NON-ISOVALENT ALKALI-METAL SUBSTITUTION IN YBA2CU3O7-Y GRANULAR CERAMICS

The aim of this paper is to study the influence of non-isovalent ''dop ing'' in YBa2Cu3O7-y, in particular on its synthesis conditions and on the resistive properties both with and without a magnetic field. We c oncentrate on the study of possible alkali ions (Na, K, Cs) ''substitu tion'' at the barium sites. A low temperature sintering process is use d in order to induce a reactive liquid phase. The final chemical compo sition is discussed as a function of the amount of the liquid phase. N o alkali ion is substituted. Carbonate layers are present. However, th is (lack of) ''substitution'' leads to induced vacancies and improved electrical transport properties which are as good as in highly pure ma terials. For conciseness the case of Na ''substitution'' only is illus trated. The use of such data in order to probe the microstructure is e mphasized.