  The effects of planar hole concentration, p, on the resistivity, r(T), of
sintered Y1-xCaxBa2(Cu1-yZny)3O7-d samples were investigated over a wide range
of Ca, Zn, and oxygen contents. Zn was used to suppress superconductivity and
this enabled us to extract the characteristic pseudogap temperature, T*(p),
from r(T,p) data below Tco(p) [ = Tc (y = 0)]. We have also located the
characteristic temperature, Tscf, marking the onset of significant
superconducting fluctuations above Tc, from the analysis of r(T,H,p) and r(T,p)
data. This enabled us to identify T*(p) near the optimum doping level where the
values of T*(p) and Tscf(p) are very close and hard to distinguish. We again
found that T*(p) depends only on the hole concentration p, and not on the level
of disorder associated with Zn or Ca substitutions. We conclude that (i) T*(p)
(and therefore, the pseudogap) persists below Tco(p) on the overdoped side and
does not merge with the Tco(p) line and (ii) T*(p), and thus the pseudogap
energy, extrapolates to zero at the doping p = 0.19 +/- 0.01.
  PACS numbers: 74.25.Dw, 74.25. 74.62.Dh, 74.72.-h Key words: Pseudoap,
Superconducting fluctuations
