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1.
A differential thermal analysis in vacuum and studies of the coefficients of electrical conductivity and thermal conductivity,
and of the thermal emf are made in Ag2Te in the neighborhood of the structural phase transition. It is shown that these data can be used to calculate the switching
factor L(T), determine the region in which the phases coexist within the transition, and calculate the thermodynamic parameters. Prior
to and after the main phase transition, additional displacement transitions are observed. It is found that the phase transition
takes place roughly according to the scheme α
385 K→α′405 K→β′420 K→β
440 K. The specific heat C
p, changes in entropy ΔS and transition enthalpy ΔH, as well as the minimum phase fluctuation volume V, and the heat Q of the phase transition are determined. It is shown that excesses of Te and Ag have almost no effect on the transition temperatures
T
0, but have a substantial effect on the thermodynamic parameters.
Fiz. Tverd. Tela (St. Petersburg) 40, 1693–1697 (September 1998) 相似文献
2.
Bipin Singh Koranga P. Gaira Vinod Kumar 《International Journal of Theoretical Physics》2011,50(2):413-417
We study the Planck scale effects in the neutrino sector on the asymmetry between T-conjugate oscillation probabilities. ΔP
T
=P(ν
α
→ν
β
)−P(ν
β
→ν
α
), in a three flavor neutrino mixing. In this paper, we discuss some aspect of T violation effects in three flavor neutrino
oscillation. 相似文献
3.
M. V. Gorev E. V. Bogdanov I. N. Flerov A. G. Kocharova N. M. Laptash 《Physics of the Solid State》2010,52(1):167-175
The thermal expansion along the principal crystallographic axes of the (NH4)2WO2F4 and (NH4)2MoO2F4 oxyfluorides has been studied. The anomalous behavior of α
i
(T) due to the phase transitions has been revealed at T
1 = 271.4 K and T
2 ≈ 180 K for the molybdate and at T
1 = 201.5 K and T
2 ≈ 161 K for the tungstate. The quantities dT/dp and dT/dσ
i
, which characterize the dependence of the phase transition temperatures on the hydrostatic and uniaxial pressures, have been
determined from analyzing the results of studies of the thermal expansion and heat capacity with the use of the Pippard relations.
The p-T and α
i
-T phase diagrams reflect different characters of the influence of the pressure on the stability of the initial and distorted
phases of the oxyfluorides. The magnitudes of the extensive and intensive barocaloric effects determined in the vicinity of
the structural phase transitions are as follows: ΔS
BCE varies from approximately −10 to −17 J/mol K and ΔT
AD ≈ 8−17 K for the molybdate and ΔS
BCE varies from approximately −10 to −17 J/mol K and ΔT
AD ≈ 8−13 K for the tungstate. 相似文献
4.
High pressure Raman spectroscopic studies on Gd2(MoO4)3(GMO) have been carried out at ambient temperature in the diamond cell to 10 GPa hydrostatic pressure. These experiments have
revealed pressure-induced phase transitions in GMO near 2 GPa and 6.0 GPa. The first transition is from Pba2(β′) phase to another undetermined crystalline phase, designated as phase II, and the second transition is to an amorphized
state. On releasing pressure there is a partial reversion to the crystalline state. The Raman data indicate that the amorphization
is due to disordering of the MoO4 tetrahedral units. Further, it is inferred from the nature of the Raman bands in the amorphized material that the Mo-O bond
lengths and bond angles have a range of values, instead of a few set values. The results of the present study as well as previous
high pressure-high temperature quenching experiments strongly support that pressure-induced amorphization in GMO is a consequence
of the kinetically impededβ toα phase transition. The system in frustration becomes disordered. The rare earth trimolybdates crystallizing in theβ′ structure are all expected to undergo similar pressure-induced amorphization. 相似文献
5.
Rault J 《The European physical journal. E, Soft matter》2012,35(4):26
The thermodynamical and mechanical properties of (fragile and strong) glass are modeled based on a generalised activation
energy relationship log
τ
= ΔG
β
/RTn(T′) process of glass-forming liquids. This cooperative process involves 1/n(T′) elementary β motions of activation Gibbs energy ΔG
β
dependent on the equivalent temperature T′, the temperature of the liquid in equilibrium having the volume of the glass, function of temperature and aging conditions.
