共查询到20条相似文献,搜索用时 31 毫秒
1.
A. A. Zatsiupa L. A. Bashkirov I. A. Vialikanava G. S. Petrov S. V. Shevchenko 《Inorganic Materials》2016,52(4):361-366
Bi2–хLaхFe4O9 and Bi2Fe4–2xTixCoxO9 ferrites have been prepared by solid-state reactions at a temperature of 1073 K. X-ray diffraction data indicate that, in the Bi2–хLaхFe4O9 system, the limiting degree of La3+ substitution for Bi3+ ions in Bi2Fe4O9 does not exceed 0.05 and that the limiting degree of substitution in the Bi2Fe4–2xTixCoxO9 system lies in the range 0.05 < x < 0.1. The specific magnetization and specific magnetic susceptibility of the samples have been measured at temperatures from 5 to 300 K in a magnetic field of 0.86 T. The field dependences of magnetization obtained for the Bi2–хLaхFe4O9 and Bi2Fe4–2xTixCoxO9 ferrites at temperatures of 300 and 5 K demonstrate that partial isovalent substitution of La3+ for Bi3+ ions in Bi2Fe4O9 and heterovalent substitution of Ti4+ and Co2+ ions for two Fe3+ ions leads to partial breakdown of the antiferromagnetic state and nucleation of a ferromagnetic state. 相似文献
2.
LiMn2-x
ErxO4 (x ≤ 0.02) materials were synthesized by a rheological phase reaction method. The thermal behavior of the materials was examined by thermogravimetric and differential scanning calorimetry. X-ray diffraction showed that the samples (x ≤ 0.02 ) exhibited the same phase as the pure spinel. The lattice parameter of the Er-doped spinel was smaller than that of the undoped one and decreased with increasing doping level. Cyclic voltammograms showed two reversible processes corresponding to the typical response of spinel LiMn2O4 and revealed an insertion-extraction reaction occurring at two stages in the 4-V region. The electrochemical performances of the samples were studied and displayed a better reversibility and cyclability.__________From Neorganicheskie Materialy, Vol. 41, No. 6, 2005, pp. 740–743.Original English Text Copyright © 2005 by Haowen Liu, Li Song, Kelli Zhang.This article was submitted by the authors in English. 相似文献
3.
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
4.
A series of Gd11–x–y Yb x Er y GeP3O26 germanate phosphates differing in the ratio of the Yb3+ and Er3+ active ions have been synthesized, and their luminescence spectra have been measured. According to X-ray diffraction characterization results, all of the synthesized germanate phosphates are single-phase and have a triclinic structure (sp. gr. P1). We have measured upconversion luminescence spectra due to the Er3+ 2H11/2, 4S3/2 → 4I15/2 and 4F9/2 → 4I15/2 radiative transitions in the synthesized gadolinium ytterbium erbium germanate phosphates and determined the luminescence upconversion energy yield (B en) in Gd11–x–y Yb x Er y GeP3O26. The effects of the concentrations and ratio of the dopants in the Gd11(GeO4)(PO4)3O10 germanate phosphate host on B en and the ratio of the luminescence intensities in the red and green spectral regions (R/G) have been assessed. 相似文献
5.
The structure of [80TeO2 + (20–x)MoO + xNd2O3] glasses, with x = 0, 4, 6, 10 and 12 mol%, is studied in this work. Raman scattering in the spectral range (−2000 to 3500 cm−1) and IR absorption spectra have been measured for crystalline TeO2 and glasses, and their assignments were discussed and compared. Many vibrational modes were found active in both Raman and IR and their assignments for crystalline TeO2 and for the glasses were discussed in relation to the tetragonal structure of crystalline α -TeO2. Nd2O3 was found to completely eliminate diffuse scattering and enhance the Raman scattering intensity. Anti-stokes Raman bands in the range −1460 cm− 1 to −1975 cm− 1 were observed for both (30Li2O + 70B2O3+ xNd2O3) glasses and [80TeO2 + (20−x)MoO + xNd2O3] glasses and were attributed to some emission processes due to the doping of the glasses with Nd2O3. 相似文献
6.
