  The roles of aliovalent Ca(II)-for-Y(III) substitution and
high-pressure-oxygen annealing in the process of "superconducterizing" the
Co-based layered copper oxide, CoSr2(Y1-xCax)Cu2O7+d (Co-1212), were
investigated. The as-air-synthesized samples up to x = 0.4 were found
essentially oxygen stoichiometric (-0.03 <= d <= 0.00). These samples, however,
were not superconductive, suggesting that the holes created by the
divalent-for-trivalent cation substitution are trapped on Co in the charge
reservoir. Ultra-high-pressure heat treatment carried out at 5 GPa and 500C for
30 min in the presence of Ag2O2 as an excess oxygen source induced bulk
superconductivity in these samples. The highest Tc was obtained for the
high-oxygen-pressure treated x = 0.3 sample at ~40 K.
