Energy transfer and unusual decay behaviour of BaCa2Si3O9:Eu2+,Mn2+ phosphor

In this work the photoluminescence (PL) of BaCa2Si3O9:Eu2+, Mn2+ and the energy transfer (ET) between Eu2+ and Mn2+ were examined. A series of powder samples with various Mn2+ concentrations were prepared by high temperature solid state route. Phase purity was investigated using X-ray powder diffractometry. Emission and excitation spectra as well as diffuse reflectance spectra were recorded to elucidate the PL properties of co-doped BaCa2Si3O9:Eu2+, Mn2+. Furthermore, fluorescence lifetime measurements were performed. PL and lifetime measurements were carried out from 100 to 800 K and 100 to 500 K, respectively. Moreover, external quantum efficiencies were determined and colour points were calculated. It turned out that ET from Eu2+ to Mn2+ is of a resonant type and occurs via dipole-quadrupole interactions. Temperature dependent PL measurements indicate high temperature stability of emission intensity in BaCa2Si3O9:Eu2+, Mn2+. Finally, it was found that fluorescence lifetimes of Eu2+ BaCa2Si3O9 show an unusual increase with increasing temperature.