A. V. Shlyakhtina I. V. Kolbanev A. V. Knotko M. V. Boguslavskii S. Yu. Stefanovich O. K. Karyagina L. G. Shcherbakova 《Inorganic Materials》2005,41(8):854-863
The electrical conductivity of Ln2 + x
Zr2 − x
O7 − x/2 (Ln = Sm-Gd) solid solutions prepared from mechanically activated Ln2O3 and ZrO2 is shown to correlate with their structural properties. In the three systems, the x-T regions are determined in which electrical transport is dominated by oxygen-ion conduction. In the Sm2O3-ZrO2 system, ionic conductivities from 5 × 10−4 to 6 × 10−3 S/cm at 740°C are found in Sm2 + x
Zr2 − x
O7 − x/2 with 26.6, 33.3, 35.5, 37, and 40 mol % Sm2O3 prepared at 1450, 1530, and 1600°C. Eu2 + x
Zr2 − x
O7 − x/2 and Gd2 + x
Zr2 − x
O7 − x/2 containing 33.3 to 37 mol % Ln2O3 have 740°C ionic conductivities of 10−3 to ∼7.5 × 10−3 and 10−3 to 7 × 10−3 S/cm, respectively. The activation energy of conduction in Ln2 + x
Zr2 − x
O7 − x/2 (Ln = Sm-Gd), E
a = 0.84–1.04 eV, increases with the atomic number of Ln and x. The highest ionic conductivity is offered by the stoichiometric Ln2Zr2O7 (Ln = Sm-Gd) pyrochlores prepared at 1600°C, owing to the optimal concentration of LnZr + ZrLn antistructure pairs (∼5–22%). The grains in the ceramic samples studied range in size from 0.5 to 2 µm.__________Translated from Neorganicheskie Materialy, Vol. 41, No. 8, 2005, pp. 975–984.Original Russian Text Copyright © 2005 by Shlyakhtina, Kolbanev, Knotko, Boguslavskii, Stefanovich, Karyagina, Shcherbakova. 相似文献
7.
Cu2{(UO2)3[(S,Cr)O4]5}(H2O)17 crystals were prepared by evaporation of aqueous solutions. The crystal structure was solved by the direct method and refined to R
1 = 0.064 (wR
2 = 0.177) for 8120 reflections with ¦F
hkl¦ 4 ¦F
hkl¦. Rhombic system, space group Pbca, a = 18.0586(8), b = 19.9898(9), c = 20.5553(8) Å, V = 7420.2(6) Å3. The structure is based on {(UO2)3[(S,Cr)O4]5}4– anionic layers, formed by combination of UO7 pentagonal bipyramids and TO4 tetrahedra through common vertices. The { (UO2)3 [(S,Cr)O4]5}4– layers are parallel to the (010) plane. The Cu2+ (H2O)6 octahedra and additional water molecules are located in the interplanar space and provide binding of the layers in the structure by hydrogen bonds. Based on the occupancy of tetrahedral positions, more accurate chemical formula of the compound should be written as Cu2{(UO2)3[(S0.804 Cr0.196)O4]5} (H2O)17.Translated from Radiokhimiya, Vol. 46, No. 5, 2004, pp. 408–411.Original Russian Text Copyright © 2004 by Krivovichev, Burns. 相似文献
8.
V. A. Morozova S. F. Marenkin S. G. Mikhailov O. G. Koshelev 《Inorganic Materials》2005,41(3):212-216
The optical absorption, photoconductivity, and short-circuit photocurrent spectra of structurally perfect Cd1 - x
ZnxAs2 (x = 0.03, 0.05, 0.06) single crystals are studied for the first time near the intrinsic edge in the range 80–300 K. The results demonstrate that the intrinsic edge in the solid solutions is due to indirect transitions involving the formation of excitons for both the E c and E c polarizations. The indirect gaps
g
i
of the solid solutions are determined. In the range 80–300 K, the data for x = 0–0.06 and both polarizations are well fitted by
g
i
(x) =
g
i
(0) + 0.0866x + 2.35x
2. The introduction of 6 mol % ZnAs2 into CdAs2 increases its
g
i
by 14 meV.Translated from Neorganicheskie Materialy, Vol. 41, No. 3, 2005, pp. 268–272.Original Russian Text Copyright © 2005 by Morozova, Marenkin, Mikhailov, Koshelev.This revised version was published online in April 2005 with a corrected cover date.This revised version was published online in April 2005 with a corrected cover date. 相似文献
9.
SnO2/MoO3 nanocomposites are synthesized in a broad composition range through chemical precipitation from solution, and their phase composition and microstructure are investigated by x-ray diffraction. The gas sensitivity of the nanocomposites to lower alcohols (CnH2n + 1 OH, n=1–4) is studied by in situ conductance measurements. The results are interpreted in terms of the acid-base properties of the nanocomposite surface.__________Translated from Neorganicheskie Materialy, Vol. 41, No. 4, 2005, pp. 442–449.Original Russian Text Copyright © 2005 by Makeeva, Rumyantseva, Gaskov. 相似文献
10.
