In Fig. 5, the effect of sintering temperature on Tconset and Tcoffset were shown. The Y123 had the highest critical temperature, Tconset =97 K. The increasing of sintering temperature had dropped the critical temperature of these superconductors. However the increasing of sintering showed the effect on critical temperature indirectly that decrease oxygen content of Y134, Y145 and Y156 but not for Y123 . The difference of Tconset and Tcoffset in each sample was decreases as c/a increases.