Low temperature photo-luminescence properties of Bi3+ doped Ca3Ga4O9 phosphor

Phosphors of Ca3Ga4O9, Ca3Ga4O9: 1 mol%Bi3+ and Ca3Ga4O9: 6 mol%Bi3+ were synthesized using high temperature solid state reactions. To clarify the origin of the luminescence centers, the temperature dependence of the absorption (excitation) and emission bands have been collected across the temperature range from 78 to 298 K. The absorption and emission peaks differ from low to room temperature. Photoluminescence spectra indicate that Bi3+ ions can occupy different Ca2+ sites, which is confirmed by the fluorescence lifetime of two emission centers. Emission excited with 274 nm light has features which only appear at low temperature. The origin of the peak is assigned to thermal coupling of 3P0 and 3P1, which is important for understanding the mechanism of the luminescence from Bi ions. Overall, the data confirm that the structure of Ca3Ga4O9 is an ideal matrix for the adjustment of the emission centers, especially for the ions which are highly influenced by the crystal field and coordination environment which may include more than one dopant ion.