Excitation and emission spectra and luminescence kinetics of Ca(AlxGa1 - x)2S4:Eu2+ crystals

Photoluminescence (PL) excitation and emission spectra of Ca(Al x Ga1–x )2S4:Eu2+ (х = 0.1, 0.2) crystals have been investigated at different temperatures (20–300 K) and europium concentrations (3, 5, 7%). The emission spectrum is a band peaking at 556 nm, which is due to 4f 65d → 4f 7(8 S 7/2) transitions in the Eu2+ ion. An increase in the Eu2+ concentration leads to an increase in the PL intensity by a factor of almost 3. Stokes shift ΔS = 0.32 eV, Huang–Rhys factor s = 10 ± 2, activation energy Е а = 0.02 and 0.03 eV, and lifetime τ = 250 ns are determined by analyzing the spectra.