  A wide-range doping was achieved by a high-pressure method for TbFeAsO1-x
from "under doped" to "over doped" superconducting compositions throughout the
optimized superconductivity (Tc of 44 K). Tc vs. lattice constant shows a
dome-shaped feature, while Tc vs. the lattice constant likely follows a unique
empirical curve over the doping range. The relatively large amount of oxygen
vacancies up to 0.3 per the formula unit was introduced possibly because of the
smaller replacement Tb than the other Ln (rare-earth element) in the LnFeAsO1-x
system.
