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1.
S. Rosenkranz U. Staub A. Furrer R. Osborn P. Lacorre V. Trounov 《Journal of Alloys and Compounds》1997,250(1-2):577-580
We determined the energy splitting of the 7F1 multiplet of Eu3+ in EuNiO3 using inelastic neutron scattering. We were able to retrieve accurate values for the second order crystalline electric field parameters, which will allow a more reliable determination of the crystalline electric field potential in the RNiO3 (R=rare earth) series. This is essential for a possible observation of a charge transfer, which is proposed by one of the models describing the observed metal-to-insulator transition in these compounds. 相似文献
2.
A. Moreno-Gobbi M. P rez G. Paolini C. A. Negreira D. Garcí a J. A. Eiras 《Journal of Alloys and Compounds》2000,310(1-2):29-31
Attenuation and velocity measurements at ultrasonic frequencies were performed in two ferroelectric solid solutions with tungsten bronze structure type, SBN and PBN, as a function of temperature (from 200 to 380 K). Both materials, in polycrystalline form, presented sensitive changes in the temperature dependence curves of attenuation and velocity. One of these anomalies (at 350 K for SBN and 323 K for PBN) was associated with a second-order phase transition, confirming the ferroelectric orthorhombic–ferroelectric tetragonal phase transition suggested for both systems in this temperature range. 相似文献
3.
A thermodynamic modeling of the CeO2–CoO phase diagram was performed with recent experimental data. The excess Gibbs energies of the solution phases were described on the basis of the simple regular solution. A consistent set of optimized interaction parameters was derived for describing the Gibbs energy of each phase in this system leading to a good fit between calculation and experimental data. The liquidus, solidus, and solvus curves were calculated and also the lattice stabilities of the components were evaluated. 相似文献
4.
Masataka YamamotoSayaka Sekida Takashi Fukuda Tomoyuki KakeshitaKohki Takahashi Keiichi Koyama Hiroyuki Nojiri 《Journal of Alloys and Compounds》2011,509(34):8530-8533
Martensitic transformation in a highly ordered Fe3Pt has been investigated by magnetization and X-ray diffraction measurements. We confirmed that a new type of face-centered tetragonal (FCT) martensite phase appears below 60 K in Fe3Pt with a degree of order S = 0.88. The tetragonality c/a gradually increases with decreasing temperature, and is approximately 1.005 at 10 K. This is in contrast to the tetragonality c/a < 1 generally observed in the FCT martensite with a degree of order less than 0.8. The spontaneous magnetization increases in association with the transformation. 相似文献
5.
The high temperature phase transitions of orthorhombic La0.95MnO3 from room temperature to 1273 K were studied using high temperature XRD technique in air. Two-phase transitions were found in temperature ranges, 373–473 K and 973–1273 K, respectively. The crystal symmetry increases from orthorhombic to rhombohedral then cubic, while the second transition was not completed in the observation of the present study. The first transition could be due to the depression of Jahn–Teller distortion, while the second one could be caused by the ionic oscillation at high temperature. The lattice thermal expansion coefficients of rhombohedral La0.95MnO3 from 473 to 973 K were also calculated using lattice parameters. 相似文献
6.
The Ce2Fe17−xMnx (x = 0-2) compounds demonstrate a complex temperature dependence of the magnetocaloric effect MCE, which is inverse in a narrow temperature interval just below Néel temperature TN and normal at higher or lower temperatures. The normal MCE exhibits two peaks in the vicinity of temperatures of ferromagnetic ordering ΘT and TN for compositions x = 0-0.35, 1.3-2 or one peak near TN for antiferromagnets with x = 0.5-1. The maximal change of the peak entropy −SM is about 3 J/kg K in a field of 5 T for the compounds with x = 0-0.5 at T ∼230 K close to TN. The drastic decrease of the MCE, by half, in the Ce2Fe17−xMnx system is traceable to a decrease of the spontaneous magnetization and the helical type of magnetic states in the compounds. 相似文献
7.
