Tuning the band gap of PbCrO4 through high-pressure: Evidence of wide-to-narrow semiconductor transitions

•Electronic and optical properties of PbCrO4 are studied under compression.•Band-gap collapses are observed and correlated with structural phase transitions.•PbCrO4 band-gap is reduced from 2.3 to 0.8eV in a 20GPa range.•PbCrO4 is an n-type semiconductor with donor levels associated to Frenkel defects.•A deep-to-shallow donor transformation at HP induces a large resistivity decrease. The electronic transport properties and optical properties of lead(II) chromate (PbCrO4) have been studied at high pressure by means of resistivity, Hall-effect, and optical-absorption measurements. Band-structure first-principle calculations have been also performed. We found that the low-pressure phase is a direct band-gap semiconductor (Eg=2.3eV) that shows a high resistivity. At 3.5GPa, associated to a structural phase transition, a band-gap collapse takes place, becoming Eg=1.8eV. At the same pressure the resistivity suddenly decreases due to an increase of the carrier concentration. In the HP phase, PbCrO4 behaves as an n-type semiconductor, with a donor level probably associated to the formation of oxygen vacancies. At 15GPa a second phase transition occurs to a phase with Eg=1.2eV. In this phase, the resistivity increases as pressure does probably due to the self-compensation of donor levels and the augmentation of the scattering of electrons with ionized impurities. In the three phases the band gap red shifts under compression. At 20GPa, Eg reaches a value of 0.8eV, behaving PbCrO4 as a narrow-gap semiconductor.