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1.
The chemical control of underdoped and overdoped states in the Y(Ba2 – y
Sr
y
)Cu3O6 + (0.1 and 0.9) compounds has been observed by high-resolution O K-edge X-ray-absorption near-edge-structure spectra. The chemical substitution of Sr for Ba in the fully-oxygenated Y(Ba2–y
Sr
y
)Cu3O6 + (0.9) compounds gives rise to high hole concentrations within both the CuO2 planes and the out-of-plane sites, leading to the overdoped state and the decrease in the superconducting transition temperature from 92 K for y=0 to 84 K for y=0.8. In contrast, an increase in the Sr content in the oxygen-deficient Y(Ba2 – y
Sr
y
)Cu3O6 + (0.1) compounds did not indicate superconductivity. The oxygen-deficient compounds exhibit the underdoped state due to the low hole concentration. 相似文献
2.
The phase relations in the composition region SrFeO3 – –Fe2O3–BiFeO3 are studied in air by x-ray diffraction and electron microscopy. The 1000°C phase compatibility diagram is constructed. Sr1 – x
Bi
x
FeO3 – solid solutions are prepared in the range 0 < x 0.8. Their lattice parameter is found to vary nonlinearly with x. Two new phases were identified: (Sr,Bi)3Fe4O
y
(tetragonal lattice, a= 3.907(2) Å, c= 27.30(2) Å) and Sr0.6Bi0.4FeO3 – (tetragonal lattice,a = 5.555(2) Å, c= 11.848(5) Å). 相似文献
3.
J. Yuenyongchaiwat S. Tantayanon Jidong Lou Yi Hua Ma 《Journal of Materials Science》2004,39(23):7067-7074
Fine particle strontium and iron substituted lanthanum gallates La1–x
Sr
x
Ga1–y
Fe
y
O3–, where x = 0.2, 0.4, and 0.6; y = 0.2, 0.4, 0.6, and 0.8, have been synthesized by a modified citrate method. The formation of these powders was confirmed by the X-ray powder diffraction (XRD) and the fine particle of La0.6Sr0.4Ga0.2Fe0.8O3– was investigated by scanning electron microscopy (SEM), and particle size analysis. The single phase of La0.8Sr0.2Ga0.4Fe0.6O3–, La0.6Sr0.4Ga0.2Fe0.8O3–, and La0.4Sr0.6Ga0.2Fe0.8O3– powders could be obtained both with and without calcination. The amount of the secondary phase increased when the amount of Sr in La1–x
Sr
x
Fe0.6Ga0.4O3– was more than 0.2 (x > 0.2) and the amount of Fe in La0.6Sr0.4Ga1–y
Fe
y
O3– and La0.4Sr0.6Ga0.2Fe0.8O3– was less than 0.8 (y < 0.8). The results indicated that in the pH range of 1.36–9.27, the single phase of La0.6Sr0.4Ga0.2Fe0.8O3– was formed without calcination and the pH had negligible effects on the structure and lattice parameter. The fine particle of these calcined powders (<4 m) was obtained with the average particle size 1.70 m at pH = 1.36 and with the average particle size between 0.56–0.60 m at pH range between 3.39–9.27, and with a lattice parameter about 3.9 Å. 相似文献
4.
D. D. Khalyavin A. P. Sazonov I. O. Troyanchuk R. Szymczak H. Szymczak 《Inorganic Materials》2003,39(10):1092-1096
Data are presented on the structural and magnetic properties of Ln1 – x
Ba
x
CoO3 – (Ln = Nd, Sm; 0 < x 0.66) samples slowly cooled in air after synthesis. The composition stability limits of the intermediate phases Ln1 – y
Ba1 + y
Co2O5 + and solid solutions are determined. The magnetic phase diagram of the Nd1 – x
Ba
x
CoO3 – system is constructed. 相似文献
5.
J. P. Zhou J. -S. Zhou J. B. Goodenoug J. T. McDevitt 《Journal of Superconductivity》1995,8(5):651-652
The metallic conductivity of both the CuO2 sheets and the CuOx chains of YBa2Cu3O7– has been established. We have used double doping in (Y1–xCax)(Ba2–xLax)Cu3O7– to destroy the integrity of the CuO1– chains while keeping constant the total oxidation state of the Cu-O array. A break-up of the chain segments allows us to establish the temperature dependence of the Seebeck coefficient, (T), due to the CuO2 sheets and, by difference, that of the CuO1– chains in YBa2Cu3O7–. We also show that double doping enhances significantly the chemical stability of the superconductive phase. The origin of the chemical stability and of the behavior of (T) is interpreted. 相似文献
6.
