Enhancement of Zero Resistance Temperature above 90 K and Hole Distribution in (Hg(0.5)Pb(0.5))Sr(2)(Ca(0.7)Y(0.3))Cu(2)O(7-delta) via Chemical Substitution of Ba into Sr Sites

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 (Hg(0.5)Pb(0.5))(Sr(2-x)Ba(x))(Ca(0.7)Y(0.3))Cu(2)O(7-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 (Hg(0.5)Pb(0.5))(Sr(2-x)Ba(x))(Ca(0.7)Y(0.3))Cu(2)O(7-delta) samples with x = 0-0.5, the chemical substitution of Ba(2+) for Sr(2+) gives rise to a decrease in the O 2p hole concentration within the out-of-plane oxygen sites, while that within the in-plane CuO(2) layers remains almost unchanged for 0