共查询到20条相似文献,搜索用时 31 毫秒
1.
Polycrystalline samples La1.85Sr0.15Cu1–xZnxO4– (0 x 0.3), La1.85Sr0.15Cu1–xNixO4– (0 x 0.3), and La1.85Sr0.15Cu1–xMgxO4– (0 x 0.3) were synthesized by the solid-state reaction method. The crystal structure and phonon vibration were investigated by means of X-ray diffraction (XRD) and infrared spectrum. Zn, Ni, and Mg doping results in the lattice parameter c decreasing and a (b) increasing. The change of the phonon modes around 504 cm–1 and 681 cm–1 can be satisfactorily interpreted in terms of the change of the crystal structure and the itinerant nature of charge carrier in CuO2 sheet. The relation between the structure and phonon vibration is discussed. 相似文献
2.
M. B. Maple M. C. de Andrade J. Herrmann Y. Dalichaouch D. A. Gajewski C. L. Seaman R. Chau R. Movshovich M. C. Aronson R. Osborn 《Journal of Low Temperature Physics》1995,99(3-4):223-249
Experimental efforts to characterize and develop an understanding of non Fermi liquid (NFL) behavior at low temperature in f-electron materials are reviewed for three f-electron systems: M1–xUxPd3 (M = Sc, Y), U1–xThxPd2Al3, and UCu5–xPdx. The emerging systematics of NFL behavior in f-electron systems, based on the present sample of nearly ten f-electron systems, is updated. Many of the f-electron systems exhibit the following temperature dependences of the electrical resistivity p, specific heat C, and magnetic susceptibility for T T0, where To is a characteristic temperature: P(T) 1 –aT/T
0, where a < 0 or > 0, C(T)/T (-1/T
o) In (T/bT
0), and (T) 1 –c(T/To)1/2. In several of the f-electron systems, the characteristic temperature To can be identified with the Kondo temperature Tk. 相似文献
3.
We study the influence of microstructure of high-strength cast irons of ferritic, ferritic-pearlitic, and pearlitic classes on the characteristics of strength and cyclic crack resistance and establish the relationship between the characteristics of strength and cyclic crack resistance and the chemical composition and microstructural parameters of the matrix and graphite inclusions of high-strength cast irons. Indeed, the ultimate strength u = 750–850 MPa, fatigue threshold K
th = 8–10 MPa
, and cyclic fracture toughness K
fc = 50–60 MPa
are guaranteed by the pearlitic matrix and the following parameters of the graphite phase: the content of graphite f
p 10%, the degree of its spheroidization of about 95%, the size of globules d
gl 20–50 m, and the distance between them 40–70 m, obtained in high-strength cast irons containing (wt.%): 3.2–3.5 C, 1.9–2.5 Si, 0.35–0.4 Mn, and 0.05 Mg. 相似文献
4.
L. V. Kokhanovskii V. V. Vashuk O. P. Ol'shevskaya O. I. Kirilenko 《Inorganic Materials》2001,37(7):730-736
The oxygen stoichiometry of SrCo1 – x
Fe
x
O3 – (0.1 x 0.9) solid solutions was determined by solid-electrolyte coulometry as a function of temperature (20–1000°C) and oxygen partial pressure (1–100 Pa). The results, together with X-ray diffraction studies between 400 and 900°C, indicated a sequence of phase transitions: perovskite brownmillerite high-temperature perovskite. The composition stability region of the parent perovskite structure was shown to be 0.2 <x 1.0. The Co-rich samples (x 0.2) consisted of perovskite and hexagonal phases. 相似文献
5.
Nd1 – x
Ba
x
MnO3 ± (0.1 x 0.5) and R0.7Ba0.3MnO3 ± (R = La, Pr, Sm, Eu) solid solutions were prepared from nitrate mixtures by solid-state reactions in air and were characterized by x-ray diffraction and thermogravimetry. The oxygen content of the solid solutions was determined by iodometric titration. The materials were found to have a nearly perfect oxygen stoichiometry ( 0). As shown by pH measurements, the solid solutions have a high water resistance (extent of water degradation no larger than 0.1%). The dissociation of the Nd1 – x
Ba
x
MnO3 ± (0.2 x 0.4) solid solutions was studied as a function of temperature and oxygen partial pressure (–10 log(Po
2/Pa) 1.4) by a special TG technique. 相似文献
6.
