Shuigen HUANG
,
Lin LI
,
J.Vleugels
,
O.V.D.Biest
,
Peiling WANG
材料科学技术（英文）
The ZrO2-CeO2-Al2O3 system has been assessed with the CALPHAD (Calculation of Phase Diagrams) technique using the PARROT procedure. The experimental information on the ZrO2 -Al2O3, Al2O3-CeO2 systems as well as the isothermal sections of the ternary system at 1673 K and 1873 K is well reproduced. According to the assessed isothermal section at 1723 K, no alumina dissolves into the tetragonal zirconia phase. Specimens with different alumina content are fabricated from commercial 12 mol pct CeO2-stabilized ZrO2 powder (12Ce-ZrO2). The thermodynamic properties are consistent with the observed microstructure, which present a combination of tetragonal phase and alumina grains.
关键词:
Ce-TZP
,
null
,
null
Shuigen HUANG
,
Lin LI
,
J.Vleugels
,
O.V.D.Biest
材料科学技术（英文）
The phase constitution of a composite consisting of 12 at. pct CeO2-3 at. Pct Y2O3-ZrO2/2.5 wt pct Al2O3 (3Y12Ce2.5Al) was determined by thermodynamic calculation. It is a combination of 36.9 at. pct cubic phase and 63.1 at. pct tetragonal phase at 1450℃. Green compacts were fabricated by cold isostatic pressing with powder synthesized by coating technique, and pressureless sintered at 1450℃. The fracture toughness and Vickers hardness, evaluated by the micro-indentation method, are 2.02 MPa·m1/2 and 11.395 GPa, respectively. The addition of 3 at. pct Y2O3 to 12 at. Pct CeO2-ZrO2 ceramic leads to drastically decrease in toughness compared to composites without yttria stabilizer. No monoclinic phase is detected on the surface of all the ground samples. The high content of cubic phase and lack of phase transformation can be attributed to the low toughness based on the thermodynamic prediction.
关键词:
Thermodynamics
,
null
,
null
Shuigen HUANG
,
Lin LI
,
O.V.D.Biest
,
J.Vleugels
,
Peiling WANG
材料科学技术（英文）
Using compound energy model (CEM), the thermodynamic properties of and were evaluated. The evaluation was based on the optimization of ZrO2-CeO2 and ZrO2-CeO1.5 systems, as well as the miscibility gap in CeO1.5-CeO2 system. Except the cubic fluorite structure phase assessed with compound energy model, all the other solution phases were assessed with subsitutional solution model. The model parameters were evaluated through fitting the selected experimental data by means of thermodynamic optimization. A set of parameters with thermodynamics self-consistency was obtained and satisfactorily described the complex relation between y in and the partial pressure of oxygen at different temperatures, also the interdependence among miscellaneous factors such as temperature, oxygen partial pressure, the reduction amount of CeO2 as well as the nonstoichiometry in cubic phase . The calculated results seem to be reasonable when put into the explanation of pressureless sintering of CeO2-stabilized ZrO2 powder compacts at a controlled oxygen partial pressure.
关键词:
Zirconia
,
null
,
null
,
null
Journal of Alloys and Compounds
The influence of magnetic fields on the mechanical loss (Q(-1)) of Terfenol-D/PbZr(0.52)Ti(0.48)O(3)/Terfenol-D three-layer laminated composites is investigated systemically using the technique for measuring the resonance magnetoelectric (ME) effect. The results indicate that Q(-1) varies non-monotonically with dc magnetic fields and shows a maximum near 500 Oe for all the samples with different layer thickness ratios (n) of Terfenol-D (Tb(0.3)Dy(0.7)Fe(1.92)). Considering various kinds of mechanical energy dissipation, it is found that Q(-1) is mainly dominated by the mechanical damping due to the domain wall motion in Terfenol-D under the actions of dc and ac magnetic fields as well as the stress at the interface. In addition, the effect of eddy current losses on the energy dissipation of the system is also discussed. (C) 2011 Elsevier B.V. All rights reserved.
