Ratiometric and colorimetric fluorescence temperature sensing properties of trivalent europium or samarium doped self-activated vanadate dual emitting phosphors

Herein, a new optical thermometry scheme based on the differences in thermal quenching behavior between self-activated [VO4](3-) groups and rare earth doped ions is proposed by using fluorescence intensity ratio (FIR) technique. We successfully synthesized self-activated, Eu3+-, and Sm3+-activated singe-phase Ca2NaMg2V3O12 phosphors. The luminescence and temperature sensing properties of host, Ca2NaMg2V3O12:Eu3+ and Ca2NaMg2V3O12:Sm3+ were systematically investigated. By analyzing luminescence spectra, we find that Ca2NaMg2V3O12 exhibits a green broadband emission under 335 nm UV excitation, while Sm3+- and Eu3+-doped Ca2NaMg2V3O12 phosphors show one green broadband emission and some sharp lines, which originate from the CT between V5+ and O-2 of [VO4](3-) group and RE ions 4f-4f transition. Tunable color emission has been obtained by changing the contents of Eu3+ and Sm3+. With an increasing of the temperature, the fluorescence intensity of [VO4](3-) dramatically reduce while that of Eu3+ and Sm3+ slightly decline owing to the different quenching activation energy, which is 0.494 eV, 0.510 eV and 0.587 eV, respectively. Especially, Originated from the different thermal response, the FIR of Eu3+ and Sm3+ to [VO4](3-) show an amazing temperature sensing properties. The maximum relative sensitivity of Ca2NaMg2V3O12:Eu3+ and Ca2NaMg2V3O12:Sm3+ is 1.686% K-1 (443 K) and 1.889% K-1(463 K), respectively, which is much higher than most reported optical thermometry materials. The emitting color of Ca2NaMg2V3O12:Eu3+ was tune from green to reddish-orange in the range of 303 K-503 K while that of Ca2NaMg2V3O12:Sm3+ from green to orange. The experimental results indicated that the obtained phosphors may have potential applications in ratiometric and colorimetric temperature sensing.