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
7.
A method is suggested for the investigation of the thermodynamic properties of ternary liquid-metal alloys at high temperatures in the entire region of concentration triangle. The method is demonstrated for a Na–K–Cs ternary system. Data are obtained for the enthalpy and Gibbs energy of formation of alloy in the temperature range of 200 T 1200 K and concentration range of 0 x
i
(j, k) 1. The results reveal a very fine effect associated with the temperature rise, namely, the inversion of excess partial Gibbs energy G¯
i
*= RTln
i
(
i
is the activity coefficient of the liquid component) and the change of sign of deviation of partial pressure, as well as of total pressure, from the respective values in accordance with Raoult's law. The obtained results may be used to interpret the available literature data on independent measurements of the saturation pressure. 相似文献
8.
V. Ya. Chekhovskoi R. A. Belyaev Yu. V. Vavilov 《Journal of Engineering Physics and Thermophysics》1972,22(6):728-731
An apparatus is described for measuring the thermal conductivity and diffusivity on small specimens of solid materials; also the results are shown which have been obtained for refractive high-alumina concrete by such measurements.Notation
thermal conductivity at the mean temperature of specimens, W/m· °C
- Q
power of the central heater, W
- F
cross section area of a specimen, m2
- t1,2
temperature drop across the specimens, °C
-
1,
2
difference in heights between the thermocouple beads, center-to-center, in the first and in the second specimen respectively, m
- t
temperature, °C
-
time coordinate, min
- d1= (d1u+d1l
)/2
mean distance between specimen contact plane and nearest thermocouple beads, for the upper and lower specimen, m
- d2= (d2u+d2l
)/2
mean distance between specimen contact plane and farthest thermocouple beads, for the upper and lower specimen, m
- dt(d1,)/d
rate of temperature rise at section d1 of the specimen at time, °C/h
- t=t1+t2
sum of temperature drops in the specimens at time, °C
- m
heating rate, h–1
-
a
thermal diffusivity of specimens, referred to their mean temperature, m2/h
-
=m/a, m–1 b=¦(tu–tl)/tu¦
heating nonuniformity factor
Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 22, No. 6, pp. 1049–1054, June, 1972. 相似文献
9.
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
10.
Elastic-plastic two-dimensional (2D) and three-dimensional (3D) finite element models (FEM) are used to analyze the stress distributions ahead of notches of four-point bending (4PB) and three-point bending (3PB) specimens with various sizes of a C-Mn steel. By accurately measuring the location of the cleavage initiation sites, the local cleavage fracture stress f and the macroscopic cleavage fracture stress F is accurately measured. The f and F measured by 2D FEM are higher than that by 3D FEM. f values are lower than the F, and the f values could be predicted by f=(0.8––1.0)F. With increasing specimen sizes (W,B and a) and specimen widths (B) and changing loading methods (4PB and 3PB), the fracture load P
f changes considerably, but the F and f remain nearly constant. The stable lower boundary F and f values could be obtained by using notched specimens with sizes larger than the Griffiths–Owen specimen. The local cleavage fracture stress f could be accurately used in the analysis of fracture micromechanism, and to characterize intrinsic toughness of steel. The macroscopic cleavage fracture stress F is suggested to be a potential engineering parameter which can be used to assess fracture toughness of steel and to design engineering structure. 相似文献
11.
D. P. Gosain T. Shimizu M. Ohmura M. Suzuki T. Bando S. Okano 《Journal of Materials Science》1991,26(12):3271-3274
Composition dependence of properties of Sb2Te3–x
Se
x
in the range 0x<3 were studied using differential thermal analysis and X-ray diffraction. Sb2Te3–x
Se
x
form solid solution for 0<x1.25 and 2.75x<3. A systematic study of crystallization temperature in Sb2Te3–x
Se
x
(0x2.75) thin films prepared by flash evaporation was carried out. In preliminary experiments for some compositions, more than 103 repetitions between amorphous and crystalline states were attained by the application of electric pulses. 相似文献
12.
