Electron traps based upon regular Pb sites perturbed by O vacancies (Vo) in high-purity undoped PbWO4 were revealed and studied by electron spin resonance and thermally stimulated luminescence measurements. Detailed analysis of electron spin resonance spectra parameters (g factor, hyperfine, and superhyperfine structures) along with the variation of the concentration after annealing in inert and O atmospheres had shown that revealed centers were Pb+-Vo complexes. The Pb+-Vo centers were created in two ways: (i) by direct trapping of the electrons from the conduction band under X-ray or ultraviolet irradiation at T = 60K; (ii) by re-trapping of electrons freed from unperturbed (WO4)3– centers after irradiation at T<40K, followed by heating at T = 60K. Above about 180K, Pb+-Vo centers were thermally ionized, giving rise to a TSL glow peak due to the recombination of freed electrons with localized holes. The emission spectrum of the thermally stimulated luminescence features one band peaking at around 2.5eV. The temperature dependence of both thermally stimulated luminescence and electron spin resonance intensities was analyzed by using a first order recombination model: the thermal ionization energy of Pb+-Vo centers turns out to be 0.55eV.

Photo-Induced Pb+ Center in PbWO4 - Electron Spin Resonance and Thermally Stimulated Luminescence Study. V.V.Laguta, M.Martini, A.Vedda, M.Nikl, E.Mihóková, P.Boháček, J.Rosa, A.Hofstätter, B.K.Meyer, Y.Usuki: Physical Review B, 2001, 64[16], 165102 (8pp)