Multi-color luminescence and thermal stability of eulytite-type Ba3La(PO4)3:Ce3+,Mn2+ phosphors via gel-combustion

Eulytite-type Ba(3)La(1-)x(PO4)(3): xCe(3+) (x = 0-0.10) and Ba3-yLa0.97(PO4)(3):0.03Ce(3+), yMn(2+) (y = 0.05-0.30) phosphors were first synthesized via gel-combustion and subsequent calcination in an Ar/H-2 atmosphere at 1250 degrees C. Photoluminescence properties of the phosphors were thoroughly studied, including excitation, emission, emission color, thermal stability and the process of Ce3+/Mn2+ energy transfer. The Ba3La(PO4)(3): xCe(3+), yMn(2+) phosphor series simultaneously exhibited the near-ultraviolet emission of Ce3+ (similar to 370 nm, 4f(0)5d(1) -> 4f(1)5d(0) transition) and the orange-red emission of Mn2+ (similar to 591-605 nm, T-4(1) -> (6)A(1) transition) upon exciting the Ce3+ ions with similar to 276 nm UV light. Owing to Ce3+ -> Mn2+ energy transfer most probably occurring via dipole-dipole interaction, gradually enhanced Mn2+ while weakened Ce3+ emission was resulted at a higher Mn2+ content, with which the emission color can be adjusted from blue through reddish-purple and ultimately to orange red. The efficiency of the energy transfer was analyzed to reach its maximum of similar to 43.2% at y = 0.30. It was shown that the Ba(3)La(1)x(PO4)(3): xCe(3+) and Ba3-yLa0.97(PO4)(3): 0.03Ce(3+), yMn(2+) phosphor series both have favorable thermal stabilities, whose activation energy for thermal quenching of luminescence was calculated to be similar to 0.28 +/- 0.02 eV for Ce3+ in the former while similar to 0.22 +/- 0.01 eV for Ce3+ and similar to 0.21 +/- 0.01 eV for Mn2+ in the latter system. Increasing temperature did not alter the emission wavelength of Ce3+ but gradually blue-shifted that of Mn2+ from similar to 602 to 583 nm with increasing temperature from 25 to 200 degrees C. (C) 2019 Elsevier B.V. All rights reserved.