INFLUENCE OF HOLE FILLING BY LA AND HOLE DOPING BY CA ON THE SUPERCONDUCTIVITY OF ERBA2CU3O7-BETA

The structural and superconducting properties of (Er1-xCax)Ba2-yLayCu3 Oz samples have been studied by x-ray diffraction, resistivity, a.c. s usceptibility and oxygen content measurements. The effect of increasin g La concentration in Er(Ba2-yLay)Cu3Oz is in lowering the carrier con centration and decreasing T-c, which is attributed to hole filling by La. This suppression of T-c has been compensated by appropriate hole d oping with Ca in (Er1-xCax)Ba2-yLayCu3Oz, which shows that for a fixed La content T-c increases dramatically as the Ca content increases. Fo r instance, in the oxide (Er1-xCax)Ba1.6La0.4Cu3Oz, the T-c increases from 35 K (x = 0.0) to 82 K (x = 0.4, compensated oxide) as the hole f illing by La is completely balanced by hole doping form Ca.