Reveal luminescence differences via comparative studies of dynamic spectra in Eu3+-activated BaLa2WO7 and SrLa2WO7 phosphors

Eu3+-doped BaLa2WO7 and SrLa2WO7 phosphors were prepared using the conventional solid-state reaction synthesis. The experiments have confirmed that the luminescence properties are completely different although they the isostructural monoclinic structure with a monoclinic space group of P21/b: compared with SrLa2WO7:Eu3+, BaLa2WO7:Eu3+ has stronger luminescence and higher thermal stability. The dynamic characteristics were studied via the laser site-selective excitation and luminescence technique. The two distinct Eu3+ centers Eu3+(A) and Eu3+(B) were confirmed corresponding to the substitution for La1 and La2, respectively. Eu3+(A) could transfer energy to Eu3+(B) in BaLa2WO7:Eu3+, but Eu3+(B) cannot realize back transfer to Eu3+(A). However, a mutual energy transfer could be achieved between Eu3+(A) and Eu3+(B) in SrLa2WO7:Eu3+ resulting in excitation energy diffusion. The energy dispersion may cause the excited electrons to be trapped in some defects and impurities, thereby reducing the luminescence effect. The results could help develop new reddish-orange emitting materials by introducing Eu3+ as a structural probe for doping sites and microstructure.