Kristina ?u?ek Ro?man Darja Pe?koLarisa Suhodol?an Paul J. McGuinessSpomenka Kobe 《Journal of Alloys and Compounds》2011,509(2):551-555
Near-equiatomic Fe-Pd-based nanotubes with diameters of 200 nm and lengths of 1 μm were directly electrodeposited from a single electrolyte into polycarbonate templates. The as-deposited Fe50Pd50 nanotubes were then characterized compositionally, structurally and magnetically. The as-deposited Fe50Pd50 tubes had an fcc crystal structure and were magnetically soft (HC ≈ 10 kA/m), with the easy axis of the magnetization being parallel to the axes of the tubes. Angular-dependence measurements of the coercivity, where the hysteresis loops were measured as a function of the angle (θ) of the applied demagnetizing field, revealed a combination of magnetization reversal mechanisms, consisting of the curling mechanism, which dominates at low angles, with a transition to coherent rotation at angles ≥70°. The development of the coercivity with annealing temperature due to the L10 ordering was also investigated. For this purpose the as-deposited nanotubes were annealed at temperatures from 400 °C to 650 °C for 1 h in Ar + 7% H2 and the phase formation, the microstructure and the magnetic properties were analyzed. A maximum in the coercivity of 135 kA/m was achieved upon annealing at 550 °C. 相似文献
8.
The phase diagram in the Co–Zr system was determined using the electron probe microanalyzer (EPMA), differential thermal analysis (DTA) and X-ray diffraction (XRD) technique. The experimental results indicate that (1) the solubility region of the Co2Zr phase is from 25 to 34 at.% Zr; (2) the CoZr3 phase exists and the temperature of the peritectoid reaction (CoZr2 + (βZr) ↔ CoZr3) is about 981 °C; (3) the solubilities of Zr in the (αCo) phase and Co in the (βZr) phase are about 0.15 and 2.5 at.%, respectively. A thermodynamic assessment of the Co–Zr binary system was carried out by the CALPHAD (calculation of phase diagrams) method. The Gibbs free energies of the solution phases (liquid, fcc, bcc and hcp) were described by the subregular solution model, and those of the intermetallic compounds (Co11Zr2, Co23Zr6, Co2Zr, CoZr, CoZr2 and CoZr3) were described by the sublattice model. A proper set of the thermodynamic parameters has been derived for describing the Gibbs free energies of each phase in the Co–Zr system. An agreement between the calculated results and experimental data is obtained. 相似文献
9.
The existing Mo–Re phase diagrams are reviewed and a thermodynamic calculation of the Mo–Re binary system is undertaken. The Gibbs energies are estimated for liquid, bcc (Mo), hcp (Re), σ and χ phases. The liquid, bcc (Mo) and hcp (Re) phases are described by a regular solution model, whereas the σ and χ phases are described respectively by three-sublattice models. For the σ phase, two thermodynamic models are used for calculations and the results are compared. The models take into account the crystallographic structure and similarity between the σ and χ phases. The calculated results remove the ambiguity of the existing phase diagram data and are compared with the experimental data in the literature. 相似文献
10.
G.X. Huang L.B. Liu B.R. Jia L.G. Zhang Z.P. Jin 《Journal of Alloys and Compounds》2008,460(1-2):375-378
The Ca–Ag binary system has been assessed with CALPHAD approach based on experiment information about phase diagram and thermodynamic properties. The excess Gibbs energies of the solution phases including liquid, bcc and fcc were formulated with Redlich–Kister polynomial functions. The intermetallic compounds Ca2Ag9, Ca2Ag7, CaAg2, CaAg, Ca5Ag3 and Ca3Ag were treated as stoichiometric phases. Self-consistent thermodynamic parameters have been obtained and the calculated results agree well with most literature data. Several diagrams and tables concerning the Ca–Ag system are presented. 相似文献
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12.
Without Sr addition, the sintered La2O3 and CuO powder mixture in a mole ratio of 1:2 formed K2NiF4-structured La2CuO4 with excess CuO. When 15% of strontium was added, La2CuO4 transformed into the single perovskite La1−xSrxCuO2.5−δ phase with orthorhombic structure. As the strontium addition increased to 20%, the perovskite lattice changed from orthorhombic to tetragonal. These phase transitions may be attributed to the enhanced oxidation of the divalent cupper ions (Cu2+) to trivalent ones (Cu3+) by the strontium addition. Based on the electroneutrality in an ABO3 perovskite lattice, a divalent cation is unstable in the B-site cation sub-lattice when the A-site is occupied by a trivalent cation such as La3+. As strontium was added into the A-site cation sub-lattice, the oxidation of Cu2+ ion into trivalent Cu3+ ion was enhanced. The increase of Cu3+ concentration strengthened the electrostatic bonding (ESB) of copper ions with their neighboring anions. Consequently, the symmetrical tetragonal Sr-doped lanthanum copper oxide was obtained. 相似文献
13.
