DISAPPEARANCE OF SUPERCONDUCTIVITY IN OVERDOPED LA1.15-XPR0.85SRXCUO4AND THE ORTHORHOMBIC-TETRAGONAL PHASE-BOUNDARY

A study of the structural and electronic phase diagram of Pr-doped La2 -xSrxCuO4 is presented in order to investigate whether there is an inf luence of the high-temperature tetragonal-to-orthorhombic phase transi tion on the disappearance of superconductivity in the overdoped region . We find that Pr doping shifts the structural phase boundary to highe r Sr concentrations, but that superconductivity occurs in the same Sr- concentration range as in ''pure'' La2-xSrxCuO4. Thus, the disappearan ce of superconductivity is not related to the high-temperature structu ral transition, but is determined predominantly by the hole concentrat ion in the CuO planes.