Low-temperature plasma synthesis was used to prepare solid solutions ( and ) in the ZnFe2O4–Zn2ZrO4pseudobinary system. The Zn2 – x
Zr1 – x
Fe2x
O4solid solutions were found to have a tetragonal spinel structure (a= 8.607–8.740 Å, c= 8.798–9.120 Å) in the composition range x= 0–0.55 and a cubic spinel structure (a= 8.447–8.539 Å) at x= 0.75–1.0. The tetragonal lattice distortion is attributed to a pseudo-Jahn–Teller effect. The electrical conductivity of the solid solutions shows semiconducting behavior and rises by a few orders of magnitude with increasing Fe3+content. 相似文献
11.
Soumen Pal A. K. Bandyopadhyay S. Mukherjee B. N. Samaddar P. G. Pal 《Bulletin of Materials Science》2011,34(4):865-872
Although low temperature fast coprecipitation technique has been used to synthesize stoichiometric (MgO-nAl2O3, n = 1) MgAl2O4 spinel forming precursor, delayed spinellization has always been the concern in this process. In this article, the precursor
of this ‘fast technique’ has been used for bulk production by further processing by high speed mixing with solvents and mechanical
activation by attrition milling in terms of superior spinellization. At 1000°C, MgAl2O4 — γ-Al2O3 solid solution and MgO phases are formed (spinel formed by 1000°C is regarded as primary spinel). At higher temperatures,
due to large agglomerate size, MgO can not properly interact with the exsolved α-Al2O3 from spinel solid solution to form secondary spinel; and consequently spinellization gets affected. Solvent treatment and
attrition milling of the coprecipitated precursor disintegrate the larger agglomerates into smaller size (effect is more in
attrition). Then MgO comes in proper contact with exsolved alumina, and therefore total spinel formation (primary + secondary)
is enhanced. Extent of spinellization, for processed calcined samples where some alumina exists as solid solution with spinel,
can be determined from the percentage conversion of MgO. Analysis of the processed powders suggests that the 4 h attrited
precursor is most effective in terms of nano size (< 25 nm) stoichiometric spinel crystallite formation at ≤ 1100°C. 相似文献
12.
The formation mechanisms of Li x Na1 ?x Ta y Nb1 ? y O3 perovskite solid solutions in the Li2CO3-Na2CO3-Nb2O5-Ta2O5 system have been studied by x-ray diffraction, differential thermal analysis, thermogravimetry, IR spectroscopy, and mass spectrometry at temperatures from 300 to 1100°C. The results indicate that the synthesis of Li x Na1 ? x Ta y Nb1 ? y O3 solid solutions involves a complex sequence of consecutive and parallel solid-state reactions. An optimized synthesis procedure for Li x Na1 ? x Ta y Nb1 ? y O3 solid solutions is proposed. 相似文献
13.
Microscopic and Macroscopic Magnetic Properties of the MgAl
x
Cr
x
Fe2 − 2x
O4 Spinel Ferrite System
To determine the influence of the substitution of Al3+ and Cr3+ for Fe3+ in MgFe2O4 ferrites on the structural and magnetic properties, the MgAl
x
Cr
x
Fe2 – 2x
O4 (x = 0.0–0.8) spinel systems were studied by using the X-ray diffraction analysis, magnetization in strong fields, magnetic susceptibility in weakly variable electric fields, and Mössbauer spectroscopy. Unlike previous investigations, it was discovered that a half of Al3+ occupies tetragonal positions. The system forms a noncollinear spin structure and a central paramagnetic doublet is superimposed over the magnetic sextet in the Mössbauer spectrum (0.5 > x > 0.2). The dependence of the magnetic susceptibility on temperature reveals the normal ferromagnetic properties of the material. 相似文献
14.
Jinghai Yang Jiang Du Jian Cao Maobin Wei Haifeng Niu Lili Yang Xiaoyan Liu Ming Gao 《Journal of Materials Science: Materials in Electronics》2018,29(2):876-880
In this paper, ZnS:Mn2+ quantum dots (QDs) Fe3O4 quantum dots (QDs)/SiO2 nanocomposites were successfully synthesized by reverse microemulsion method. The average diameter of ZnS:Mn2+ QDs, Fe3O4 QDs and ZnS:Mn2+ QDs Fe3O4 QDs/SiO2 nanocomposites was about 5.8, 9 and 29 nm, respectively. As the mass ratio of ZnS:Mn2+ to Fe3O4 QDs increased from 2.5:4 to 7.5:4, the intensity of the yellow–orange emission coming from Mn2+ ions was increased. The superparamagnetic property of ZnS:Mn2+ QDs Fe3O4 QDs/SiO2 nanocomposites was observed at room temperature, and the saturation magnetization was decreased as the amount of ZnS:Mn2+ QDs increased. 相似文献
15.
