共查询到20条相似文献,搜索用时 31 毫秒
1.
L. T. Denisova L. A. Irtyugo Yu. F. Kargin V. V. Beletskii V. M. Denisov 《Inorganic Materials》2016,52(6):584-586
Gd2Sn2O7 gadolinium stannate with the pyrochlore structure has been prepared by solid-state reaction and its high-temperature heat capacity has been determined by differential scanning calorimetry in the temperature range 350–1020 K. The Cp(T) data are shown to be well represented by the classic Maier–Kelley equation. The experimental Cp(T) data have been used to evaluate the thermodynamic functions of gadolinium stannate: enthalpy increment H°(T)–H°(339 K), entropy change S°(T)–S°(339 K), and reduced Gibbs energy Ф°(Т). 相似文献
2.
L. T. Denisova L. A. Irtyugo Yu. F. Kargin V. V. Beletskii V. M. Denisov 《Inorganic Materials》2017,53(1):93-95
Tb2Sn2O7 has been prepared by solid-state reaction in air at 1473 K over a period of 200 h and its isobaric heat capacity has been studied experimentally in the range 350–1073 K. The C p(T) data for this compound have no extrema and are well represented by the classic Maier–Kelley equation. The experimental C p(T) data have been used to evaluate the thermodynamic properties of terbium stannate (pyrochlore structure): enthalpy increment H°(T)–H°(350 K), entropy change S°(T)–S°(350 K), and reduced Gibbs energy Ф°(Т). 相似文献
3.
L. T. Denisova L. A. Irtyugo Yu. F. Kargin N. V. Belousova V. V. Beletskii V. M. Denisov 《Inorganic Materials》2018,54(4):361-365
The Dy2Ge2O7 and Ho2Ge2O7 pyrogermanates have been prepared by solid-state reactions in several sequential firing steps in the temperature range 1237–1473 K using stoichiometric mixtures of Dy2O3 (or Ho2O3) and GeO2. The heat capacity of the synthesized germanates has been determined as a function of temperature by differential scanning calorimetry in the range 350–1000 K. The experimentally determined C p (T) curves of the dysprosium and holmium germanates have no anomalies and are well represented by the Maier–Kelley equation. The experimental C p (T) data have been used to evaluate the thermodynamic functions of the Dy2Ge2O7 and Ho2Ge2O7 pyrogermanates: enthalpy increment H°(T)–H°(350 K), entropy change S°(T)–S°(350 K), and reduced Gibbs energy Ф°(T). 相似文献
4.
L. T. Denisova L. A. Irtyugo Yu. F. Kargin V. M. Denisov V. V. Beletskii A. A. Shubin 《Inorganic Materials》2016,52(8):811-814
The Eu2Sn2O7 compound has been prepared by solid-state reaction (by sequentially firing a stoichiometric mixture of Eu2O3 and SnO2 in air at 1273 and 1473 K) and its heat capacity has been determined by differential scanning calorimetry in the temperature range 370–1000 K. The heat capacity data have been used to evaluate the thermodynamic properties of europium stannate: enthalpy increment H°(T)–H°(370 K), entropy change S°(T)–S°(370 K), and reduced Gibbs energy Ф°(T). Raman spectra of Eu2Sn2O7 polycrystals with the pyrochlore structure have been measured in the range 200–1200 cm–1. 相似文献
5.
A. V. Gusarov 《High Temperature》2016,54(5):771-774
The–(G°(T)–H°(0))/T Gibbs energy functions have been calculated for Sc2 at Т = 2000 K in the context of recent data on the low-lying electron states for this kind of molecules. In particular, some recent experimental results on the vapor composition over scandium are presented in this study. The data on the measured scandium vapor composition have been processed using the evaluated Gibbs energy function values. The advised dissociation energy value for Sc2 is found to be D°0(Sc2) = 7750 ± 1750 cm–1. 相似文献
6.
The heat capacity of InVO4 has been determined by differential scanning calorimetry in the temperature range 339–1089 K. The experimental Cp(T) data have been used to evaluate the thermodynamic functions of indium orthovanadate: enthalpy increment H°(T)–H°(339 K), entropy change S°(T)–S°(339 K), and reduced Gibbs energy Ф°(Т). The specific heats of GaVO4 and TlVO4 have been evaluated. 相似文献
7.
