Infrared absorption spectra of doped and undoped lead azide

The far and near infrared absorption of thin films of pure and doped lead azide are reported. The effects of thallium and bismuth doping were investigated. The far ir lattice modes are essentially unaffected by doping; the near ir intra-azide ion modes are markedly affected by Tl doping. These effects are related to changes in the electronic properties with doping and are attributed to azide vacancies which compensate for, and pair with, substitutional Tl acceptors.