  An extended study on PdS is carried out with the measurements of the
resistivity, Hall coefficient, Raman scattering, and X-ray diffraction at high
pressures up to 42.3 GPa. With increasing pressure, superconductivity is
observed accompanying with a structural phase transition at around 19.5 GPa.
The coexistence of semiconducting and metallic phases observed at normal state
is examined by the Raman scattering and X-ray diffraction between 19.5 and 29.5
GPa. After that, only the metallic normal state maintains with an almost
constant superconducting transition temperature. The similar evolution between
the superconducting transition temperature and carrier concentration with
pressure supports the phonon-mediated superconductivity in this material. These
results highlight the important role of pressure played in inducing
superconductivity from these narrow band-gap semiconductors.
