Structural, thermal and optical investigations of PbF2:Eu3+ particles prepared by co-precipitation method

Sub-micro powder of Europium doped lead fluoride solid solution (Pb1-xEuXF2+x) is synthesized by co-precipitation method. The structural, thermal and optical properties have been studied. The DRX results for the as-grown samples show that an increase in Eu3+ concentration changes the PbF2 structure from a mixed phase to a cubic phase and a decrease of grain size. The DTA curve indicates that the α-PbF2 to β-PbF2 phase transition temperature is 357 °C. The sample structure is transformed from a pure alpha phase or mixed phases to a pure beta phase after annealing at 400 °C. The optical energy band gaps for Pb1-xEuxF2+x solid solutions have been determined. Excitation and emission properties have been discussed in details. The shorter wavelength emission lines are quenched by increasing the Eu3+ concentrations. This quenching effect is due to a cross-relaxation occurring between two neighboring Eu3+ ions. On another hand, the longer wavelength emission lines increase gradually up to 10% Eu3+ concentration and decrease at higher concentrations. The critical distance is determined to be 10 Å and the mechanism for concentration quenching has been elaborated.