Controllable crystal form transformation and luminescence properties of up-conversion luminescent material K 3 Sc 0.5 Lu 0.5 F 6 : Er 3+ , Yb 3+ with cryolite structure.

In this paper, a novel cryolite-type up-conversion luminescent material K 3 Sc 0.5 Lu 0.5 F 6 : Er 3+ , Yb 3+ with controllable crystal form was synthesized by a high temperature solid state method. K 3 Sc 0.5 Lu 0.5 F 6 : Er 3+ , Yb 3+ can crystallize in monoclinic or cubic form at different temperatures. The composition, structure and up-conversion luminescence (UCL) properties of K 3 Sc 0.5 Lu 0.5 F 6 : Er 3+ , Yb 3+ samples with different crystal form were investigated in detail. It is impressive that both monoclinic and cubic forms of K 3 Sc 0.5 Lu 0.5 F 6 : Er 3+ , Yb 3+ show green emission ( 2 H 11/2 / 4 S 3/2 → 4 I 15/2 ). The luminescence intensity of cubic K 3 Sc 0.5 Lu 0.5 F 6 is much higher than that of the monoclinic form, and the reasons are also discussed in detail. The results show that the luminescence intensity of up-conversion materials can be effectively tuned by controlling the crystal form. According to the power dependent UCL intensity, the UCL mechanism and electronic transition process were discussed. In addition, the fluorescence decay curves were characterized and the thermal coupling levels (TCLs) of Er 3+ ( 2 H 11/2 / 4 S 3/2 → 4 I 15/2 ) in the range of 304-574 k were used to study the optical temperature sensing characteristics. All the results show that K 3 Sc 0.5 Lu 0.5 F 6 : Er 3+ , Yb 3+ can be used in electronic components and have potential application value in temperature sensing fields.