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J. Karpinski S. Rusiecki E. Kaldis B. Bucher E. Jilek 《Physica C: Superconductivity and its Applications》1989,160(5-6):449-457
The P-T-x phase diagram of the pseudobinary system (Y-Ba-Cu-O)-O2 has been further investigated in the oxygen pressure range between 1 and 3000 bar. The stability ranges of the phases YBa2Cu4O8 (124), YBa2Cu3.5O7.5−x (123.5) and YBa2Cu3O7−x (123) have been determined. Long duration experiments showed that the 123 phase is not stable at least down to 7 bar≤P≤20 bar oxygen and 900°C. It is not clear whether at lower pressures and temperatures the 123 phase is thermodynamically stable or metastable due to low reaction rates. In the presence of excess CuO, the 124 is the stable phase. The melting of 124 pellets at PO2=2800 bar shows that even at this pressure the 124 compound melts incongruently. Using the phase diagram data we could change the Tc of 123.5 from 16 to 70 K by varying systematically the nonstoichiometry. Due to a narrow homogeneity range the Tc of 124 remained constant but is different for powder pellets (81 K) and for crystals (70 K), probably due to the influence of the flux. Single crystals of both 124 and 123.5 with dimensions up to 4 mm were grown from the flux under high oxygen pressure. 相似文献
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Gunnar Myhre Frode Stordal Ingvil Gausemel Emanuel Mahieu 《Journal of Quantitative Spectroscopy & Radiative Transfer》2006,97(3):317-331
We estimate a current direct radiative forcing due to CFC-12 of 0.18 Wm-2, which is likely to be the peak radiative forcing for CFC-12. Global measurements of CFC-12 show at present an almost negligible trend for CFC-12 and measurement in an industrialized region show evidence that the peak concentration is reached. It is expected that concentration of CFC-12 in industrialized regions begins to decline 1-3 years before the global concentration.Our radiative forcing calculations are based on a line-by-line model appropriate for simulation of global mean radiative forcing, including clouds and stratospheric temperature adjustment. The radiative forcing of 0.33 Wm-2/ppbv is close to earlier published results for this compound. New spectroscopic measurements for CFC-12 are performed and compared to previously published results. 相似文献
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Octaethyltetraoxaporphyrin-Dikation – Pendant des Octaethylporphyrins in der Tetraoxaporphyrin-Reihe
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