Multi-parametric thermal sensing based on NIR emission of Ho(III) doped CaWO 4 phosphors

Optical thermometry based on trivalent rare earth doped materials has attracted much attention recently. This article reported the temperature dependent near infrared luminescence of Ho 3+ doped in CaWO 4 phosphors. A series of CaWO 4 :Ho 3+ powders have been synthesized by high temperature solid state reaction. The XRD patterns showed that the Ho 3+ ions have occupied the lattice sites of Ca 2+ ions in the phosphors. The thermometry effect was demonstrated by different spectroscopic parameters through the emission intensity of Ho 3+ : 5 I 6 → 5 I 8 transition at ∼1190 nm, the spectral shift of the charge transfer band of W-O and the lifetime of Ho 3+ : 5 F 4 , 5 S 2 excited state. These three optical parameters present a simple linear relation with the temperature in the range of 30–300 °C. This allows for accurate thermal sensing based on simultaneous measurement of these parameters. Results show that CaWO 4 :Ho 3+ phosphors might be served as a potential candidate for thermometry.