Biao Dong Hua Yang Lianxiang Yu Yuming Cui Weiqun Jin Shouhua Feng 《Journal of Materials Science》2007,42(13):5003-5006
Sm
x
BiY2–x
Fe5O12 (x = 0, 0.1, 0.2, 0.4, 0.6, 0.8) nanocrystals were fabricated by sol–gel method. Samples were characterized by powder X-ray
diffraction (XRD), thermal gravity analysis (TGA) and differential thermal analysis (DTA), transmission electron microscopy
(TEM), vibrating sample magnetometer(VSM). The samples were calcined at 850 °C and 1000 °C and the average size of the particles
were determined by Scherrer’s formula . In this paper, we discussed the effect of Sm3+ substitution for Y3+ on magnetic properties of BiY2Fe5O12. The magnetic properties of Sm
x
BiY2−x Fe5O12 are decreased with increasing content of Sm ion. 相似文献
16.
Seven samples of the system Cu1–xCdxFe2O4 were prepared by thermal decomposition of mixed metal oxalates with x = 0.0, 0.1, 0.3, 0.5, 0.7, 0.9 and 1.0. The formation of the ferrispinel was studied by XRD, FT-IR, Mössbauer spectroscopy, electrical conductivity and magnetic susceptibility measurements. XRD showed single cubic spinel phase for all the samples except for CuFe2O4 sample which shows a tetragonal structure. An increase in the lattice parameter of the ferrispinel was observed with increasing the cadmium content. The temperature variation of ac conductivity showed four definite regions with three transitions which attribute to the change in the conduction mechanism with increasing temperature. Magnetic properties of the sample with x 0.5 showed a decrease in the effective magnetic moment with the increase in the cadmium content which means that the ferromagnetics are widely separated and enclosed by non-magnetic cadmium ions. A well defined hyperfine Zeeman spectrum is observed for samples with x 0.3 at room temperature and resolved into two sextets corresponding to the octahedral and tetrahedral sites. The propable ionic configuration of the system proposed is (CdxCuyFe1–x–y)[Cu1–x–yFe1+x+y]O4. 相似文献
17.
Biao Dong Hua Yang Yuming Cui Lianxiang Yu Shouhua Feng 《Journal of Materials Science》2007,42(9):3167-3171
BiY2Cr x Fe5?x O12 (x = 0, 0.05, 0.1, 0.2, 0.3) nanocrystals were synthesized by using a sol-gel method. Samples were characterized by the powder X-ray diffraction (XRD), the thermal gravity analysis (TGA) and the differential thermal analysis (DTA), the vibrating sample magnetometer(VSM) and Mössbauer spectrums. The average sizes of the particles were determined by the Scherrer’s formula. The special Ms and Mössbauer spectra of BiY2Cr x Fe5?x O12 nanocrystals are researched at room temperature. It is seen that the special Mss of samples are initially increased with increasing Cr3+ content (x < 0.1), and decreased with increasing content of Cr3+ ions (x > 0.1). 相似文献
18.
New solid solutions, Bi2?x?y Tm x Nb y O3+δ, with tetragonal and cubic structures have been synthesized in the Bi2O3-Tm2O3-Nb2O5 system, and their electrical conductivity has been measured at temperatures from 670 to 1020 K. The 1020-K conductivity of the tetragonal solid solution Bi1.8Tm0.15Nb0.05O3+δ is comparable to that of Bi1.75Tm0.25O3, the best conductor in the Bi2O3-Tm2O3 system. 相似文献
19.
R. A. Grigoryan 《Inorganic Materials》2007,43(11):1247-1251
The multicomponent refractory oxide system Zn2(TiaSnb)1 ? x ZrxO4 (a + b = 1; a: b = 1: 5, 1: 4, 1: 3, 1: 2, 1: 1, 1: 0, 2: 1, 3: 1, 4: 1; x = 0?1.0; Δx = 0.05) has been studied by x-ray diffraction, using samples prepared by melting appropriate oxide mixtures in a low-temperature hydrogen-oxygen plasma. Two phases, both with wide homogeneity ranges, have been identified: α-phase, with a cubic inverse spinel structure, and β-phase, with a tetragonal spinel structure. The phase boundaries in the system have been determined. Structural data are presented for about 100 solid solutions of different compositions. 相似文献
20.
The real part of the dielectric constant () and the dielectric loss angle (tan ) as well as the ac conductivity of ferrite Mg1+x
Ti
x
Nd
y
Fe2–2x–y
O4 0.1 x 0.9 at fixed Nd concentration of 0.025 were measured at different temperatures as a function of frequencies. The variation of activation energy as a function of the applied frequency was reported. The obtained data were discussed on the basis of the valence exchange between (Fe3+, Fe2+), (Fe2+, Nd3+) and (Fe2+, Ti4+). Also the effect of sintering temperature and heating rate of preparation were discussed. 相似文献