Multichannel luminescence properties and ultrahigh-sensitive optical temperature sensing of mixed-valent Eu2+/Eu3+ co-activated Ca8ZrMg(PO4)6(SiO4) phosphors

A novel dual-emitting Ca8ZrMg(PO4)6(SiO4): (Eu3+, Eu2+) phosphors with ultrahigh-sensitive optical temperature sensing are prepared by a conventional solid-state method. The Eu2+/Eu3+ co-activated Ca8ZrMg(PO4)(6)(SiO4) phosphors exhibit efficient dual-mode emissions with an intense, broad blue emission peaked at 414 nm and a relative bright red-emitting centered at 614 nm under 297 nm UV-light excitation, respectively. Furthermore, the fluorescence intensity ratio (FIR) technology is applied to analyse the optical temperature sensing performance of Ca8ZrMg(PO4)(6) (SiO4): (Eu3+, Eu2+) phosphors. Based on different thermal quenching behavior of Eu2+ and Eu3+ dual-emitting centers, linear temperature-dependent FIR between Eu2+ and Eu3+ is obtained. The maximal absolute sensitivity reaches as high as 5.94% K-1, which is superior to that for the other luminescent temperature sensing materials reported previously. Analyses of the temperature-dependent photoluminescence spectra and configurational coordinate diagrams for Ca8ZrMg(PO4)(6) (SiO4): (Eu3+, Eu2+) phosphors indicate that the temperature-sensitive variation in FIR of Eu2+ to Eu3+ is originated from the difference in thermal quenching activation energy for 5d -> 4f transition of Eu2+ and D-5(0)-> F-7(J) (J = 1, 2, 4) transitions of Eu3+. These results reveal that the Ca8ZrMg(PO4)(6)(SiO4): (Eu3+, Eu2+) phosphors show glorious potential in high temperature optical thermometry. (C) 2019 Elsevier B.V. All rights reserved.