Photoluminescence and thermoluminescence in Dy 3+ -, Ce 3+ -, and Tb 3+ -activated MgB 4 O 7 phosphor for dosimetry application.

Samples of microcrystalline rare earth-doped magnesium borate materials were synthesized via modified solid-state diffusion and were characterized using X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques. Photoluminescence (PL) results for the MgB 4 O 7 :Dy sample depicts blue emission that resulted from a 4 F 9/2 - 6 H 15/2 transition that peaked at 484 nm, which was much stronger than the yellow emission arising due to the 4 F 9/2 - 6 H 13/2 transition at 576 nm. From the emission spectra for MgB 4 O 7 :Tb, it seems that at higher concentrations of Tb 3+ ion, the green emission becomes strong and directly relates to the energy transfer from the 5 D 3 excited state to the 5 D 4 excited state through a cross-relaxation, whereas the blue emission is suppressed in MgB 4 O 7 phosphors. The thermoluminescence (TL) of the samples was measured immediately after irradiation and compared by TL curve with CaSO 4 :Dy. MgB 4 O 7 :Dy showed very good TL sensitivity for the desirable dosimetric curve at ~218°C and the best glow curve structure. In comparison with the dosimetric peaks for MgB 4 O 7 :Ce and MgB 4 O 7 :Tb, the MgB 4 O 7 :Dy phosphor is equally sensitive to CaSO 4 :Dy. MgB 4 O 7 :Dy and MgB 4 O 7 :Tb showed linearity for a 1-5 kGy dose. The activation energies and frequency factors were also calculated for samples MgB 4 O 7 :RE (where RE = Dy, Tb, Ce) using the peak shape method.