The combined effects of both oxygen partial pressure (P-O2) and temperature on the Tl2Ba2CuOx-->Tl2Ba2CaCu2Ox transformation have been investigated for the 2Tl:2Ba:1Ca:2Cu nominal composition in an open reactor. Besides the 2201 and 2212 phases, no other superconducting phases have been observed in the temperature range 860-930 degrees C and the P-O2 range 2 x 10(-5)-1 atm investigated. There is evidence that P-O2 plays a key role in the 2201-->2212 transformation. A nearly pure 2212 single phase is obtained in very narrow temperature ranges depending upon P-O2. Lower temperature intervals are always associated with lower P-O2 values. This behaviour points to the rapid kinetics of 2212 formation, probably assisted by the presence of a liquid phase. The temperature shift, associated with the predominant intervals of the 2212 phase, is clearly related to the solidus temperature variations (upon P-O2) of the superconducting thallium phases.
Effect of oxygen partial pressure on the Tl(2)Ba(2)CuO2->Tl2Ba2CaCu2Ox transformation
MALANDRINO, Graziella;CONDORELLI, Guglielmo Guido;
1996-01-01
Abstract
The combined effects of both oxygen partial pressure (P-O2) and temperature on the Tl2Ba2CuOx-->Tl2Ba2CaCu2Ox transformation have been investigated for the 2Tl:2Ba:1Ca:2Cu nominal composition in an open reactor. Besides the 2201 and 2212 phases, no other superconducting phases have been observed in the temperature range 860-930 degrees C and the P-O2 range 2 x 10(-5)-1 atm investigated. There is evidence that P-O2 plays a key role in the 2201-->2212 transformation. A nearly pure 2212 single phase is obtained in very narrow temperature ranges depending upon P-O2. Lower temperature intervals are always associated with lower P-O2 values. This behaviour points to the rapid kinetics of 2212 formation, probably assisted by the presence of a liquid phase. The temperature shift, associated with the predominant intervals of the 2212 phase, is clearly related to the solidus temperature variations (upon P-O2) of the superconducting thallium phases.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
