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91.
Zhang J Duan Z He D Dai S Zhang L Hu L 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2005,62(4-5):831-834
Up-conversion luminescence properties of a Tm3+/Yb3+ codoped oxyfluoride glass-ceramics under 980 nm excitation are investigated. Intense blue emission centered at 476 nm, corresponding to 1G4-->3H6 transitions of Tm3+ was simultaneously observed in the transparent oxyfluoride glass ceramics at room temperature. The intensity of the blue up-conversion luminescence in a 1 mol% YbF3-containing glass-ceramic was found to be about 40 times stronger than that in the precursor oxyfluoride glass. The reason for the intense Tm3+ up-conversion luminescence in the oxyfluoride glass-ceramics is discussed. The dependence of up-conversion intensities on excitation power and possible up-conversion mechanism are also evaluated. 相似文献
92.
Thermostimulated luminescence (TSL) of PbWO4, Bi2WO6, and Y2WO6 ceramics on x-ray excitation is investigated. The spectral luminosity of the thermostimulated luminescence is analyzed. The thermal activation energies conforming to the corresponding thermostimulated luminescence peaks are determined. It is established that on emptying trapping centers radiative recombination occurs at the intrinsic-luminescence centers associated with tungsten-oxygen complexes WO4
2–. 相似文献
93.
Explicit equations correlating oxygen nonstoichiometry to oxygen partial pressure and temperature are important for applications of perovskite-type ceramics as membranes, adsorbents and catalysts in various chemical reaction and separation processes. A semi-empirical equation for oxygen nonstoichiometry on perovskite-type ceramics is reported in this paper. Though derived from the results of a point defect model on a perovskite-type ceramic material, La0.1Sr0.9Co0.5Fe0.5O3−δ, this equation describes very well the experimentally measured oxygen nonstoichiometry data for two perovskite-type ceramics measured in this work and three perovskite-type ceramics reported in the literature. The major advantage of this semi-empirical equation lies in its simplicity, explicitness and accuracy. This equation is coupled with oxygen permeation equation to predict oxygen permeation current density through two perovskite-type ceramic membranes. The predicted data agree very well with the results reported in the literature using a complex defect reaction model. 相似文献
94.
J.H. Harding 《Interface Science》2003,11(1):81-90
This article discusses grain boundary diffusion in ceramics. It gives a brief review of the experimental data available for ionic oxides and the problems of interpretation associated with it. The fundamental differences between grain boundary diffusion in metals and ceramics are noted. Calculations of the segregation of defects and impurities to grain boundaries are discussed together with methods of calculating diffusion coefficients in these boundaries. New results for alumina and chromia are presented. The problem of defining a grain boundary width is discussed with respect to new calculations on nickel oxide. 相似文献
95.
The dependence of loss tangent (tanδ) and relative permittivity (εr) on temperature and frequency has been reported for Na2-XKXTi3O7 (with X=0.2, 0.3, 0.4) ceramics. The losses are characteristic of dipole mechanism and electrical conduction. The peaks of εr at high temperature indicate a possible ferroelectric phase transition for all three compositions. The results of a.c. conductivity studies on the same samples have also been reported. The corresponding ln(σT) versus 1000/T plots have been divided into five regions namely I, II, III, IV and V. The various conduction mechanisms in the different regions have been stressed. Furthermore, the log(σ) versus frequency plots for all the above samples reveal that the electronic hopping (polaron) conduction, which diminishes with the rise in temperature, is dominant in the lower temperature region. The interlayer ionic conduction seems to play a major role in conduction towards higher temperature. 相似文献
96.
97.
Using DSC technique, the chemical interaction in Bi2O3+MO2 mixtures resulting the Bi12MO20 phase, (M=Ti, Ge and Si) was monitored. Kinetic parameters for the primary stage of interaction were yielded by the non-isothermal method of kinetic evaluation of experimental heat flux DSC curves. The model of three-dimensional diffusion according to Jander was fitted as the best in a statistical sense.
Zusammenfassung Mittels DSC wurde die Bildung von Bi12MO20-Phasen aus Bi2O3+ MO2-Gemischen (mitM= Ti, Ge uns Si) untersucht. Die kinetischen Parameter für den ersten Schritt der Reaktion erhielt man mittels einer nichtisothermen Methode der kinetischen Auswertung der experimentellen Wärmefluß-DSC-Diagramme. Als bestes Modell zur Beschreibung des Vorganges ergab sich das dreidimensionale Diffusions modell von Jander.相似文献
98.
99.
100.
P.A. Márquez Aguilar M. Vlasova D. Mayorga Cruz V. Stetsenko A. Ragulya 《Optics & Laser Technology》2010,42(1):172-179
Using electron microscopy and X-ray microanalysis, the formation of tracks by laser processing of AlN:Y2O3 ceramic surfaces was investigated. The main process of channel formation is the decomposition of aluminum nitride (AlN). Due to aluminothermic reduction of Y2O3, the metallization of channel surfaces occurs. The main products of ablation are Al2O3, AlN, and AlON. 相似文献