RARE-EARTH IONIC RADIUS AS A PARAMETER DETERMINING THE PROPERTIES OF NI-SUBSTITUTED, FE-SUBSTITUTED, AND PR-SUBSTITUTED REBA(2)CU(3)O(7-Y) SUPERCONDUCTORS

Distinct and strong dependence of T-c and resistivity of REBa(2)(Cu(1- x)Me(x))(3)O-7-y systems (RE-Y,Nd,Eu,Gd,Ho,Tm Me=Ni,Fe) on the value o f RE(3+) ionic radius was found. As RE changes from Tm to Nd the value of \partial derivative T-c/partial derivative x\ increases by approxi mately 3 and 4 times for Me=Ni and Fe correspondingly. Taking into acc ount similar behavior of RE(1-x)Pr(x)Ba(2)Cu(3)O(7-y) systems, the val ue of RE(3+) ionic radius may be considered as a parameter determining the properties of REBa(2)Cu(3)O(7-y) systems with substitutions occup ying different crystallographic positions.