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

The structural and superconducting properties of ( samples have been studied by x-ray diffraction, resistivity, a.c. susceptibility and oxygen content measurements. The effect of increasing La concentration in is in lowering the carrier concentration and decreasing , which is attributed to hole filling by La. This suppression of has been compensated by appropriate hole doping with Ca in (, which shows that for a fixed La content increases dramatically as the Ca content increases. For instance, in the oxide (, the 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.