The Gibbs' energies of formation of BaCuO2, Y2Cu2O5 and Y2BaCuO5 from component oxides have been measured using solid state galvanic cells incorporating CaF2 as the solid electrolyte under pure oxygen at a pressure of 1.01×105 Pa BaO + CuO BaCuO2 G
f,ox
o
(± 0.3) (kJ mol–1)=–63.4–0.0525T(K) Y2O3 + 2CuO Y2Cu2O2 G
f,ox
o
(± 0.3) (kJ mol–1)=18.47–0.0219T(K) Y2O3 + BaO + CuO Y2BaCuO5 G
f,ox
o
(± 0.7) (kJ mol–1)=–72.5–0.0793T(K) Because the superconducting compound YBa2Cu3O7– coexists with any two of the phases CuO, BaCuO2 and Y2BaCuO5, the data on BaCuO2 and Y2BaCuO5 obtained in this study provide the basis for the evaluation of the Gibbs' energy of formation of the 1-2-3 compound at high temperatures. 相似文献
13.
The Ge1–x
Sn
x
Se2.5 system was prepared by melting the correct ratio of high purity elements in quartz evacuated ampoules followed by quenching in ice. It was found that, within the Ge1–x
Sn
x
Se2.5 system, a glassy state can be formed when 0 x 0.4. On increasing x to 0.6 a glassy state could not be obtained, as is confirmed by X-ray diffraction. Differential thermal analysis (DTA) was carried out to study the effect of composition on the stability of amorphous phase. Ge1–x
Sn
x
Se2.5 (where 0 x 0.6) thin films have been prepared by the thermal evaporation technique. The electrical conductivity of the thin films have been studied as a function of composition and film thickness. 相似文献
14.
A. G. Belous O. N. Gavrilenko E. V. Pashkova K. P. Danil'chenko O. I. V'yunov 《Inorganic Materials》2004,40(8):867-873
The effects of the nominal composition and synthesis conditions on the lithium nonstoichiometry of La2/3 – x
Li3x
4/3 – 2x
Nb2O6 (I) and La2/3 – x
Li3x
4/3 – 2x
Ta2O6 (II) solid solutions are studied. The results demonstrate that lithium losses can be reduced from 26–30 to 14–15 mol % in system I and from 15 to 4 mol % in system II. It is shown that the disturbance of electroneutrality caused by Li nonstoichiometry in the solid solutions is eliminated via the formation of oxygen vacancies in positions O(1) (1f: 1/2 1/2 0) and O(2) (1h: 1/2 1/2 1/2) of the cation-deficient perovskite structure. The optimal lithium ion conductivity is offered by solid solutions with /3x 2.6 and x 0.136–0.143. 相似文献
15.
N. Balchev K. Nenkov B. Kunev A. Souleva Ts. Tsacheva S. Hoste 《Journal of Superconductivity》2001,14(6):713-717
The effect of Sn doping in (Pb0.6Sn
y
Cu0.4 – y
)Sr2(Y1 – x
Ca
x
)Cu2O
z
with 0 y 0.3 and 0 x 0.7 was investigated. It was established that a nearly pure 1212 phase can be obtained at 0 y 0.1 and 0 x 0.3. The obtained XRD patterns as well as the results of the EDX and ICP-AES analyses showed that Sn substitution is possible in the (Pb,Cu)-1212 phase. Superconductivity was observed at 0.4 x 0.7. The onset of the diamagnetic transitions varied from 10 to 30 K. The influence of the strong Pb deficiency on the superconducting properties of the samples was discussed. 相似文献
16.
V. I. Sokurenko V. K. Shcherbakov Yu. P. Shcherbakov 《Journal of Engineering Physics and Thermophysics》1972,22(6):750-755
A method is shown and formulas are derived by which local angular radiation coefficients can be determined in certain two-body systems where the configuration is arbitrary but one of the bodies is either a cylinder or a rectangular plate.Notation int
radiation vector of body 1
-
E
int
intrinsic radiation intensity of body 1
-
x,
y,
z
components of the geometrical radiation vector along rectangular coordinates
- r0=x2+z2
shortest distance from point M(x, y, z) to linear radiator
-
0
,
0
'
angles subtending the two segments of the linear radiator from point M(x, y, z) on area element 2 of irradiated surface
-
l
length of the cylinders
- x, y, z
space coordinates of point M
Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 22, No. 6, pp. 1080–1088, June, 1972. 相似文献
17.
