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Title:Nature of the band gap and origin of conductivity in PbO2 revealed by theory and experiment
Authors:David O. Scanlon, Aoife B. Kehoe, Graeme W. Watson, Martin O. Jones, William I. F. David, David J. Payne, Russell G. Egdell, Peter P. Edwards and Aron Walsh, 2011
Abstract: Lead dioxide has been used for over a century in the lead-acid battery. Many fundamental questions concerning PbO2 remain unanswered, principally: (i) is the bulk material a metal or a semiconductor, and (ii) what is the source of the high levels of conductivity? We calculate the electronic structure and defect physics of PbO2, using a hybrid density functional, and show that it is an n-type semiconductor with a small indirect band gap of approximately 0.2  eV. The origin of electron carriers in the undoped material is found to be oxygen vacancies, which forms a donor state resonant in the conduction band. A dipole-forbidden band gap combined with a large carrier induced Moss-Burstein shift results in a large effective optical band gap. The model is supported by neutron diffraction, which reveals that the oxygen sublattice is only 98.4% occupied, thus confirming oxygen substoichiometry as the electron source.
ICHEC Project:Defect chemistry of Lead Dioxide: Metallic or semiconducting?
Publication:Phys. Rev. Lett. 107, 246402 (2011)
URL: http://prl.aps.org/abstract/PRL/v107/i24/e246402
Status: Published

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