Transmission measurements have been performed in reduced ${\mathrm{SrTiO}}_3$ between 300 and 17 K for different concentrations of oxygen vacancies. A midinfrared absorption band has been observed, whose behavior with doping and temperature is accounted for by an intraband scattering process, phonon or disorder assisted. Connections with the family of high-${\mathit{T}}_{\mathit{c}}$ superconducting oxides are demonstrated.

• Received 24 July 1992

DOI:https://doi.org/10.1103/PhysRevB.47.8917