Preparation, characterization and investigation of (Tl1-xMx)Ba2Ca2Cu3O9-del
ta, where M = Zn and Ni with 0 less than or equal to x less than or equal t
o 0.6, are performed. Our results show that the transition temperature "T-c
" increases up to x = 0.2 for Zn substitution samples whereas it decreases
with increasing Ni content.