B. K. Kasenov E. S. Mustafin Sh. B. Kasenova Zh. I. Sagintaeva S. T. Edil’baeva S. Zh. Davrenbekov 《High Temperature》2009,47(1):27-32
The ceramic technology is employed for synthesizing manganites of composition Nd Mg 3 I Mg3Mn4O12(MeI-Li, Na, K). The X-ray technique is used to find that the compounds crystallize in tetragonal syngony. The parameters of their crystal lattices are determined. Their heat capacities are experimentally determined in the range from 298.15 to 673 K, which enables one to reveal second-order phase transitions. In view of these transitions, equations describing the C p ° ~ f(T) dependence are derived, and the thermodynamic functions C p ° (T), H°(T)-H°(298.15), S°(T), and Φ xx (T) are calculated. 相似文献
8.
A. N. Georgobiani B. G. Tagiev O. B. Tagiev S. A. Abushov F. A. Kazymova T. Sh. Gashimova Xu Xurong 《Inorganic Materials》2009,45(2):116-122
The photoluminescence (PL) spectra and Eu2+ excited state lifetime of EuGa2S4 and EuGa2S4:Er3+ have been studied in the range 78–500 K. The spectra show a band at 545 nm, due to the 4f 65d → 4f 7(8 S 7/2) transition. With increasing temperature, the full width at half maximum Γ(T) of the PL band of EuGa2S4 and EuGa2S4:Er3+ crystals increases from 0.15 to 0.22 and from 0.13 to 0.19 eV, respectively. Over the entire temperature range studied, Γ(T) is a linear function of T 1/2. The 545-nm emission intensity and Eu2+ excited state lifetime in EuGa2S4 and EuGa2S4:Er3+ vary exponentially with temperature. The luminescence quenching energies evaluated from the Arrhenius plots of I(103/T) and τ(103/T) coincide (0.10 eV) within the error of determination. 相似文献
9.
Mohamed Baazaoui Sobhi Hcini Michel Boudard Sadok Zemni Mohamed Oumezzine 《Journal of Superconductivity and Novel Magnetism》2015,28(7):1887-1893
The critical behavior of perovskite manganite La0.67Ba0.33Mn0.95Fe0.05O3 at the ferromagnetic–paramagnetic has been analyzed. The results show that the sample exhibited the second-order magnetic phase transition. The estimated critical exponents derived from the magnetic data using various such as modified d’Arrott plot Kouvel–Fisher method and critical magnetization M(T C, H). The critical exponents values for the La0.67Ba0.33Mn0.95Fe0.05O3 are close to those expected from the mean field model β = 0.504 ± 0.01 with T C = 275661 ± 0.447 (from the temperature dependence of the spontaneous magnetization below T C ), γ = 1.013 ± 0.017 with T C = 276132 ± 0.452 (from the temperature dependence of the inverse initial susceptibility above T C ), and δ = 3.0403 ± 0.0003. Moreover, the critical exponents also obey the single scaling equation of M(H, ε) = |ε| β f ±(H/|ε| β+γ ). 相似文献
10.
B. B. Tumataeva Sh. B. Kasenova B. K. Kasenov E. S. Mustafin Zh. I. Sagintaeva S. Zh. Davrenbekov 《High Temperature》2007,45(5):645-648
The calorimetric method is used to investigate the heat capacity of DyMeIICr2O5.5(MeII-Mg, Ca) chromites in the range from 298.15 to 673 K. The C p 0 ~ f(T) curves exhibit λ-like effects at 348 and 548 K for DyMgCr2O5.5 and at 473 K for DyCaCr2O5.5, which apparently relate to second-order phase transitions. The temperature dependences are calculated for thermodynamic functions C p 0 (T), H 0(T)-H 0(298.15), S 0(T), and Φ**(T). 相似文献
11.
V. S. Sulyaeva V. A. Shestakov Yu. M. Rumyantsev M. L. Kosinova 《Inorganic Materials》2018,54(2):133-139
Using mechanochemical synthesis, we have prepared zirconium borohydride, Zr(BH4)4, as a precursor for ZrB2 film growth by chemical vapor deposition. We have carried out the thermodynamic modeling of phase formation processes in the Zr–B–(N)–H and Zr–B–(N)–H–O systems in a wide temperature range, from 100 to 2500°C, at various p(H2)/p(Zr(BH4)4) and p(NH3)/p(Zr(BH4)4) partial pressure ratios in the starting gas mixtures. A process has been proposed for the growth of zirconium diboride films by Zr(BH4)4 decomposition using two techniques: chemical vapor deposition and plasma-enhanced chemical vapor deposition. We also developed a process for the growth of multilayer ZrB2-and BC x N y -based structures. 相似文献
12.
