Tm3+/Yb3+ codoped CaGdAlO4 phosphors for wide-range optical temperature sensing

In this paper, single-phase CaGd1-x-yTmxYbyAlO4 (CGA:Tmx,Yby, 0.0005 ≤ x ≤0.005, 0.06 ≤ y ≤0.14) phosphors were synthesized by a combustion method in combination with a following heattreatment. It is found that their average grain sizes are in the range of ∼0.60–1.74 μm. For these phosphors under 980 nm excitation at room temperature, four sharp emission bands at 474, 651, 693 and 801 nm can be attributed to the 1G4→3H6, 1G4→3F4, 3F2,3 → 3H6 and 3H4→3H6 transitions of Tm3+ involving in the three-photon and two-photon processes. When x and y are equal to 0.001 and 0.10, respectively, the strongest UC emission intensity can be acquired. By employing the optimal phosphors, the wide-range temperature sensing from 173 to 823 K was realized based on LIR693/801 and FWHM801 parameters. The SA−LIR and SR−LIR in the temperature range from 300 to 823 K are in the range of 0.19–6.55 × 10−4 K−1 and 2.93–0.38 × 10−2 K−1, respectively. The SA−FWHM and SR−FWHM in the temperature range from 173 to 823 K are in the range of 4458-2044 × 10−4 K−1 and 0.20–0.05 × 10−2 K−1, respectively. Furthermore, our result demonstrates that CGA:Tm0.001,Yb0.1 phosphors has potential applications in wide-range optical temperature sensing working under extreme conditions.