From this modified VFT law the relaxation of any properties (V , H , stress, creep) can be calculated and approximated by the Kohlrausch function. This model predicts consistency relationships
for: a) the temperature (and aging time) variation of the Kohlrausch exponent; b) the temperature dependence of the stabilisation
time domain of strong and fragile glass; c) the linear relation between the activation parameters (E
* energy, S
* entropy, V
* volume) of the α and β transition. The Lawson and Keyes (LK) relations are recalled and it is shown that these relations (somewhat equivalant to
the compensation law or Meyer-Neldel rule) are observed generally in glass. Morever the (macroscopic) ratios ΔH/ΔV observed during aging or after a temperature jump and the (microscopic) ratio E
*/V
* are found equal to κγ (κ compressibily, γ Grüneisen parameter), in agreement with the LK predictions. From various experiments and in agreement with predictions of
this model we conclude that the Grüneisen parameter γ
B
(pressure derivative of the bulk modulus) and the Mean Square Displacement (MSD) characterising the anharmonicity of solids
(and liquids) are the main parameters which govern the relaxation properties of the glass state. Linear relations between
the parameters γ
B
, the fragility m, and the Kohlrausch exponent n
g
at T
g
are explained. These correlations underscore a strong relationship between the fragilty of glass formers and the extent of
the anharmonicity in the interatomic interactions. 相似文献
6.
Measurements of the coefficient of linear thermal expansion α have been carried out for the orthorhombic and tetragonal phases
of RE1Ba2Cu3O
y
(RE=Y, Gd, Dy) compounds using a high resolution capacitance dilatometer in the temperature range 77–300 K. All the superconducting
samples exhibit a jump Δα at their respective transition temperatures,T
c. Evidences of, sample-to-sample variation in α values and dependence of Δα on the sample preparation conditions, have been
obtained. The non-superconducting samples, in general, exhibit lower values of α possibly because of lowering of oxygen content. 相似文献
7.
Yu. A. Simonov 《JETP Letters》2008,87(3):121-123
The dipion spectrum for the ϒ(nS) → ϒ(n′S) transition with n < 4 has the form dw/dq ∼ (phase space) |η − x|2, with x = q
2 − 4m
π2 / (ΔM)2 − 4m
π2 < q
2 ≡ M
ππ2, and ΔM = M(nS) − M(n′S). The parameter η is calculated and the spectrum is shown to reproduce the experimental data for all three types of decays:
3 → 1, 2 → 1, and 3 → 2 with η ≈ 0.5, 0, and −3, respectively.
The text was submitted by the author in English. 相似文献
8.
Polarization-optical studies and measurements of the birefringence Δn and the angle of rotation of the optical indicatrix for the (NH4)2NbOF5 crystal have been carried out in the temperature range 100–350 K. Two anomalies of the birefringence have been revealed at
the temperatures T
01 = 258 K and T
02 ≈ 219 K. According to the twinning pattern, the crystal undergoes successive changes in symmetry: orthorhombic ↔ monoclinic
1 ↔ monoclinic 2. The twofold axis of the monoclinic phases (or the normal to the plane) is directed along [001]or. The effect of the uniaxial compression along [011]or and the electric field E ≈ 25 kV/cm along [100]or on the twin structure has been studied. The ferroelastic phase transition at T
01 is due to the appearance of the shear deformation x
4(T) and is accompanied by significant anomalies of the birefringence. Strong pretransition phenomena mask the jumps in the birefringence
Δn(T) and in the angle of rotation of the indicatrix φ(T) at T
01. 相似文献
9.
The rapid solidification of Al-30%Cu-18%Ag ternary alloy is investigated by using the free fall method. Its solidified microstructure
is composed of θ(Al2Cu), α(Al) and ξ(Ag2Al) phases. The liquidus temperature and solidus temperature are determined as 778 and 827 K, respectively. The alloy melt
undercooled amounts up to ΔT
Max=171 K (0.20T
L). Its microstructural evolution is investigated based on the theoretical analysis of undercooling behavior and nucleation
mechanics. It is found that the undercooling increases with the decrease of the diameter of the alloy droplet. When ΔT<78 K, the primary θ(Al2Cu) phase of the alloy grows into coarse dendrite. When 78 K⩽ΔT⩽171 K, its refined θ(Al2Cu) phase grows alternatively with α(Al) phase. Once ΔT⩾171 K, its microstructure is characterized by the anomalous (θ+α+ξ) ternary eutectic.
