NON-ISOVALENT METAL SUBSTITUTION FOR BISMUTH, STRONTIUM, CALCIUM, ANDCOPPER IN BI-BASED 2212 SUPERCONDUCTING CERAMICS

The aim of this paper is to investigate the influence of non-isovalent alkali (Li, Na, K and Ca) substitution in Bi2Sr2CaCu2O8, in particula r on its synthesis conditions and on their resistive and thermopower e lectrical properties. Liquid phase development during the synthesis pr ocess leads to the formation of sintered materials al a lower temperat ure compared to the undoped 2212 compound. The final composition is di scussed as a function of which crystallographic site is partially subs tituted. The presence of alkali ions in the initial chemical compositi on leads to improved electrical properties. Such data are correlated w ith the microstructure and chemical composition of the end-product.