). ZrP2O7 changes the unit cell parameters of orthorhombic Sr2P2O7 in between a = 8.909(5)–8.877(5) Å, b = 13.163(3)–13.12(1) Å, and c = 5.403(2)–5.386(4) Å. Analysis of the vibrations of the P2O 7 4? ion and approximate band assignments for IR and Raman spectra are also reported in this work. Some coincidences in infrared and Raman spectra both sets were found and strong P–O–P bands were observed. Surface morphology, EDX analysis, and thermoluminescence properties of both sets were given the first time in this paper. 相似文献