Effect of chemical degradation on superconducting properties of the HTSC ceramics

Abstract

The effect of humid atmosphere (59 and 86~o) on phase composition and properties of YBa2Cu307 _ ~ powder and ceramics prepared by hot pressing has been studied. It has been found that with increase of water content in the powder to 1-6 mass.~o the superconducting properties of the corresponding ceramics gradually improve; on further increase of the water content the ceramics degrade resulting in a complete loss of superconductivity. The observed phenomenon can be explained by a plastifying effect of water on the powder by hot pressing on the one hand and by a solid-phase reaction of the products of decomposition (1-2-3) at a high temperature annealing, on the other.

A note on the peculiarities of producing of high-temperature super-conducting polymer–ceramic composites

“…For the compositions with polyvinyl alcohol, the observed decrease of T i by 5 • C speaks of the possible interaction of some fragments of the polymeric chain with the surface of the ceramic. In this case, OH groups, like in water [6], alcohol or weak acids [7], while reacting distort the orthorhombic phase in nearby-surface layers of the ceramic's grain, and thus decreasing the critical temperature of superconducting transition. Table 2 Thermo stability of the polymeric binders and of SC compositions based on them (T press = 130 • C, τ press = 4 min) 1.…”

Intercalated Nanocomposites Based on High-Temperature Superconducting Ceramics and Their Properties

“…For the compositions with polyvinyl alcohol the observed decrease of T c by five degrees speaks to the possible interaction of some fragments of the polymeric chain with the surface of the ceramic. In this case OH groups, like in water, alcohol or weak acids [32], while reacting distort the orthorhombic phase in nearby-surface layers of the ceramic’s grain, and thus decreasing the critical temperature of the superconducting transition. For the polyformaldehyde composition, the considerable T c decrease can be explained by the high inclination of polyformaldehyde towards thermo-oxidative destruction, which enhances the consumption of oxygen in the ceramic.…”

The route to the YBCO/Ag composite: structural and electrical properties

“…This is probably due to a partial decomposition under a moist atmosphere during the prolonged storage time. However, it is known [6] that such powders restore their properties after the heat treatment during the sample preparation process. The first heating stage was carried out at 260…”