共查询到20条相似文献,搜索用时 31 毫秒
1.
A. U. Sheleg T. I. Dekola N. P. Tekhanovich A. M. Luginets 《Physics of the Solid State》1999,41(3):445-446
The specific heat of the KTiOPO4 crystal has been measured with a vacuum adiabatic calorimeter within the 80–300 K range. A peak-shaped anomaly in the specific
heat indicating a phase transition has been revealed in the C
p (T) curve at T≅279 K. Numerical integration of smoothened experimental C
p (T) curves yielded the thermodynamic functions of KTiOPO4, namely, the entropy, enthalpy, and reduced Gibbs energy. The entropy and enthalpy of the observed transition have been determined.
Fiz. Tverd. Tela (St. Petersburg) 41, 497–498 (March 1999) 相似文献
2.
B. A. Strukov E. P. Ragula S. Yu. Stefanovich I. V. Shnaidshtein S. V. Arkhangel’skaya A. Onodera 《Physics of the Solid State》1998,40(7):1193-1195
The specific heat of the ceramic and the permittivity of a single-crystal sample of LaBSiO5, a new ferroelectric in the stilwellite family, were measured in a temperature range which includes the phase transition
point (T
C=140 °C). The excess entropy of the phase transition ΔS=1.05 J/mol · K and the Curie-Weiss constant C
C-W=3.2×103 K were determined. The results indicate that the phase transition in this crystal is of a “mixed” nature and exhibits features
of a displacement-type transition and an order-disorder transition.
Fiz. Tverd. Tela (St. Petersburg) 40, 1310–1312 (July 1998) 相似文献
3.
Heat capacity of Rb2ZnBr4 as a function of γ irradiation dose has been measured within the 85–300 K range by the adiabatic calorimeter technique. It is shown that, as
the irradiation dose increases, the heat capacity peak in the vicinity of the incommensurate-commensurate first-order phase
transition (PT) decreases, and the transition temperature T
c
increases. The heat capacity peak in the region of the second-order PT at T
3=112 K does not depend on γ irradiation, both in magnitude and in position, just as the heat capacity throughout the remainder of the temperature range
studied.
Fiz. Tverd. Tela (St. Petersburg) 40, 1106–1108 (June 1998) 相似文献
4.
V. M. Egorov Yu. M. Baikov N. F. Kartenko B. T. Melekh Yu. N. Filin 《Physics of the Solid State》1998,40(11):1911-1914
Differential scanning calorimetry was used to study phase transitions (PT) in the perovskite BaCeO3. It is shown that its phase state is determined by a second-order λ transition at T
tr=520–540 K and a first-order δ transition at T
tr=600–670 K. Differences in PT parameters between ceramic and fused BaCeO3 have been established.
Fiz. Tverd. Tela (St. Petersburg) 40, 2109–2112 (November 1998) 相似文献
5.
The specific heat of the cryolites (NH4)3Ga1−x
ScxF6 with x=1.0, 0.1, and 0 was measured. The thermodynamic parameters of the phase transitions were determined. A previously unknown
phase transition was found in the scandium compound at T=243 K.
Fiz. Tverd. Tela (St. Petersburg) 41, 523–528 (March 1998) 相似文献
6.
N. E. Sluchanko A. N. Azarevich A. V. Bogach S. Yu. Gavrilkin V. V. Glushkov S. V. Demishev A. V. Dukhnenko A. B. Lyashchenko K. V. Mitsen V. B. Filipov 《JETP Letters》2011,94(8):642-646
The specific heat of the ZrB12 compound in the normal and superconducting states (T
C
≈ 6 K) has been studied in the 1.9–7 K temperature range for high-quality single crystals with different relative contents
of boron isotopes. For Zr10B12, ZrnatB12, and Zr11B12 dodecaborides, the electron density of states and the electronphonon coupling constant, λe-ph ∼ 0.4, are found. The dependence of the thermodynamic and upper critical fields, as well as of the Ginzburg-Landau parameter
(κ = 0.8–1.14) on temperature and isotope composition is determined. The results suggest the existence of the magnetic field
induced phase transition at T* = 4–5 K, which is not related to the transition from type-I to type-II superconductivity. The possibilities of the existence
of two-gap superconductivity and a structural phase transition at T* in zirconium dodecaboride are discussed. 相似文献
7.
The experimental results on the change in the crystal structure and specific heat of nonstoichiometric titanium carbide TiCy (0.5<y<0.65) near disorder-order phase transitions are reported. It is established that at temperatures below 1000 K the ordered
phases Ti2C with cubic and trigonal symmetry and an orthorhombic ordered phase Ti3C2 form in titanium carbide by a close-to-first-order phase transition mechanism. The temperatures and heats of order-disorder
phase transformations are determined.
Pis’ma Zh. éksp. Teor. Fiz. 69, No. 9, 631–637 (10 May 1999) 相似文献
8.
