A significant enhancement of zero resistance temperature [T-c(zero)] from 78 K for x = 0 to 92.5 K for x = 0.2 in the series (Hg0.5Pb0.5)(Sr2-xBax)(Ca0.7Y0.3)Cu2O7-delta compounds has been found. On the basis of the O K-edge X-ray-absorption near-edge structure (XANES) spectra for the series of (Hg0.5Pb0.5)(Sr2-xBax)(Ca0.7Y0.3)Cu2O7-delta samples with x = 0-0.5, the chemical substitution of Ba2+ for Sr2+ gives rise to a decrease in the O 2p hole concentration within the out-of-plane oxygen sites, while that within the in-plane CuO2 layers remains almost unchanged for 0 less than or equal to x less than or equal to 0.2. This indicates that the out-of-plane oxygen may play an important role in controlling the increase of T-c(zero) up to the maximum value of 92.5 K.