We report the results of magnetic, magnetocaloric properties, and critical behavior investigation of the double-layered perovskite manganite La1.4(Sr0.95Ca0.05)1.6Mn2O7. The compounds exhibits a paramagnetic (PM) to ferromagnetic (FM) transition at the Curie temperature T C = 248 K, a Neel transition at T N = 180 K, and a spin glass behavior below 150 K. To probe the magnetic interactions responsible for the magnetic transitions, we performed a critical exponent analysis in the vicinity of the FM–PM transition range. Magnetic entropy change (??S M) was estimated from isothermal magnetization data. The critical exponents β and γ, determined by analyzing the Arrott plots, are found to be T C = 248 K, β = 0.594, γ = 1.048, and δ = 2.764. These values for the critical exponents are close to the mean-field values. In order to estimate the spontaneous magnetization M S(T) at a given temperature, we use a process based on the analysis, in the mean-field theory, of the magnetic entropy change (??S M) versus the magnetization data. An excellent agreement is found between the spontaneous magnetization determined from the entropy change [(??S M) vs. M 2] and the classical extrapolation from the Arrott curves (µ0H/M vs. M 2), thus confirming that the magnetic entropy is a valid approach to estimate the spontaneous magnetization in this system and in other compounds as well. 相似文献
13.
A. V. Tyurin K. S. Gavrichev L. N. Golushina V. E. Gorbunov V. P. Zlomanov 《Inorganic Materials》2005,41(11):1139-1143
The heat capacity of Ga2Se3 is measured from 14 to 320 K by adiabatic calorimetry. The smoothed heat capacity data are used to evaluate temperature-dependent thermodynamic functions (entropy, enthalpy increment, and reduced Gibbs energy) of gallium selenide. Under standard conditions, the thermodynamic properties of Ga2Se3 are C p 0 (298.15 K) = 120.8 ± 0.2 J/(K mol), S0(298.15 K) = 180.4 ± 0.4 J/(K mol), H0(298.15 K) - H0(0) = 25.32 ± 0.05 kJ/mol, and Φ0(298.15 K) = 95.52 ± 0.19 J/(K mol). The Debye characteristic temperature of Ga2Se3 evaluated from heat capacity data is 340 ± 10 K. 相似文献
14.
L. B. Vedmid' V. F. Balakirev A. M. Yankin Yu. V. Golikov 《Inorganic Materials》2005,41(12):1357-1359
The phase equilibria involved in the thermal dissociation of RMnO3 (R = Dy, Yb, Lu) were studied in the range 973–1173 K by a static method in a vacuum circulation unit and by x-ray diffraction analysis of quenched solid phases. The RMnO3 manganites were shown to dissociate by the reaction RMnO3 = 1/2R2O3 + MnO + 1/4O2. The temperature dependences of the equilibrium oxygen pressure and Gibbs energy change in this reaction were determined for the three compounds. The experimental data were used to evaluate the standard thermodynamic functions of formation of RMnO3 from R2O3 and Mn2O3: ΔH0(T) = ?88.93 kJ/mol, Δ S0(T) = 46.56 J/(mol K) for DyMnO3; ΔH0(T) = ?130.95 kJ/mol, Δ S0(T) = 86.25 J/(mol K) for YbMnO3; ΔH0(T) = ?142.94 kJ/mol, Δ S0(T) = 102.87 J/(mol K) for LuMnO3. 相似文献
15.
Devina Sharma Jagdish Kumar Arpita Vajpayee Ranjan Kumar P. K. Ahluwalia V. P. S. Awana 《Journal of Superconductivity and Novel Magnetism》2011,24(6):1925-1931
In the present study, we report an intercomparison of various physical and electronic properties of MgB2 and AlB2. In particular, the results of phase formation, resistivity ρ(T), thermoelectric power S(T), magnetization M(T), heat capacity (C P ), and electronic band structure are reported. The original stretched hexagonal lattice with a=3.083 Å, and c=3.524 Å of MgB2 shrinks in c-direction for AlB2 with a=3.006 Å, and c=3.254 Å. The resistivity ρ(T), thermoelectric power S(T) and magnetization M(T) measurements exhibited superconductivity at 39 K for MgB2. Superconductivity is not observed for AlB2. Interestingly, the sign of S(T) is +ve for MgB2 the same is ?ve for AlB2. This is consistent with our band structure plots. We fitted the experimental specific heat of MgB2 to Debye–Einstein model and estimated the value of Debye temperature (Θ D) and Sommerfeld constant (γ) for electronic specific heat. Further, from γ, the electronic density of states (DOS) at Fermi level N(E F) is calculated. From the ratio of experimental N(E F) and the one being calculated from DFT, we obtained value of λ to be 1.84, thus placing MgB2 in the strong coupling BCS category. The electronic specific heat of MgB2 is also fitted below T c using α-model and found that it is a two gap superconductor. The calculated values of two gaps are in good agreement with earlier reports. Our results clearly demonstrate that the superconductivity of MgB2 is due to very large phonon contribution from its stretched lattice. The same two effects are obviously missing in AlB2, and hence it is not superconducting. DFT calculations demonstrated that for MgB2, the majority of states come from σ and π 2p states of boron on the other hand σ band at Fermi level for AlB2 is absent. This leads to a weak electron phonon coupling and also to hole deficiency as π bands are known to be of electron type, and hence obviously the AlB2 is not superconducting. The DFT calculations are consistent with the measured physical properties of the studied borides, i.e., MgB2 and AlB2. 相似文献
16.
