The optical and steady-state photoconductivity spectra of 2 kinds of PbWO4 crystal, each grown in a different atmosphere, was reported. When the crystals were grown in air by Czochralski method, they exhibited a yellowish tint with additional spectral responses around 2.9 and 3.5eV as compared with the colorless crystals grown in Ar. Such additional features were attributed to a stoichiometric deficiency of Pb ions, resulting in the formation of two defect states of Pb3+ and O–.

Influence of Crystal Growth Atmosphere on the Formation of Color Centers in PbWO4 Single Crystals. T.H.Kim, S.Cho, K.Lee, M.S.Jang, J.H.Ro: Applied Physics Letters, 2002, 81[20], 3756-8