EPR and optical investigations of Eu 2+-doped BaFCl phosphor

Abstract

Europium-doped BaFCl phosphor has been prepared by solid-state reaction in carbon atmosphere. XRD measurements at room temperature confirm the presence of BaFCl phase in the sample. EPR, emission and excitation spectra have been studied. The EPR spectrum of the sample exhibits a well-resolved hyperfine structure of 151Eu 2+ and 153Eu 2+ isotopes. From the observed EPR spectra, g and A values have been evaluated. The EPR spectra have been studied at different temperatures. The number of spins participating in the resonance was calculated as a function of temperature and the activation energy was calculated. The paramagnetic susceptibility ( χ) was calculated at various temperatures from the EPR data and the Curie constant was calculated from the 1/ χ versus T graph. The emission spectrum of the sample exhibits a strong broadband centered at 386 nm. This band has been attributed to the 4f 65d 1(t 2g)→4f 7 transition. The excitation spectrum exhibits three bands centered at 216, 250 and 282 nm. The bands at 216 and 250 nm are attributed to oxygen-vacancy centers. The band at 282 nm is attributed to the 4f 7→4f 65d 1(e g) transition.