Photostimulated luminescence and thermoluminescence in europium-doped barium magnesium fluoride

We present the results of thermoluminescence and photostimulated luminescence measurements of BaMgF4, a ferroelectric material which, when doped with divalent europium, can function as an efficient X-ray storage phosphor. While only a broad and largely structureless peak in the photostimulated luminescence excitation spectrum is observed, several trap centres are identifiable in thermoluminescence spectra. The broad peak in the photostimulated luminescence excitation spectrum is deduced to be an R centre and responsible for the observed storage phosphor effect. Madelung energy calculations of the fluorine site potentials in the BaMgF4 crystal structure were performed and indicate that three of the four distinct fluorine sites, F(2)–F(4), are energetically preferred for site vacancies, consistent with the assignment of the electron trap as an R centre.