E. Yu. Anikina V. N. Verbetsky A. G. Savchenko V. P. Menushenkov I. V. Shchetinin 《Inorganic Materials》2017,53(10):1009-1012
Interaction of hydrogen with the intermetallic compound Nd2Fe17 has been studied for the first time by calorimetry using a differential heat conduction calorimeter coupled to a Sieverts apparatus. Hydrogen absorption and desorption reactions were run at 200°C, and two types of data were obtained: p–C–T and ΔH–C–T (where p is the equilibrium hydrogen pressure, C = H/Nd2Fe17, ΔH is the reaction enthalpy, and T is the measurement temperature). The p–C–T curves obtained for the hydrogen absorption and desorption processes have no plateau or two-phase region, in contrast to what is characteristic of the formation of a hydride phase. At the same time, the ΔH(C) curves have a few portions where the enthalpy of reaction between hydrogen and the intermetallic compound remains constant: 0 < C < 2.0, with ΔH abs =–85.05 ± 0.65 kJ/mol H 2; 2.0 < C < 2.7, with ΔH abs =–80.64 ± 1.00 kJ/mol H2; and 1.9 < C < 2.7, with ΔH des = 76.48 ± 0.85 kJ/mol H2. The data obtained in this study suggest that positions 9e and 18g in the intermetallic compound are occupied by hydrogen in a particular order. 相似文献
17.
Mohamed Hsini Sobhi Hcini Sadok Zemni 《Journal of Superconductivity and Novel Magnetism》2018,31(1):81-87
Magnetic entropy change (?ΔS M ) of Nd0.67 Ba0.33Mn0.98Fe0.02O3 perovskite have been analyzed by means of theoretical models. An excellent agreement has been found between the (ΔSM) values estimated by Landau theory and those obtained using the classical Maxwell relation. In order to estimate the spontaneous magnetization M s pont(T), we used the mean-field theory to analyses the (ΔSM) vs. M 2 data. The obtained M s pont(T) values are in good agreement with those found from the classical extrapolation from the Arrott plots(H/M vs. M 2), confirming that the magnetic entropy is a valid approach to estimate the spontaneous magnetization in our system. At a relatively low magnetic field, a phenomenological model has been used to estimate the values of the magnetic entropy change. The results are in good agreement with those obtained from the experimental data using Maxwell relation. 相似文献
18.
L. T. Denisova L. A. Irtyugo Yu. F. Kargin V. V. Beletskii N. V. Belousova V. M. Denisov 《Inorganic Materials》2018,54(2):167-170
The Sm2Ge2O7 and Eu2Ge2O7 germanates have been prepared by solid-state reactions via multistep firing of stoichiometric mixtures of Sm2O3 (Eu2O3) and GeO2 in air at temperatures from 1273 to 1473 K. The molar heat capacity of the samarium and europium germanates has been determined by differential scanning calorimetry in the range 350–1000 K and the C p (T) data have been used to evaluate their thermodynamic properties. 相似文献
19.
We study the magnetic field vs. temperature (H – T) and pressure vs. temperature (P – T) phase diagrams of the T c ≈ 5.5 K superconducting phase in Pd x Bi2Te3 (x ≈ 1) using electrical resistivity versus temperature measurements at various applied magnetic fields (H) and magnetic susceptibility versus temperature measurements at various applied magnetic fields (H) and pressure (P). The H – T phase diagram has an initial upward curvature as observed in some unconventional superconductors. The critical field extrapolated to T = 0 K is H c (0) ≈ 6–10 kOe. The T c is suppressed approximately linearly with pressure at a rate d T c /d P ≈ ?0.28 K/GPa. 相似文献
20.
R. G. Veliev R. Z. Sadykhov E. M. Kerimova Yu. G. Asadov A. I. Dzhabbarov 《Inorganic Materials》2009,45(5):474-479
In a temperature range of 80–400 K, electrical and magnetic properties of layered compounds TlCrS2 and TlCrSe2 are investigated. It is shown that these compounds are p-type semiconductors and possess ferromagnetic ordering with T C ~90 and 105 K, respectively. 相似文献