Phase equilibria in the LaCoO3—SrCoO2.5—SrNiO3—LaNiO3 system are studied at 1100°C in air using samples prepared by standard solid-state reactions and by the citrate route. The composition region and structure of La1 – xSrxCo1 – yNiyO3 – solid solutions are determined by x-ray powder diffraction. The structure is refined by the Rietveld profile analysis method with Fullprof 2002. The solid solutions with 0< x 0.5 have a rhombohedrally distorted perovskite structure (sp. gr.R
c). The rhombohedral distortion decreases with increasing Sr content, and the solid solutions with x > 0.5 have an ideal cubic structure (sp. gr. Pm3m). The composition dependences of lattice parameters for the La1 – xSrxCo1 – yNiyO3 – solid solutions are presented.Translated from Neorganicheskie Materialy, Vol. 40, No. 12, 2004, pp. 1520–1525.Original Russian Text Copyright © 2004 by Aksenova, Gavrilova, Cherepanov. 相似文献
7.
The microstructures of mixed-conducting Sr4Fe6O13±, and Sr3.6La0.4Fe6O
z
(nominal composition) have been studied by electron microscopy. The lanthanum free material shows a microstructure containing mainly Sr4Fe6O13±, with some 5 vol% Sr1–y
La
y
Fe12O19embedded as micron-size inclusions. The lanthanum-containing material revealed a significantly different microstructure consisting of 20 vol% micron-size Sr1–y
La
y
Fe12O19embedded in 40 vol% (Sr0.85La0.15)FeO3–tetragonal perovskite, and 40 vol% of plate-shaped nano-scale intergrowths between (Sr1–x
La
x
)FeO3–and Sr4Fe6O13±phases. Domains with dimensions of 20–50 nm are observed in the tetragonal perovskite when viewed along its fourfold axis. From compositional analysis it is concluded that there is little or no solubility of La in the Sr4Fe6O13±phase. The observed microstructure is important input in explaining the significant effect of La addition on the transport properties of Sr4Fe6O13±materials. 相似文献
8.
The phase composition, structure, and 920-K electrical conductivity of LiMn
x
Fe1 – x
O2(0 < x 1) and Li1 – y
Mn
y
FeO2 + (0 < y 1) materials prepared by solid-state reactions in air at 1270 K were studied before and after soaking in molten (Li0.62K0.38)2CO3. The highest conductivity of 32 S/m was found in the spinel solid solution Li0.2Mn0.8FeO2 + ( = 2/3). Soaking in the carbonate melt converted all Li1 – y
Mn
y
FeO2 + samples into rocksalt solid solutions and reduced their conductivity. 相似文献
9.
The lattice parameters and composition range of orthorhombic CaTi1 – x
CrxO3 – solid solutions were determined by x-ray powder diffraction. Samples with the nominal compositions CaTi1 – y
InyO3 – , synthesized in the range y=0.05–0.3, consisted of two phases: CaTiO3 – and a CaIn2O4-based phase. The compositions of the synthesized phases were checked by x-ray microanalysis. The electrical conductivity of the CaTi1 – x
CrxO3 – (0 < × 0.2)solid solutions was measured as a function of oxygen partial pressure (0.21 × 104 to 1.0 × 10–11 Pa) at 900 and 1000°C. Cr doping of calcium titanate was shown to increase its conductivity. A mechanism of defect formation in doped calcium titanate was inferred from conductivity versus
data.__________Translated from Neorganicheskie Materialy, Vol. 41, No. 4, 2005, pp. 475–478.Original Russian Text Copyright © 2005 by Murashkina, Demina. 相似文献
10.
The mixed solid N
2–Ar has been studied at high pressure at the nitrogen–rich side of the phase diagram by Raman spectroscopy. The argon atoms dissolve into some of the nitrogen structures. Within the *–phase the Ar–-atoms are mainly located at the sphere–like disordered sites in agreement with computer simulations. The second order transition of pure N
2
is still present in the mixed solid at 25 mole% Ar. The * – * and *–fluid transitions in the mixed solid are shifted compared to the pure system. The phase diagram of the mixture for x[N
2]0.75 has been studied. 相似文献
11.
Phases, microstructures and properties of lead-zirconate-titanate (PZT) ceramics with the compositions Pb(Zr0.535– Ce Ti0.465) O3 where =0.0, 0.001, 0.01, 0.02 and 0.05 were studied. Rhombohedral and tetragonal phases were present at =0.0. The amount of the rhombohedral phase increased with increasing , and only the tetragonal phase was present for >0.001. Thec/a ratio of the tetragonal phase also increases with increasing . Particles of CeO2 were found to be present in compositions with >0.01, indicating that the solubility of CeO2 is less than 1a/o on the metals basis. The piezoelectric and electromechanical constants achieved maximum values for =0.001. The hardness increased monotonically with increasing . The modulus of rupture and the fracture toughness, however, went through a minimum and both stayed lower than their values for =0. 相似文献
12.
