Non-stoichiometric BaFBr : Eu²⁺: a study on phase compositions and their relationship to F-centre formation

Even though image plate technology is successfully applied in x-ray detection, many questions concerning its detailed functional mechanisms have still not been answered. In this paper it will be shown that a previously suggested non-stoichiometric monophase of BaF 1.12 Br 0.88 : Eu 2+ resulting from the BaF 2 /NH 4 Br preparation route cannot be supported. It will be demonstrated by x-ray analysis that depending on the starting ratio of BaF 2 to NH 4 Br during sintering or the already synthesized BaFBr : Eu 2+ to BaF 2 during annealing, stoichiometric BaFBr : Eu 2+ with or without a BaF 2 phase will always be obtained. Furthermore, it will be shown that in the case of a molar stoichiometric starting ratio of BaF 2 /NH 4 Br, partial sublimation of NH 4 Br during sintering can be hold responsible for the appearance of BaF 2 as a second phase. Rietveld refinement is utilized to derive the quantitative amount of the individual phase compositions of BaFBr : Eu 2+ and BaF 2 . In terms of image plate properties, it will be shown that the composition of BaFBr : Eu 2+ and BaF 2 after the high temperature treatment determines the type of photostimulable colour centre generated during x-irradiation. Finally, the results obtained will be interpreted in terms of published photostimulated luminescence formation models.