The manner in which oxygen is incorporated into YBa2Cu3O
x
(YBCO) at 800°C for values ofx close to 6 is shown to be in the form of neutral oxygen interstitials, O
i
x
. The experimental data on which this conclusion is based are obtained from measurements of oxygen partial pressure,P(O2), as a function of compositionx and temperatureT (5.99x 6.35, 825T1120 K). The data are obtained by a solid-state electrochemical method. Other conclusions of this study include: (a) O
i
x
are noninteracting forx 6. (b) The stoichiometric composition of YBCO isx 6.0. (c) The reaction enthalpy of oxidation is 179 kJ/mol O2. (d) The Fermi level changes by –0.2 eV asx increases from 6.05 to 6.35. 相似文献
18.
V. L. Volkov G. S. Zakharova L. V. Kristallov M. V. Kuznetsov G. Dai M. Tong 《Inorganic Materials》2001,37(4):408-412
Powders and films of (NH4)2 – x
H
x
V12 – y
Mo
y
O31 ± · nH2O (0 x 2, 0 y 3) xerogels with a layered structure were prepared for the first time. According to IR spectroscopy data, the V–O–Mo layers in the xerogels are similar to those in the delta vanadium bronze (NH4)0.5V2O5. X-ray photoelectron spectroscopy shows that the vanadium and molybdenum in the xerogels are mainly in the oxidation states 5+ and 6+, respectively. The materials also contain small amounts of V4+and OH–. The thermal stability of the materials increases with Mo content. The electrical conductivity of the films depends on air humidity and reaches a maximum at the composition (NH4)1.5H0.5V9Mo3O31 + · nH2O. At temperatures in the range 20–70°C and air humidity between 12 and 59%, the activation energy of conduction is very low. 相似文献
19.
Our previous theory yielded for the Zeeman splitting of the imaginaryJ=1 collective mode in3He-B the result =2+0.25J
z
( is the effective Larmor frequency). In this paper we take into account the downward shift of the pair-breaking edge from 2 to 22– (2 and 1 are the longitudinal and transverse gap parameters). This leads to a complex Landé factor: the frequencies of theJ
z
=±1 components become =2+0.39J
z
, and the linewidths of these resonances become finite: =0.18. The coupling amplitudes of theJ
z
=±1 components to density are found to be proportional to gap distortion, (1–2/(/)2. Our results for the ultrasonic attenuation due to theJ
z
=±1,J=1 modes are capable of explaining the field dependence of the attenuation close to the pair-breaking edge as observed by Dobbs, Saunders, et al. The observed peak is caused by theJ
z
=–1 component: its height increases due to gap distortion as the field is increased, and the peak shifts downward in temperature and its width increases with the field due to the complex Landé factor. TheJ
z
=+1 component gives rise to a corresponding dip relative to the continuum attenuation. 相似文献
20.
We report on the first investigation of the effect of magnetic dilution on nuclear magnetic spin interactions in metals; we studied this effect in the diluted Van Vleck paramagnets Pr1–xYxNi5. In addition, we investigated the electronic magnetic properties of these intermetallic compounds. For this purpose, we have measured the nuclear and electronic susceptibilities of Pr1–xYxNi5 with x = 0 to 0.2 at 50K T 8 mK and at 2.2 K T 300 K. We observe a linear decrease of the electronic Van Vleck susceptibility and of the hyperfine enhancement factor by 13% (per mole Pr3+). The hyperfine-enhanced nuclear susceptibility decreases by about a factor of three when going fromx = 0 tox = 0.2. The samples show nuclear ferromagnetic transitions of141Pr with nuclear Curie temperatures Tc decreasing from 370 K to 100 K and Weiss temperatures decreasing from 218 K to 13 K in this concentration range. These data are compared with the results of mean-field calculations. In addition, we report on measurements of the nuclear spin relaxation time of these compounds, for which we find values of a few msec at millikelvin temperatures and a critical speeding-up at Tc. Our data give hints that for x > 0.2 the character of the nuclear magnetic transition may change, possibly to a nuclear spin glass freezing. 相似文献