ISSN:
1572-8943
Schlagwort(e):
DTA
;
high temperature superconductors
;
phase diagrams
;
TG
;
thermal analysis
Quelle:
Springer Online Journal Archives 1860-2000
Thema:
Chemie und Pharmazie
Notizen:
Abstract With the discovery of high temperature superconductivity an extraordinary field for investigations on new materials containing up to (more than) 8 or 9 components has been open. But, in addition to problems specifically related to superconductivity, we are faced with a prelimary difficulty: the preparation of well defined compounds which may have reproducible properties. This difficulty is smoothed out when the phase relations in the relevant systems are known. Differential Thermal Analysis (DTA) contributes to their establishment. However, in multicomponent systems, an isopletic line is expected to intercept various boundary surfaces and the analysis is obviously complicated, compared to low order systems. In addition, by the nature of high temperature superconductors the oxygen partial pressure used for their preparation is an important thermodynamic parameter which contributes to fix the oxygen content in the solid state. During heat treatments, the composition of the systems may change, due to oxygen or volatile oxides (Tl2O3, PbO2 or HgO) release. A permanent composition control then requires thermogravimetric (TG) measurements associated to DTA. This paper attempts to demonstrate the efficiency of the assembly DTA/TG for the study of high temperature superconductors. Going beyond the frame of preparation and quality control, the system is also particularly useful for kinetic studies. Examples will be principally in the (Tl,Pb)-(Ba,Sr)-Ca-Cu-O systems.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1007/BF01979505
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