Supported by the National Natural Science Foundation of China (Grant Nos. 50121101 and 50395105) 相似文献
10.
The rearrangement of the Fermi surface in a diluted two-dimensional electron gas beyond the topological quantum critical point has been examined within an approach based on the Landau theory of Fermi liquid and a nonperturbative functional method. The possibility of a transition of the first order in the coupling constant at zero temperature between the states with a three-sheet Fermi surface and a transition of the first order in temperature between these states at a fixed coupling constant has been shown. It has also been shown that a topological crossover, which is associated with the joining of two sheets of the Fermi surface and is characterized by the maxima of the density of states N(T) and ratio C(T)/T of the specific heat to the temperature, occurs at a very low temperature T ⋄ determined by the structure of a state with the three-sheet Fermi surface. A momentum region where the distribution n(p, T) depends slightly on the temperature, which is manifested in the maximum of the specific heat C(T) near T *, appears through a crossover at temperatures T ∼ T * > T ⋄. It has been shown that the flattening of the single-particle spectrum of the strongly correlated two-dimensional electron gas results in the crossover from the Fermi liquid behavior to a non-Fermi liquid one with the density of states N(T) ∝ T −α with the exponent α }~ 2/3. 相似文献
11.
L. N. Strunov V. G. Antonenko S. B. Borzakov Yu. T. Borzunov E. V. Chernykh V. F. Chumakov Yu. I. Ivanshin S. A. Dolgii M. Finger Jr. M. Finger L. B. Golovanov D. K. Guriev A. Janata A. D. Kovalenko V. A. Krasnov N. A. Kuzmin A. N. Livanov P. K. Maniakov E. A. Matyushevsky A. A. Morozov G. P. Nikolaevsky A. A. Nomofilov Tz. Panteleev I. L. Pisarev Yu. P. Polunin A. N. Prokofiev V. Yu. Prytkov P. A. Rukoyatkin V. I. Sharov R. A. Shindin M. Slunečka V. Slunečková A. Yu. Starikov T. A. Vasiliev I. P. Yudin I. V. Zaitsev A. A. Zhdanov V. N. Zhmyrov 《The European physical journal. Special topics》2008,162(1):125-132
The measurements of np-spin observables at 0° have been performed for the first time on the Delta-Sigma experimental facility of LHE JINR up to
P
n
= 4.5 GeV/c using the monochromatic neutron beam. They include detailed measurements of the Δσ
L(np) spin differences and the study of the np → pn elastic charge-exchange process. In the Δσ
L(np) and −Δσ
L(I = 0) energy dependencies over the energy region Tkin = 1.2–3.7 GeV the peculiarity at 1.8 GeV was observed. Such energy behavior was predicted by the QCD approach as a signal
of the NN → 6q phase transition. For the exhaustive investigation of this effect it is necessary to measure the energy dependence of the
complete set of np observables with both longitudinal (L) and transverse (T) polarizations of the neutron beam and proton target. This will allow Direct Reconstruction of all three NN forward Scattering Amplitudes (DRSA) to be performed, and the observed peculiarity to be checked around Tkin = 1.8 GeV and at the higher energies using the Argand diagrams method. 相似文献
12.
We have investigated the absorption spectrum of thin films of the superionic conductor RbCu4Cl3I2 synthesized on NaCl crystalline substrates. It is shown that the electron and exciton excitations in the energy interval
3–6 eV are associated with optical transitions in the CuHal sublattice, and the edge of the fundamental band is controlled
by optical transitions in the Cu(II)Hal sublattice. It is found that the large band gap of this compound (E
g
=3.86 eV) in comparison with those of CuCl and CuI is a result of the small number of Cu ions in the second coordination sphere.
