Structure, photoluminescence and thermal properties of Ce3+, Mn2+ co-doped phosphosilicate Sr7La3[(PO4)2.5(SiO4)3(BO4)0.5](BO2) emission-tunable phosphor

A single phase emission-tunable Ce3+, Mn2+ co-doped phosphosilicate Sr7La3[(PO4)(2.5)(SiO4)(3)(BO4)(0.5)](BO2) phosphor was synthesized by a solid-state reaction. Commonly blue and orange broad band emissions from Ce3+ and Mn2+ are detected under excitation at 351 nm. Combined with the crystallographic data from Rietveld refinements, the blue and orange bands can be fitted by the Gaussian function in accordance with the three different sites. By adjusting the ratio of Ce3+/Mn2+, warm-white light is generated with a correlated color temperature of 2500-4500 K. The mechanism of energy transfer between Ce3+ and Mn2+ has also been carefully investigated by the photoluminescence spectra and decay times. The thermal properties from 20 to 250 degrees C present an abnormal changing trend. With the increase in temperature, the Ce3+ or Mn2+ single-doped samples show excellent thermal properties, while for the Ce3+ and Mn2+ co-doped sample, the thermal properties are severely degenerated. Based on a configurational coordinate diagram, an underlying mechanism for thermal quenching is proposed which can reasonably explain the phenomenon. What is more, the mechanism could be helpful for understanding the thermal properties of phosphors co-doped with multiple activators as a reference.