CHEMICAL PRESSURE EFFECTS ON THE OPTIMIZATION OF T-C IN T' ELECTRON-DOPED SUPERCONDUCTING CUPRATES

We report a systematic variation of the superconducting properties wit h the Ln(3+) size and x in (Ln)(2-x)CexCuO4-delta T' compounds. Progre ssive higher T-C's with increasing interatomic Cu-O distances are foun d at the rate dT(CO)(d(Cu-O))approximate to 240 K Angstrom(-1) in x-op timized samples, having the same density of carriers in CuO2 layers. C harge transfer mechanisms have been isolated from all the rest modifyi ng T-C under pressure. The first can positively contribute to T-C in o verdoped samples, while the second are estimated to yield dT(CO)/dP ap proximate to-0.11 K/Kbar.