S. I. Vecherskii M. A. Konopel'ko N. O. Esina N. N. Batalov 《Inorganic Materials》2002,38(12):1270-1276
Data are presented on the temperature-dependent electrical conductivity and thermoelectric power of Ca1 – x
MnO3 – + xCeO2 (0 < x 0.15) mixtures obtained as intermediate products in the synthesis of Ca1 – x
Ce
x
MnO3 – solid solutions. The electrical properties of the mixtures are shown to be dominated by those of the perovskite-like phase Ca1 – x
MnO3 – and to depend on Ca concentration. All of the samples with 0 x 0.15 exhibit n-type conductivity. The charge transport in CaMnO3 – below 930 K is attributable to small-polaron hopping. At higher temperatures, conduction through delocalized states seems to prevail. In the Ca1 – x
MnO3 – + xCeO2 mixtures with 0.05 x 0.15, small-polaron hopping is observed between 160 and 920 K. Below 160 K, the temperature variation of conductivity in the samples with x = 0.1 and 0.15 follows Mott's law. 相似文献
13.
We performed Raman measurements at 18 K and pressures up to 25 GPa in order to construct a tentative phase diagram of the (N
2)1–x
:(O
2)x
–system at low temperatures. We varied the composition of the mixed system over the whole concentration range. Here we focused on the systems with high nitrogen concentration and pressures above 2 GPa. It is known that at room temperature oxygen is highly solvable in the –phase of N
2. The experimental results show that oxygen suppresses the disorder–order transition –N
2. 相似文献
14.
D. A. Bonn Kuan Zhang Ruixing Liang D. J. Baar D. C. Morgan W. N. Hardy 《Journal of Superconductivity》1993,6(4):219-225
The surface resistance of YBa2(Cu1–x
Zn
x
)3O7– has been measured in single crystals with oxygen vacancies ranging from=0.03 to 0.15 and for Zn impurity concentrations ofx=0, 0.0015 and 0.0031. Oxygen vacancies in the CuO chains have little influence on the microwave loss untilT
c
is reduced substantially. However, Zn impurities in the CuO2 plane sites drasticallydecrease the surface resistance, showing that the CuO2 plane conductivity dominates any CuO chain contribution to the microwave properties of YBa2Cu3O7–. The reduced microwave loss in the Zn-doped samples mimics the loss observed in state-of-the-art films and indicates that defects must be present in order to achieve the low microwave loss observed in some films. This sensitivity to low levels of defects is a consequence of the rapid increase in the scattering time in YBa2Cu3O7– belowT
c
. 相似文献
15.
Kyun Nahm Jung Soo Kim Kyeong Bock Lee Deoug Wha Shong Bo Young Cha Chul Koo Kim 《Journal of Materials Science》1990,25(3):1762-1764
Polycrystalline samples of the superconducting oxides (Y1–x
RE
x
)Ba2Cu3O7– (RE = Er and Dy) withx=0, 0.2, 0.4, 0.6, 0.8 and 1.0 were prepared. From the X-ray diffraction and the electrical resistivity measurements, it was found thatT
c and the unit cell volume have common peaks nearx0.4. Close examination of previously published data on the (Y1–xRE
x
)Ba2Cu3O7– system also indicate that an anomaly exists nearx–0.4. This anomaly is ascribed to an anomalous change of in oxygen nearx0.4. 相似文献
16.
N. V. Proskurina V. A. Cherepanov O. S. Golynets V. I. Voronin 《Inorganic Materials》2004,40(9):955-959
Phase equilibria in the La–Co–Fe–O system are studied at 1100°C in air using samples prepared by the citrate, nitrate, and conventional ceramic routes. The stability regions and structures of solid solutions in the La–Co–Fe–O system are determined by x-ray powder diffraction: LaCo1 – y
Fe
y
O3 – (0 < y 0.25, sp. gr. R
c; 0.775 y< 1, sp. gr. Pbnm), Co1 – y
Fe
y
O (0 < y 0.13, NaCl-type structure, sp. gr. Fm3m), and Fe3 – x
Co
x
O4 (0.84 x 1.38, sp. gr. Fd3m). The structural parameters of phase-pure solid solutions are determined by the Rietveld method. The composition dependences of lattice parameters are presented for LaCo1 – y
Fe
y
O3 – (0 < y 0.25) and Fe3 – x
Co
x
O4 (0.84 x 1.38). The 1100°C isotherm of the pseudoternary system La2O3–CoO–Fe2O3 in air is constructed. 相似文献
17.
