Designing Optical Thermometers Using Down/Upconversion Ca 14 Al 10 Zn 6 O 35 : Ti 4+ , Eu 3+ /Yb 3+ , Er 3+ Thermosensitive Phosphors.

Down/upconversion Ca 14 Al 10 Zn 6 O 35 inorganic phosphors codoped with Ti 4+ /Eu 3+ or Yb 3+ /Er 3+ were prepared. The crystal structure and downconversion luminescence properties of Ca 14 Al 10 Zn 6 O 35 :Ti 4+ , Eu 3+ phosphors were studied in detail. Ti 4+ and Eu 3+ occupied Al 3+ and Ca 2+ sites in the host lattice, respectively. Under the excitation of 273 nm, the emission peak in the 300-570 nm band originated from the 2 T 2 → O 2- transition of Ti 4+ . The f-f transition of Eu 3+ ions generated multiple peaks in the 570-800 nm range. The emission intensity of Ti 4+ and Eu 3+ ions can be used as a fluorescence intensity ratio (FIR) signal. Based on the FIR technology, the maximum relative sensitivity ( S r ) and the minimum temperature uncertainty (δ T ) reached 1.41% K -1 and 0.07 K, respectively. Meanwhile, the temperature-sensing behaviors were explored by the temperature-dependent upconversion spectra of Er 3+ - and Yb 3+ -codoped Ca 14 Al 10 Zn 6 O 35 phosphors. Based on the fluorescence intensity ratio of thermal coupling levels (Er 3+ : 2 H 11/2 / 4 S 3/2 ), the maximum S r and minimum δ T of upconversion phosphors reached 1.28% K -1 and 0.08 K in the temperature range of 293-473 K, respectively. Ca 14 Al 10 Zn 6 O 35 :Ti 4+ /Eu 3+ (Yb 3+ /Er 3+ ) phosphors realize temperature sensors with higher relative sensitivity, and it is a good candidate material for optical temperature measurement.