The temperature dependence of the spectral position and half-width of the low-temperature exciton band reveals features associated
with the phase transitions γ→β (T
c1=170 K) and β→α (T
c2=220 K) and with disordering of the cation sublattice attendant to the transition to the superionic state.
Fiz. Tverd. Tela (St. Petersburg) 40, 1022–1026 (June 1998) 相似文献
13.
14.
D. M. Zashchirinskii L. I. Koroleva A. S. Morozov Yu. V. Dolzhenkova 《Physics of the Solid State》2011,53(2):316-319
The magnetocaloric effect ΔT has been studied by a direct method in two samples of the manganite Sm0.55Sr0.45MnO3, namely, a single crystal (sample A) and a ceramic sample (sample C). The temperature dependences of the ΔT effect of both samples exhibit a maximum at T
max = 143.3 K for the sample A and T
max = 143 K for the sample C. In these maxima, the values of the ΔT effect are 0.8 and 0.4 K in the magnetic field H = 14.2 kOe for the samples A and C, respectively. In addition, the ΔT(T) curve of the sample A has a minimum at T
min = 120 K, in which ΔT = −0.1 K. The maximum value of the ΔT effect increases with an increase in the magnetic field H in the range of magnetic fields up to 14.2 kOe, and the rate of this increase at H > 8 kOe is higher than that at H < 8 kOe. These features of the ΔT effect are explained by the presence of ferromagnetic and antiferromagnetic A- and CE-type clusters in the samples. 相似文献
15.
The effect of mechanical contacts between γ-Fe2O3 particles on the temperature of the γ-α structural transition in them is established by magnetic studies and differential
thermal analysis (DTA). The sample in which γ-Fe2O3 particles had no mechanical contacts with one another remained in the ferromagnetic state up to T
C = 630°C and had two exothermal DTA peaks. The first peak almost coincided with the Curie temperature, while the second peak
attributed to the γ → α structural transition corresponded to 760°C. The magnetic transition for particles with a larger number
of contacts was shadowed by the γ → α structural transition with a temperature lowered to 550°C. 相似文献
16.
Gotter M Sottmann T Baciu M Olsson U Wennerström H Strey R 《The European physical journal. E, Soft matter》2007,24(3):277-295
Time-resolved small-angle neutron scattering (TR-SANS) was employed to observe temperature-induced phase transitions from
the sponge (L
3 to the lamellar ( L
α phase, and vice versa, in the water-oil (n -decane)-non-ionic surfactant ( C12E5 system using both bulk and film contrast. Samples of different bilayer volume fractions φ and solvent viscosities η were
investigated applying various amplitudes of temperature jump ΔT . The findings of a previous 2H -NMR study could be confirmed, where the lamellar phase formation was determined to occur through a nucleation and growth
process, while it was concluded that the L
3 -phase develops in a mechanistically different and more rapid manner involving uncorrelated passage formation. Likewise,
the kinetic trends of the nucleation and growth transition (decreased transition time with increase of φ and ΔT were witnessed once again. Additionally, NMR and SANS data that demonstrate a strong dependency of that process on solvent
viscosity η are presented. Contrariwise, it is made evident via both SANS and NMR results that the L
α -to-L
3 transition time is independent (within experimental sensitivity) of the varied parameters (φ , ΔT , η . Unusual scattering evolution in one experiment, originating from a highly ordered lamellar phase, intriguingly hints
that a major rate determining factor is the disruption of long-range order. Furthermore, the bulk contrast investigations
give insight into structure peak shifts/development during the transitions, while the film contrast experiments prove the
bilayer thickness to be constant throughout the phase transitions and show that there is no evidence for a change in the short-range
order of the bilayer structure. The latter was considered possible, due to the different topology of the L
3 and L
α phases. Lastly, an unexpected yet consistent appearance of anisotropic scattering is detected in the L
3 -to- L
α transitions. 相似文献
17.