T. Yu. Glavatskikh N. U. Venskovskii G. M. Kaleva A. V. Mosunov E. D. Politova S. Yu. Stefanovich 《Inorganic Materials》2001,37(6):647-650
Oxide-ion-conducting perovskite ceramics (La1 – y
Sr
y
)(Ga1 – x
Mg
x
)O3 – were prepared using hydrated Mg and La salts as starting reagents. X-ray diffraction and IR spectroscopy data demonstrate that the symmetry of the solid solutions changes in the sequence orthorhombic–rhombohedral–cubic with increasing Sr + Mg content. 相似文献
18.
M. Klauda J. Markl C. Fink P. Lunz G. Saemann-Ischenko F. Rau K. -J. Range 《Journal of Superconductivity》1994,7(2):485-487
We present investigations on the electronic structure of the recently discovered, electron-doped infinite-layer compound Sr1–xNdxCuO2–
(T
c40K) by means of photoelectron spectroscopy with synchrotron radiation. This system is compared with the two closely related cuprates Nd2–xCexCuO4–
(electron doped) and Nd1.4Ce0.2Sr0.4CuO4–
(hole doped). Valence band spectra in the Cu 3p3d resonance are interpreted in terms of CuO4 (n-doped compounds) and CuO5 (p-doped system) cluster models. From our calculations we find a considerably higher Cu3d Coulomb correlation for the electron-doped compounds as well as a very low Cu-O hybridization for the infinite-layer system. Partial Nd spectra of Sr0.85Nd0.15CuO2–
show the Nd dopants to be trivalent, thus confirming the infinite-layer compound to be electron doped. Analysis of partial Nd valence bands and magnetic susceptibilities of Nd2–xCexCuO4–
and Nd1.4Ce0.2Sr0.4CuO4–
gives very similar electronic parameters and antiferromagnetic correlations between Nd spins for both cuprates.We gratefully acknowledge financial support from the Bayerischer Forschungsverbund Hoch-temperatur-Supraleiter (FORSUPRA). 相似文献
19.
The thermal expansion, thermal stability, and electrical resistivity of the Ba1 – x
M
x
Pb1 + y
O3 + (M = Sr, Ca; 0 x 1.0, 0 y 0.2) and Ba1 – x
M"
x
Pb1 – y
M"
y
O3 + (M" = K, La; M" = Sc, Sb; x, y= 0.01) ceramic materials were studied between 293 and 1073 K in air. The linear thermal expansion coefficient of the ceramics was found to increase abruptly at 700 K, from (10–14) × 10–6K–1in the range 300–600 K to (13–18) × 10–6K–1in the range 800–1000 K. The electrical resistivity of the ceramics passes through a sharp maximum near 750 K, with the largest jump in resistivity at the compositions Ba0.6Sr0.4PbO3and Ba0.9Ca0.1PbO3. The anomaly in thermal expansion is likely associated with the rearrangement of the lead–oxygen polyhedra in the structure of the solid solutions, and the jump in resistivity is attributable to changes in the average oxidation state of Pb ions in the surface layer of the ceramics. 相似文献
20.
Shih-Chi Chu 《Journal of Engineering Mathematics》1970,4(1):65-76
Summary An efficient numerical method, used previously for linear differential equations [1], is here extended to systems of nonlinear ordinary differential equations. Spline functions are used as the basic approximations. Residuals are liquidated by setting their integrals equal to zero over specified subintervals of the intervals of analyticity. Several diverse examples are given.Notation
a
Radius of circular membrane
- [C
j
]
An unsymmetrical 4×4 matrix, defined by Eq. (6)
- [C
j
]
An unsymmetrical 6×6 matrix, defined by Eq. (8)
-
E
Young's modulus
-
F
i
Algebraic or transcendental functions
-
L
Differential operator
-
R
Closed interval
-
T
Dimensionless radius stress for the circular membrane
- [Y
j
]
The transpose of the row matrix [y
j
–1,y
j
–1,y
j
,y
j
]
- [Y
j
]
The transpose of the row matrix [y
j
–1,y
j
–1,y
j–1
,y
j
,y
j
,y
j
]
-
Residual
-
Poisson's ratio
Formerly with Department of Theoretical and Applied Mechanics, University of Illinois, Urbana, Illinois, USA. 相似文献