We have obtained O-17 nuclear magnetic resonance spectra of magnetical
ly aligned Hg0.5Tl0.5Ba2(Ca1-xSr(x))2Cu3O8+delta at 300 K. The princip
al components of the electric-field gradient and the Knight-shift tens
ors are obtained for all oxygen sites in this mercury-based triple Cu-
O layered superconductor. The results show that both the EFG and Knigh
t shift tensors of the inner CuO2 plane oxygens are considerably small
er than those of the outer CuO2 plane oxygens, indicating a smaller sp
in susceptibility and a reduced hole density in the inner CuO2 plane.