A. G. Gamzatov A. M. Aliev K. Sh. Khizriev I. K. Kamilov A. S. Mankevich I. E. Korsakov 《Physics of the Solid State》2011,53(11):2271-2274
The heat capacity of the manganite La0.87K0.13MnO3 has been measured in the temperature range 80–350 K. The nature of the ferromagnetic phase transition and the critical properties
of heat capacity near the Curie temperature have been studied. The regularities of variations in the universal critical parameters
near the phase transition point have been established. The calculated critical exponent and amplitudes of the heat capacity
with allowance for corrections on the scaling (α = −0.13 and A
+/A
− = 1.178) correspond to the critical behavior of the 3D Heizenberg model. 相似文献
9.
I. A. Smirnov L. S. Parfen’eva A. Jezowski H. Misiorek S. Krempel-Hesse F. Ritter W. Assmus 《Physics of the Solid State》1999,41(9):1418-1421
The electrical and thermal conductivities of an YbInCu4 polycrystalline sample have been measured within the 4.2–300-K range. The behavior of the heat conductivity has been found
to change sharply above and below T
v
=70–75 K, the temperature corresponding to an isostructural phase transition from a state with an integral valence (T>T
v
) to a mixed-valence state (T<T
v
) of Yb ions. A preliminary qualitative analysis of the results is presented.
Fiz. Tverd. Tela (St. Petersburg) 41, 1548–1551 (September 1999) 相似文献
10.
I. O. Bashkin M. V. Nefedova V. G. Tissen E. G. Ponyatovskii 《Physics of the Solid State》1998,40(12):1950-1952
The pressure dependence of the superconducting transition temperature in TiD0.74 has been measured up to 30 GPa in a diamond high-pressure chamber. It is found that the deuteride TiD0.74 becomes a superconductor at pressures corresponding to the transition to the high-pressure ζ phase, with a transition temperature that increases from 4.17 to 4.43 K in the interval P=14–30 GPa. The value extrapolated to atmospheric pressure T
c
(0)=4.0 K is significantly lower than the superconducting transition temperature (T
c
=5.0 K) measured earlier in the metastable state obtained by quenching TiD0.74 under pressure. It is assumed that the significant difference of the extrapolated value from the superconducting transition
temperature in the metastable state after quenching under pressure is caused by a phase transition on the path from the stability
region of the ζ phase under pressure to the region of the metastable state at atmospheric pressure.
Fiz. Tverd. Tela (St. Petersburg) 40, 2153–2155 (December 1998) 相似文献
11.
A. Kovalev H. Mueller M. V. Kartsovnik 《Journal of Experimental and Theoretical Physics》1998,86(3):578-581
Specific heat measurements of a single crystal of the organic metal (BEDT-TTF)2KHg(SCN)4 have been carried out at low temperatures and under a magnetic field of up to 14 T. A jump in the specific heat of about
0.1 J/mol·K, which corresponds to the antiferromagnetic phase transition, has been observed. The magnetic field is found to
decrease the transition temperature at any field orientation. The strongest effect was found to take place in the field direction
along the highly conducting ac plane.
Zh. éksp. Teor. Fiz. 113, 1058–1063 (March 1998)
Published in English in the original Russian journal. Reproduced here with stylistic changes by the Translation Editor. 相似文献
12.
AbstractA study has been made of the order-disorder phase transformations in the homogeneity region of the VCy nonstoichiometric cubic vanadium carbide (0.66<y<0.88). It has been established that an ordered V6C5 phase with monoclinic (space group C2/m) or trigonal (P31) symmetry, and a cubic (space group P4332) ordered V8C7 phase can form in the VCy carbide below 1450 K, depending on the actual composition. The effect of off-stoichiometry and structural vacancy ordering
on the specific heat of the VCy carbide has been investigated. The temperatures and heats of the reversible order-disorder equilibrium transitions have been
determined. The ordering in the VCy carbide is shown to be a first-order phase transition. An equilibrium diagram of the V-C system taking into account ordering
in the nonstoichiometric vanadium carbide has been constructed.
Fiz. Tverd. Tela (St. Petersburg) 41, 529–536 (March 1999) 相似文献
13.
A. V. Prokof’ev I. A. Smirnov W. Assmus F. Büllesfeld A. Jezowski 《Physics of the Solid State》1998,40(11):1896-1897
Thermal conductivity ϰ of single-crystal (VO)2P2O7 has been studied within the 4–300 K range. A break was found in the ϰ(T) relation about 200 K, in the region of the transition from diffuse antiferromagnetic ordering (200–4 K) to a classical paramagnet
(T=200–300 K). In the low-temperature domain (4–200 K), one may expect an additional contribution to ϰ(T) from the magnon component of thermal conductivity.
Fiz. Tverd. Tela (St. Petersburg) 40, 2093–2094 (November 1998) 相似文献
14.
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
15.
