Influence of hole filling by La and hole doping by Ca on the superconductivity ofErBa2Cu3O7-δ

The structural and superconducting properties of (Er1-xCax)Ba2-yLayCu3Oz samples have been studied by x-ray diffraction, resistivity, a.c. susceptibility and oxygen content measurements. The effect of increasing La concentration in Er(Ba2-yLay)Cu3Oz is in lowering the carrier concentration and decreasing Tc, which is attributed to hole filling by La. This suppression of Tc has been compensated by appropriate hole doping with Ca in (Er1-xCax)Ba2-yLayCu3Oz, which shows that for a fixed La content Tc increases dramatically as the Ca content increases. For instance, in the oxide (Er1-xCax)Ba1.6La0.4Cu3Oz, the Tc increases from 35 K (x 0.0) to 82 K (x = 0.4, compensated oxide) as the hole filling by La is completely balanced by hole doping form Ca. (author)