Enhancement of Electrical Conductivity of Polycrystalline β-PbO by Exposure to Ozone Gas at Room Temperature

Polycrystalline β-PbO pellets were exposed to ozone gas at room temperature. They were oxidized rapidly up to the composition of PbO1.01 for 1 h. Then, a color change from bright yellow to greenish brown and an enhancement of electrical conductivity from 10-11 to 10-3 S cm-1 were observed. The pellets appeared to have been oxidized up to inside uniformly for 10 min by visual observation. Formation of secondary crystalline phases was not detected by X-ray powder diffraction. Differential thermal analysis showed a broad distinct exothermic peak locating at ∼520 K, which was ascribed to a release of the strain energy accumulated by the room-temperature oxidation. The temperature region corresponded to that of a decrease in conductivity, indicating that the carrier annihilation was closely related to the lattice relaxation. A tentative mechanism that atomic oxygen is a diffusing species with a high rate was proposed.