An upconversion luminescence and temperature sensor based on Yb 3+ /Er 3+ co-doped GdSr 2 AlO 5 .

GdSr 2 AlO 5 :Yb 3+ /Er 3+ micro-particles were synthesized by a simple solid state method. The structure, morphology, size and upconversion luminescence features have been characterized. These results indicated that GdSr 2 AlO 5 has a contracted tetragonal cell and has irregular block shaped particles with sizes of about 5 μm. During upconversion, green ( 2 H 11/2 , 4 S 3/2 → 4 I 15/2 ) (527 nm, 549 nm) and red ( 4 F 9/2 → 4 I 15/2 ) (665 nm) emissions had been observed, both of which occurred via a two-photon population process. In addition, green UC emission characteristics were studied, and it was found that its temperature ranged from 293 K to 473 K and the sensitivity was 0.0054 K -1 at 473 K. This indicated that GdSr 2 AlO 5 :Yb 3+ /Er 3+ micro-particles may have potential application in high temperature environments for safety signs.