Crystal structure, luminescence properties, energy transfer, tunable occupation and thermal properties of a novel color-tunable phosphor NaBa 1-z Sr z B 9 O 15 :xCe 3+ ,yMn 2 .

A series of color-tunable NaBa1-zSrzB9O15:Ce3+,Mn2+ phosphors were synthesized by a high temperature solid state method. Luminescence property, energy transfer, thermal stability and cation substitution were investigated in detail. Due to energy transfer, NaBaB9O15:Ce3+,Mn2+ presents violet to green luminescence and manifest a broad excitation range from 200 to 350 nm. The energy transfer mechanism of Ce3+-Mn2+ is identified as a dipole-dipole interaction. NaBa1-zSrzB9O15:Ce3+,Mn2+ displays both Ce3+ violet and Mn2+ green and orange emissions under ultraviolet excitation. It is observed that Sr2+ partial substitution for Ba2+ could adjust the ratio of Mn2+ emission intensity in different cation sites, which results from preferred sites' occupation with modification of the crystal structure. Furthermore, increase in temperature can enhance the energy transfer from Ce3+ to Mn2+, which enhances the Mn2+ emission intensity sharply. The highly thermal-sensitive property of NaBa1-zSrzB9O15:Ce3+,Mn2+ makes it feasible for its potential application in luminescent ratiometric thermometers with wide temperature range.