Influence of lanthanide (Gd, Tb or Ce) and silver doping on the luminescence lifetimes of calcium borate investigated by pulsed optically stimulated luminescence

Abstract

The objective of this work is to evaluate the optically stimulated luminescence (OSL) lifetimes of different polycrystalline CaB6O10:Ln, Agx (Ln = Gd, Tb and Ce; x: % molar concentration) compounds. For the determination of the luminescence lifetimes, time-tagged time-resolved (TTTR) data of the OSL under pulsed stimulation were analyzed. In addition, OSL emission spectra of the samples were recorded to correlate the emission bands with the estimated lifetimes. Whereas single Ce-doped compound presented a fast dominant component (τ < 0.41 μs, ∼63% of the signal), single Gd-doped compound exhibited a slow dominant component (τ = 2.3 ms, ∼67% of the signal). All Ag-codoped compounds (except for the Ce–Ag-codoped compound) presented a common dominant component with a ∼43 μs lifetime, which is ascribed to a broad emission centered at ∼330 nm. Both lifetimes and OSL emission spectra for the Gd-Ag-codoped compounds suggest that two luminescent centers compete for the radiative recombinations, confirming previous reported results. The relative Gd and Ag molar concentrations also had a strong influence in the estimated luminescence lifetimes of the slow component, probably due to the introduction of shallow trapping centers by silver doping. Furthermore, the temperature dependence of the common luminescence in Ag-codoped compounds appeared to be in agreement with the Mott-Seitz model for luminescence quenching. This work provides a better understanding of the physical processes and dynamics behind the radiative recombinations linked to OSL in borate compounds.