I. N. Izosimov V. G. Kalinnikov A. A. Solnyshkin 《Physics of Particles and Nuclei》2011,42(6):963-997
The β transition strength function S
β(E) is the nuclear excitation energy distribution of moduli squared of the β-decay-type matrix elements. The function S
β(E) determines the characteristics of β decay, the spectra of accompanying radiation, and the probabilities of delayed processes
following the β decay. Until recently, tools widely used for experimental investigation of the S
β(E) structure have been total absorption gamma spectrometers and total absorption gamma-ray spectroscopy (TAGS) which could
not provide high energy resolution. Development of experimental techniques allows nuclear spectroscopy methods with high energy
resolution to be used for studying the fine structure of S
β(E). A thorough investigation of this kind has been carried out for a number of nuclei produced at the YASNAPP-2 facility in
Dubna. In this review, studies involving works on measuring the fine structure of S
β(E) in spherical and deformed nuclei are analyzed. Modern nuclear spectroscopy methods made it possible to identify the splitting
of peaks from nuclear deformation in S
β(E) for Gamow-Teller (GT) transitions. The resonance nature of S
β(E) for first-forbidden (FF) transitions in both spherical and deformed nuclei is experimentally proven. It is shown that for
some nuclear excitation energies, FF transitions can be comparable in intensity with GT transitions. Criteria for verifying
the completeness of nuclear decay schemes are considered. The S
β(E) functions obtained by TAGS and by the high-resolution spectroscopy are compared. 相似文献
18.
Osamu Yamashita Hirotaka Odahara Takahiro Ochi Kouji Satou 《Applied Physics A: Materials Science & Processing》2009,94(1):57-64
The resultant local Seebeck coefficient α
R (=α
S−α
T) at the interface of a thermoelement has not yet been measured, although it is an important factor governing the thermoelectric
efficiency, where α
S is the local Seebeck coefficient and α
T is the one caused by the Thomson effect. It is shown in this paper that α
S, α
T, and α
R of the p- and n-type Cu/Bi–Te/Cu composites are obtained analytically and experimentally on the assumption that the local temperature of
the composite on which the temperature difference ΔT is imposed varies linearly with changes in position along the composite. They were indeed estimated as a function of position
from the local experimental data of R,ΔI,ΔT, and V generated by applying an additional current of ±I to the composite, where R is the electrical resistance and ΔI is a current generated by the composite. As a result, it was found that the absolute values of α
S at the hot interface of the p- and n-type composites are approximately 1.5 and 1.4 times higher than their lowest values in the middle region of the composite,
respectively, while those of α
T are less than 8% of α
S all over the composite and are so small that the relation α
R≈α
S can be held. We thus succeeded in measuring α
R at the interfaces of the composite. 相似文献
19.
M. Modarres M. M. Yazdanpanah F. Zolfagharpour 《The European Physical Journal A - Hadrons and Nuclei》2007,32(3):327-333
The electromagnetic polarizabilities of the nucleon are shown to be essentially composed of the nonresonant α
p(E
0+) = + 3.2, α
n(E
0+) = + 4.1, the t-channel α
t
p, n = - β
t
p, n = + 7.6 and the resonant β
p, n(P
33(1232)) = + 8.3 contributions (in units of 10-4fm^3). The remaining deviations from the experimental data Δα
p = 1.2±0.6, Δβ
p = 1.2±0.6, Δα
n = 0.8±1.7 and Δβ
n = 2.0±1.8 are contributed by a larger number of resonant and nonresonant processes with cancellations between the contributions.
This result confirms that dominant contributions to the electric and magnetic polarizabilities may be represented in terms
of two-photon coupling to the σ-meson having the predicted mass m
σ
= 666MeV and two-photon width Γ
γγ
= 2.6keV. 相似文献
20.
The effect of γ irradiation on the temperature hysteresis in dielectric permittivity ɛ and loss tangent tan δ of crystalline Rb2ZnBr4 has been studied in the vicinity of the incommensurate-commensurate phase transition. The ɛ(T) and tan δ(T) curves were found to exhibit anomalies in the form of maxima. Hysteresis was observed in the measured properties, including
the transition temperature T
c
(ΔT=T
c
h
−T
c
c
), in both unirradiated and irradiated samples. It is shown that, as the radiation dose increases the extent of the hysteresis
ΔT increases, the values of ɛ
max and tan δ
max at the transition point decrease, and the anomalies wash out.
Fiz. Tverd. Tela (St. Petersburg) 40, 1911–1914 (October 1998) 相似文献