Dual-emitting Eu2+/Eu3+ co-doped Ca9Zn1.5(PO4)7 phosphor for self-calibrated optical thermometry

Ca9Zn1.5(PO4)(7): Eu2+/Eu3+ phosphors had been synthesized via conventional high temperature solid-state reaction. Based on the different thermal quenching characteristics between 4f-5d transition of Eu2+ ions and 4f-4f transition of Eu3+ ions, the fluorescence intensity ratio (FIR) of Eu3+ to Eu2+ exhibits temperature dependence at the temperature from 293 to 473 K. The maximum absolute and relative temperature sensitivity of Ca9Zn1.5(PO4)(7): Eu phosphor can reach up to 0.0034 K-1 and 1.4% K-1 at 453 K, respectively, when used as thermometric material. These results indicated that our study opens up an effective approach for developing other high-performance self-calibrated optical thermometers.