关键词:
Magnetoelectric composite;Mechanical energy dissipation;Domain wall;motion;magnetomechanical damping capacity;terfenol-d;magnetostriction;alloys;tb0.27dy0.73fe2;tb0.3dy0.7fe1.95
Radiation Effects and Defects in Solids
The empirical superposition model has been used to analyse the zero-field splitting of 3d5(Mn2+, Fe3+) ions in crystals with approximately C3v symmetry. The negative signs of intrinsic parameters b2BAR(R0) for these crystals are the same as the normal b2BAR(R0) which is obtained from the 3d' ions in many oxygen octahedra. The magnitude of b2BAR(R0) for Mn2+ or Fe3+ ion in the case of isocharge substitution is consistent with the respective normal value of Mn2+ or Fe3+ ion. Whereas in the case of charge misfitting substitution, the small disparity of b2BAR(R0) is found between the calculated and normal values. This can be attributable to the local lattice relaxation caused by the fact that the interacting forces between impurity and ligands are different from those of host crystals. It appears that the anomaly related to the signs of b2BAR in Al2O3:Fe3+, MgTiO3:Mn2+ and MgTiO3:Fe3+ crystals pointed out by some researchers does not exist and the empirical superposition model is applicable to 3d5 ions in C3v symmetry.
关键词:
electron paramagnetic resonance;superposition model;mn2+;fe3+;al2o3;mgtio3;linbo3;litao3;sites;epr
Science in China Series a-Mathematics Physics Astronomy
The complete strong-field-matrices for d2,8(C3v*) ions are constructed within an O(h)- point-group representation. Based on the eigenvalues and eigenvectors of these matrices, a complete-configuration-mixing EPR theory is established for Ni2+ ions in CsMgX (X = Cl, Br,I) kind crystals, and accordingly, a uniform calculation is performed for the optical absorption spectrum, the zero-field-splitting and Zeeman splitting of the ground state, the EPR parameters D and g and the EPR conditions (B,h-nu) of Ni2+ impurity ions in a CsMgCl3 crystal. The results are in very good agreement with the experimental, thus a uniform theoretical interpretation is achieved for the optical and magnetic properties of Ni2+:CsMgCl3 for the first time.
关键词:
complete strong-field-matrix for d2,8(c3v-star);complete-configuration-mixing epr theory;csmgcl3;ni2+;optical and;magnetic properties;strong-field scheme;spectrum
Physica B-Condensed Matter
The spin-lattice coupling coefficients G11 and G44 for InP:Fe3+ and GaP:Mn2+ crystals have been calculated from the expressions based on the spin-orbit coupling mechanism. The results, as well as those for GaP:Fe3+ in my previous paper, show good agreement with the experimental findings. It appears that this mechanism is applicable to the explanations of the spin-lattice coupling coefficients for 3d5 ions in III-V compounds. The disparity between theory and experiment for the coefficients G11 and G44 of GaAs:Fe3+ crystals is discussed.
关键词:
transition-metal impurities;electronic states;inp
Journal of Luminescence
In this paper, we give an alternative suggestion that both the observed optical and electron paramagnetic resonance (EPR) spectra of Yttrium oxide (Y2O3):V3+ are attributed to V3+ ions at the S-6 site Of Y2O3. This suggestion is different from the opinion in the previous paper that the optical and EPR spectra are attributed to V3+ ions at the C, and S-6 sites, respectively. From the suggestion, the optical band positions and spin-Hamiltonian parameters are calculated by diagonalizing the complete energy matrix for 3d(2) ions in trigonal symmetry. The results are in good agreement with the experimental values, suggesting that both the observed optical and EPR spectra in Y2O3 :V3+ may be due to V3+ at S-6 site Of Y2O3 crystal. (c) 2008 Elsevier B.V. All rights reserved.
关键词:
optical spectra;EPR spectra;crystal-field theory;V3+;Y2O3;spin-hamiltonian parameters;paramagnetic-resonance;energy-levels;cr3+;ions;field;3d(8)
