Abstract
ABSTRACT According to the spectra of stationary X-ray excited luminescence (XEL) of BaF2: Eu nanophosphors at 80 and 294 K, it was revealed that the thermal annealing of fine-grained nanoparticles (d = 35 nm) in the range of 400–1000°C, which is accompanied by an increase of their sizes in the range of 58–120 nm, does not result in effective changes of the charge state of Eu3 + → Eu2 + activator, in contrast to CaF2: Eu nanoparticles. The maximum light output of X-ray excited luminescence of BaF2: Eu nanophosphors in the 590 nm emission band of Eu3+ ion was observed at an annealing temperature of 600°C with the average size of nanoparticles 67 nm. The subsequent growth of annealing temperatures, especially in the range of 800–1000°C, causes decrease in the light output of X-ray excited luminescence due to the increase of defect concentration in the lattice as a result of sharp increase of nanoparticle sizes and their agglomeration. In BaF2: Eu nanoparticles of 58 nm size, according to the thermostimulated luminescence (TSL) spectrum, transformation of Eu3+ → Eu2+ under the influence of long-time X-ray irradiation was revealed for the peak of 151 K. Thus, X-ray excited luminescence spectra of BaF2: Eu nanophosphors are formed predominantly due to the emission of Eu3+ ions, while emission of Eu2+ ions is observed in the TSL spectra.
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