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881.
882.
J.?R.?Tolchard J.?E.?H.?Sansom P.?R.?SlaterEmail author M.?S.?Islam 《Journal of Solid State Electrochemistry》2004,8(9):668-673
Recently, high oxide ion conduction has been observed in the apatite-type systems La9.33+x(Si/Ge)6O26+x/2, with conductivities approaching and even exceeding that of yttria-stabilized zirconia. The Ge-based phases have been reported to suffer from Ge loss and undergo irreversible structural changes on sintering at the high temperatures required to obtain dense pellets. In this paper we discuss doping studies (Ba, Bi for La) aimed at stabilizing the hexagonal apatite lattice to high temperature, and/or lowering the synthesis and sintering temperatures. The results show that doping with Ba helps to stabilize the hexagonal lattice at high temperatures, although Ge loss appears to still be a problem. Conductivity data show that, as previously reported for the Si-based systems, non-stoichiometry in the form of cation vacancies and/or oxygen excess is required to achieve high oxide ion conduction in these Ge-based systems. Neutron diffraction structural data for the fully stoichiometric phase La8Ba2Ge6O26 shows that the channel oxygen atoms show little anisotropy in their thermal displacement parameters, consistent with the low oxide ion conductivity of this phase. Bi doping is shown to lower the synthesis and sintering temperatures, although the presence of Bi means that these samples are not stable at high temperatures under reducing conditions.Presented at the OSSEP Workshop Ionic and Mixed Conductors: Methods and Processes, Aveiro, Portugal, April 10–12, 2003 相似文献
883.
884.
885.
Claiser N Souhassou M Lecomte C Gillon B Carbonera C Caneschi A Dei A Gatteschi D Bencini A Pontillon Y Lelièvre-Berna E 《The journal of physical chemistry. B》2005,109(7):2723-2732
High-resolution X-ray diffraction and polarized neutron diffraction experiments have been performed on the Y-semiquinonate complex, Y(HBPz3)2(DTBSQ), in order to determine the charge and spin densities in the paramagnetic ground state, S = (1/2). The aim of these combined studies is to bring new insights to the antiferromagnetic coupling mechanism between the semiquinonate radical and the rare earth ion in the isomorphous Gd(HBPz3)2(DTBSQ) complex. The experimental charge density at 106 K yields detailed information about the bonding between the Y3+ ion and the semiquinonate ligand; the topological charge of the yttrium atom indicates a transfer of about 1.5 electrons from the radical toward the Y3+ ion in the complex, in agreement with DFT calculations. The electron density deformation map reveals well-resolved oxygen lone pairs with one lobe polarized toward the yttrium atom. The determination of the induced spin density at 1.9 K under an applied magnetic field of 9.5 T permits the visualization of the delocalized magnetic orbital of the radical throughout the entire molecule. The spin is mainly distributed on the oxygen atoms [O1 (0.12(1) mu B), O2(0.11(1) mu B)] and the carbon atoms [C21 (0.24(1) mu B), C22(0.20(1) mu B), C24(0.16(1) mu B), C25(0.12(1) mu B)] of the carbonyl ring. A significant spin delocalization on the yttrium site of 0.08(2) mu B is observed, proving that a direct overlap with the radical magnetic orbital can occur at the rare earth site and lead to antiferromagnetic coupling. The DFT calculations are in good quantitative agreement with the experimental charge density results, but they underestimate the spin delocalization of the oxygen toward the yttrium and the carbon atoms of the carbonyl ring. 相似文献
886.
887.
K. Jungmann P. E. G. Baird J. R. M. Barr C. Bressler P. F. Curley R. Dixson G. H. Eaton A. I. Ferguson H. Geerds V. W. Hughes J. Kenntner S. N. Lea F. Maas M. A. Persaud G. zu Putlitz P. G. H. Sandars W. Schwarz W. T. Toner M. Towrie G. Woodman L. Zhang Z. Zhang 《Zeitschrift für Physik D Atoms, Molecules and Clusters》1991,21(3):241-243
The 12 S 1/2(F=1)?22 S 1/2(F=1) energy interval in muonium has been investigated by Doppler-free two-photon laser spectroscopy. The transition was observed by uniquely identifying and counting the muons released after the photoionization of the 2S state by the same laser field. The measured transition frequency of 2455 528016(58)(43) MHz is in good agreement with QED calculations. The experiment can be interpreted as a test of the Lamb shift contributions at the 1% level. The method is also well suited for a precise determination of the mass of the positive muon in a muoniumhydrogen isotope shift measurement. 相似文献
888.
H. Kawaguchi S. Kataiwa T. Mita Y. Ohtsuka T. Takeuchi S. Kobayashi 《Colloid and polymer science》1990,268(12):1167-1173
Dichlorophene was used as a model drug. Drug-carrying latex particles were prepared by soap-free emulsion copolymerization of dichlorophene acrylate with some hydrophilic methacrylate comonomers. The comonomers used affected not only the structure and colloidal stability of particles, but also the drug-activity of particles. Preliminary study of the drug activity revealed that highly hydrophilic latex particles were very stable and too inactive to be engulfed by amoebae and kill them. On the contrary, less hydrophilic particles carrying a large amount of drug can be an effective device to release drugs at a moderate rate to fight against extracelluar targets such as parasites. 相似文献
889.
V. M. Zhulin N. N. Malysheva Z. G. Makarova E. M. Klimov N. K. Kochetkov 《Russian Chemical Bulletin》1990,39(9):1940-1942
The polycondensation of 1,2-0-exo-cyanethylidene-4,6-di-0-acetyl-3-0-trityl--D-glucopyranose (I) was accomplished in the presence of triphenylmethylium perchlorate in CH2Cl2 under the pressure of 14 kbar. The reaction was performed in the frozen solution after the phasic transition of the system, and led to the product of polycondensation which, after the removal of the protecting groups, gave the exactly regio- and stereo-regular -(1–3)-D-glucan.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 9, pp. 2129–2132, September, 1990. 相似文献
890.