F. Zhang1)
,
X. D. Sun1)
,
J. You2)
,
Z. Zhang2)
,
L. X. Ding3)and Y. M. Wang3)1) School of Materials and Metallurgy
,
Northeastern University
,
Shenyang 110006
,
China2) Liaoning Analyzing and Testing Research Center
,
Shenyang 110015
,
China3) Department of Materials
,
School of Mechanical Engineering
,
Shenyang University
,
Shenyang 110044
,
China
金属学报(英文版)
Synthesis of a m m oniu m alu min u m carbonate hydroxide ( A A C H) w as investigated usinga m m oniu m alu min u m sulfate and a m moniu m hydro carbonate as the starting m aterials . Itw as found that A A C Hcan be synthesized by adding a m m oniu m alu m inu m sulfate solution torapidly stirred a m moniu m hydro - carbonate solution at a tem perature of 30 ℃. A A C Hcantransfor m to α Al2 O3 co m pletely by calcining at 1100 ℃ for 1 hour , and the obtained po w ders , with a particle size of 100 n m , can be sintered to 98 99 % relative density at 1500 ℃for 2 hours .
关键词:
a m moniu m alu m inu m carbonate hydroxide
,
null
,
null
,
null
Journal of Alloys and Compounds
The off-center displacement of Ni3+ ion in SrO crystal is investigated by analyzing its anisotropic g factors g(//) and g(perpendicular to) by using the perturbation formulas of the g factors for a 3d(7) ion in axial (tetragonal or trigonal) symmetry. In these formulas, the contributions to the g factors from the mixture of different energy states, low symmetry distortion and covalency effect are included and the parameters related to these effects can be obtained from the optical spectral and local structural parameters of the studied system. Based on the studies, it is found that the Ni3+ impurity may take an off-center displacement by about 0.23 Angstrom along the [1 1 1] direction and result in a trigonally distorted [NiO6](9-) cluster. Interestingly, the observed Ni3+ center has the unusual T-4(1) ground orbital triplet due to the weak crystal field of the host SrO, which is different from the usual E-2 ground orbital doublet for Ni3+ under strong octahedral fields. The reasonableness of the results is discussed. (C) 2003 Elsevier B.V. All rights reserved.
关键词:
defect structure;electron paramagnetic resonance;crystal- and;ligand-field theory;Ni3+;SrO;atomic screening constants;transition metal ions;paramagnetic-resonance;spin resonance;superposition model;scf;functions;crystals;oxide;co2+;epr
Journal of Physics and Chemistry of Solids
The tetragonal distortion for the tetragonal V2+-V-M center in KBr:V2+ crystal is estimated by analyzing its EPR data from two theoretical models, one is the two spin-orbit (S.O.) parameter model where the contributions to EPR parameters from both the S.O. coupling of the central metal ion and that of the ligands are considered and another is the conventional one-S.O.-parameter model where only the contribution from the S.O. coupling of the central metal ion is included. The result from the two-S.O.-parameter model is more than ten times that of the one-S.O.-parameter model. The reasonableness of the former is discussed. (C) 1998 Elsevier Science Ltd. All rights reserved.
关键词:
inorganic compounds;crystal fields;defects;electron paramagnetic;resonance (EPR);epr parameters;transition;ions
Journal of Magnetism and Magnetic Materials
The local structure and the electron paramagnetic resonance (EPR) g factors g(parallel to), g(perpendicular to) and the hyperfine structure constants A(parallel to) and A (perpendicular to) for the trigonal Co2+ center in K4CdCl6 are theoretically investigated by using the perturbation formulas of the EPR parameters for a 3d 7 ion in trigonal symmetry based on the cluster approach. In these formulas, the contributions to the EPR parameters arising from the admixture of different energy levels, covalency effect and low symmetry distortion are included. The parameters related to the above effects are obtained from the optical spectral data and the local geometrical relationship of the studied system. By analyzing the EPR spectra, we find that the impurity-ligand bonding angle beta (approximate to53.54degrees) related to the C-3-axis in the Co2+ impurity center is smaller than the corresponding metal-ligand bonding angle beta(H) (approximate to 54.90degrees) in the host K4CdCl6. From the difference Deltabeta between the bonding angle beta (or beta(H)) and the corresponding angle beta(0) (approximate to54.74degrees) in cubic symmetry, the chlorine octahedron changes from compression (Deltabeta(H) = beta(H) - beta(0) > 0) in the host to elongation (Deltabeta = beta - beta(0) < 0) in the impurity center. The calculated EPR parameters, especially the anisotropies of the g and A factors for K4CdCl6: Co2+ based on the angle beta show good agreement with the observed data. The theoretical studies on the local structure for Co2+ in K4CdCl6 would be helpful to understand the structure properties for the equivalent octahedral transition-metal M site in the isostructural A(3)M'MO6 compounds. (C) 2003 Elsevier B.V. All rights reserved.
关键词:
defect structure;electron paramagnetic resonance;crystal- and;ligand-field;Co2+;K4CdCl6;atomic screening constants;magnetic-properties;superposition model;rh(iii) compounds;scf functions;sr3mrho6 m;cr3+ ions;crystals;impurities;transition
Chinese Physics Letters
The electron paramagnetic resonance spectra of trigonal Mn(2+) centers in ZnNbOF(5)center dot 6(H(2)O) and CoNbOF(5)center dot 6(H(2)O) crystals are studied on the basis of the complete energy matrices for a d(5) configuration ion in a trigonal ligand field. It is demonstrated that the local lattice structure around a trigonal Mn(2+) center has an elongation distortion along the crystalline c(3) axis, and when Mn(2+) is doped in the ZnNbOF(5)center dot 6(H(2)O) and CoNbOF(5)center dot 6(H(2)O) crystals, there is a similar local distortion. From the EPR calculation, the local lattice structure parameters for trigonal Mn(2+) centers in ZnNbOF(5)center dot 6(H(2)O) and CoNbOF(5)center dot 6(H(2)O) are determined.
关键词:
phase-transition;ions;complexes;crystals;spectra;fe-3+;epr
