Efficient energy transfer, multi-colour emitting and temperature sensing behavior of single-phase Tb3+, Eu3+ co-doped strontium fluoride phosphors

A succession of single-phase SrF2: Tb3+, Eu3+ phosphors with adjustable output colour were prepared via chemical co-precipitation technique. The crystal structure, scanning electron microscopy (SEM), photo-luminescence excitation (PLE) spectrum, photo-luminescence emission (PL) spectrum, photo-luminescence decay curve and thermal stability studies were used to analyze systematically the energy transfer (ET) properties in SrF2 host. SrF2:Eu3+ phosphors present an obvious orange fluorescence and SrF2:Tb3+ phosphors exhibit the characteristic green fluorescence. The optimal single dopant contents of Eu3+ and Tb3+ are 7 mol% and 6 mol%, respectively. By optical analysis, it can be inferred that Eu3+ and Tb3+ may mainly occupy the reverse symmetric position. Moreover, in the 6 mol% Tb3+, zmol% Eu3+ co-doped SrF2 samples, the intensity of terbium ions characteristic emission (545 nm) decreases monotonically and europium ions characteristic emission (592 nm) increases monotonously by elevating amounts of Eu3+ contents. Thus the alteration of light output colour from green to yellow and definitively to orange can be observed via appropriately adjusting Eu3+/Tb3+ ratios. ET type was testified in SrF2 host is a quadrupole-quadrupole mechanism. Additionally, the critical distance of ET from terbium to europium, which was calculated by quenching concentration method, was 10.521 angstrom. Meanwhile, the SrF2: 6 mol% Tb3+, 1 mol% Eu3+ exhibits a good thermal stability, so, it will have potential applications for n-UV w-LEDs.