I. V. Zolotukhin S. V. Spitsina L. I. Yanchenko L. N. Korotkov 《Physics of the Solid State》1999,41(11):1891-1893
Macroscopic fractal aggregates of KH2PH4 (KDP) measuring up to 500 μm have been obtained. The fractal structure forms as a result of the precipitation of KDP particles
from a supersaturated aqueous solution in the presence of a temperature gradient followed by a diffusioncontrolled mechanism
of aggregation. The electron-microscopic analysis performed has shown that the fractals are formed predominantly from crystallites
of the tetragonal modification measuring ∼1 μm. The dielectric constant (ɛ) of fractal KH2PO4 has been measured in the temperature range 80–300 K. A characteristic anomaly has been discovered on the ɛ(T) curve in the vicinity of 122 K, which attests to a ferroelectric phase transition. The absolute value of ɛ is significantly smaller than the components ɛ
11 and ɛ
33 for KH2PO4.
Fiz. Tverd. Tela (St. Petersburg) 41, 2059–2061 (November 1999) 相似文献
16.
Anomalies of the low-temperature specific heat of the cuprates La2CuO4 and La2−x
MxCuO4 (M = Sr, Ba)
K. A. Kvavadze M. M. Nadareishvili G. G. Basiliya D. D. Igitkhanishvili L. A. Tarkhnishvili Sh. V. Dvali 《Physics of the Solid State》1997,39(6):897-900
The low-temperature specific heat of the cuprates La2CuO4, La2−x
MxCuO4 (M = Sr, Ba) in the temperature interval 2–45 K has been investigated by the technique of pulsed differential calorimetry.
It is found that the coefficient of the residual linear term in the specific heat remains constant in the entire experimental
temperature interval. It is shown that La atoms play a special role in the formation of the anomaly, associated with the specific
nature of the interaction of these atoms with their environment, in the acoustic region of the phonon spectrum of these objects
near 6 meV.
Fiz. Tverd. Tela (St. Petersburg) 39, 1000–1004 (June 1997) 相似文献
17.
V. S. Gaviko V. E. Arkhipov A. V. Korolev V. E. Naish Ya. M. Mukovskii 《Physics of the Solid State》1999,41(6):969-973
A study is made of phase transitions in doped La0.9Sr0.1MnO3 compounds using combined x-ray, electrical, and magnetic measurements. Structural phase transitions are observed accompanied
by a change in the cell volume at temperatures of 100–110 K and 300–340 K. These structural changes are found to be related
to different contributions of the rhombic Jahn-Teller Q
2 mode to the formation of the crystal lattice. The structural transition at 100–110 K is accompanied by distinctive magnetic
and electrical properties. The data are analyzed in detail.
Fiz. Tverd. Tela (St. Petersburg) 41, 1064–1069 (June 1999) 相似文献
18.
A study of the thermal expansion coefficient (TEC) of the ScxTi1−x
Fe2 itinerant magnets has been made within the 5–1200 K range at the transition from the TiFe2 antiferromagnet (T
N=270 K) to the ScFe2 ferromagnet (T
C=540 K). A negative TEC magnetic contribution α
m(T) has been found, which is associated with the formation of spin-fluctuation-induced local magnetic moments in both the magnetically
ordered and the paramagnetic state. The specific features in the α
m(T) dependence are shown to be due to the shape of the density-of-states function near the Fermi level.
Fiz. Tverd. Tela (St. Petersburg) 41, 2174–2178 (December 1999) 相似文献
19.
The specific heat C
total of crystalline and amorphous Eu2(MoO4)3 is measured in the temperature interval 4.5–30 K. The amorphous state is obtained by applying pressure ∼7 GPa at room temperature.
It is found that the specific heat of the crystal at T⩽7.5 K is described by a cubic function of temperature, while the specific
heat of the amorphous sample has a strongly non-Debye character in the entire experimental temperature interval. The curve
of C
total for amorphous europium molybdate is analyzed in a model of soft atomic potentials, and it is shown that it agrees well with
universal low-temperature anomalies of the specific heat of classical glasses obtained by quenching from the liquid.
Pis’ma Zh. éksp. Teor. Fiz. 68, No. 8, 623–627 (25 October 1998) 相似文献
20.
I. K. Kamilov A. G. Gamzatov A. B. Batdalov A. S. Mankevich I. E. Korsakov 《Physics of the Solid State》2010,52(4):789-793
The magnetocaloric effect and the heat capacity of La1 − x
K
x
MnO3 (x = 0.1, 0.15, 0.175) ceramic samples have been studied at temperatures in the range 77–350 K and in magnetic fields of up
to 27 kOe. The technique for preparing the samples has been described. The heat capacity anomalies related to the ferromagnetic-paramagnetic
magnetic phase transition have been revealed and interpreted. It has been demonstrated that the change in the magnetic entropy
ΔS calculated from the data on the heat capacity C
p
and direct measurements of the magnetocaloric effect ΔT reaches values that are of practical interest. 相似文献