We have measured thermoelectric power (TEP) as a function of hole concentration per CuO2 layer Ppl in Y1−xCaxBa2Cu3O6 sPpl=x/2d with no oxygen in the Cu-O chain layer. The room-temperature TEP as a function of Ppl, S290sPpld, of Y1−xCaxBa2Cu3O6 behaves identically to that of La2−zSrzCuO4 sPpl=zd. We argue that S290sPpld represents a measure of the intrinsic equilibrium electronic states of doped holes and, therefore, can be used as a common scale for the carrier concentrations of layered cuprates. We shows that the Ppl determined by this new universal scale is consistent with both hole concentration microscopically determined by NQR and the hole concentration macroscopically determined by the formal valency of Cu. We find two characteristic scaling temperatures, TS * and TS2 * , in the TEP versus temperature curves that change systematically with doping. Based on the universal scale, we uncover a universal phase diagram in which almost all the experimentally determined pseudogap temperatures as a function of Ppl fall on two common curves; lower pseudogap temperature defined by the TS * versus Ppl curve and upper pseudogap temperature defined by the TS2 * versus Ppl curve. We find that while pseudogaps are intrinsic properties of doped holes of a single CuO2 layer for all high-Tc cuprates, Tc depends on the number of layers, therefore, the inter layer coupling, in each individual system.
