SUPERCONDUCTIVE CERAMICS OBTAINED WITH SOL–GEL METHODS

Abstract

Several sol–gel routes have been considered, studied and developed to produce large quantities of granulates which can be processed to obtain ceramics having good superconducting characteristics. In the considered process a mixture of commercial nitrates is atomized, at room temperature, in a solution 1:1 of Primene JMT and benzene, and a pale blue gel of the starting elements is suddenly formed. The granulates obtained are free flowing, very reactive and well suited for pressing. For their intrinsic characteristics they could be very good precursors for the production of large quantities of superconductive ceramics in different forms. The precipitated gel is dried, calcined, pressed in the form of cylindrical pellets which are sintered up to 960°C. No grinding or different thermal treatments are needed. The sintered material has low electric resistance, shows a clear Meissner effect and has a transition temperature of between 91 and 95 K.