STRONG RARE-EARTH SIZE DEPENDENCE OF T-C IN RSR(2)CU(2.85)RE(0.15)O(Z)

We report a strong rare-earth size dependence of T-c in RSr(2)Cu(2.85) Re(0.15)O(z) (R=rare earth, z approximate to 7.2) compounds, unlike in RBa(2)Cu(3)O(y) compounds. A strong correlation is observed between t he superconducting transition temperature and the orthorhombicity of t he structure, which itself is R-size dependent. Orthorhombicity is hig hest for HoSr2Cu2.85Re0.15Oz and ErSr2Cu2.85Re0.15Oz compounds, which also have yielded the highest T-c(approximate to 7.2 K). Significantly , TbSr2CU2.85Re0.15Oz stabilizes in a 1-2-3 structure and also superco nducts(T-c approximate to 22 K), whereas EuSr2Cu2.85Re0.15Oz does not superconduct, although it forms a single phase.