Byung Joo Park Sung Woo Sohn Won Tae Kim Do Hyang Kim 《Journal of Alloys and Compounds》2009,483(1-2):260
Structural evolution during heat treatment of melt spun Ti36Y20Al24Co20 alloy was studied using differential scanning calorimetry, X-ray diffractometry and transmission electron microscopy. The as-melt spun Ti36Y20Al24Co20 specimen showed a hierarchical complex microstructure consisting of Ti-rich and Y-rich amorphous phases and crystallized with two-step process. Crystallization in the phase separated two phase mixture took place in a confined mode due to different thermal stability and complex microstructure, resulting in various nano-scaled microstructural formation ranging from fine distribution of crystalline particles in amorphous matrix to fine distribution of amorphous particles in crystalline matrix. 相似文献
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15.
A. Dnni L. Keller H. Kitazawa J. Prchal P. Fischer 《Journal of Alloys and Compounds》2008,464(1-2):67-74
By using powder neutron diffraction we provide a detailed structural and magnetic investigation of the pseudo-ternary compound TbPd0.9Ni0.1Al with hexagonal ZrNiAl-type crystal structure and disorder of palladium and nickel atoms on two crystallographic sites. We provide experimental evidence for the occurrence of an isostructural phase transition in TbPd0.9Ni0.1Al at 157 K, which is affected by structural disorder compared to that observed in TbPdAl. In TbPd0.9Ni0.1Al the step of the c/a ratio at the first-order phase transition appears about four times smaller than in TbPdAl. TbPd0.9Ni0.1Al undergoes two successive magnetic phase transitions at TN1=41 K and TN2≈21.5 K. Two third of non-frustrated ordered Tb moments form commensurate antiferromagnetic chains () and coexist with one third of frustrated ordered Tb moments, which change from a commensurate structure () between TN2 and TN1 to an incommensurate structure () below TN2. Due to the strong magneto-crystalline anisotropy all ordered Tb moments stay perpendicular to the ab-plane and reach at 1.5 K saturation values of 8.6 (2) μB (non-frustrated) and 7.2 (2) μB (frustrated). The symmetry of the magnetic structure of TbPd0.9Ni0.1Al is lower than that of TbNiAl. 相似文献
16.
Mahmood Mamivand Mohsen Asle Zaeem Haitham El Kadiri Long-Qing Chen 《Acta Materialia》2013,61(14):5223-5235
The allotropic phase transformation in zirconia from the tetragonal to monoclinic double lattices is known to occur by a martensitic twinning mechanism which shows a complex dependence on temperature, stress and environment. This paper is concerned with the development of a phase field model which accounts for the main metallurgical mechanisms governing this martensitic transition. The symmetry reduction and orientation relationship between the parent and product phases were simulated using several non-conserved order parameters representing different transformation paths. Inhomogeneous and anisotropic elastic properties were considered to determine the resultant elastic stresses. Governing equations of the tetragonal-to-monoclinic transformation were solved in a finite element framework under a variety of initial and boundary conditions. It was shown that applying different initial conditions, such as seed embryo or random, did not change the twinning patterns or the final volume fractions of the parent and product phases after the relaxation period. On the other hand, enforcing different boundary conditions resulted in completely different twinning patterns and phase volume fractions. The model was able to predict both the “V” shape morphology of twinning and the surface stress relief with “gable roof” patterns, which were observed by transmission electron microscopy and atomic force microscopy to be characteristic of the tetragonal-to-monoclinic transition. 相似文献
17.
柳林 《中国有色金属学会会刊》2002,12(1):62-66
1 INTRODUCTIONRefractorymetalsilicideshaveattractedanin creasingattentioninrecentdecadesbecauseoftheirunique combinationofmechani 相似文献
18.
The structure and magnetic properties of Nd1−xYxMn2Ge2 (0.0≤x≤0.6) were studied by X-ray powder diffraction and magnetization measurements. All compounds crystallize in the ThCr2Si2-type structure with space group I4/mmm. Substitution of Y for Mn led to a linear decrease in the lattice constants and the unit cell volume. Increasing substitution of Y for Nd in NdMn2Ge2 shows a depression of ferromagnetic ordering and the gradual development of antiferromagnetic ordering. 相似文献
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A number of thermodynamic optimisations of the Ni–V system have been carried out using experimental phase diagram and thermodynamic data available from the literature. In each optimisation, a different model was used to describe the thermodynamic properties of the sigma phase. The results of the optimisations have been compared with each other and their shortcomings discussed. 相似文献