Excellent multi-color emission and multi-mode optical ratiometric thermometer in (Ca, Tb, Eu, Sm)Nb2O6 phosphors based on wide O2–→Nb5+ CTB

To meet the demand of ultra-sensitive and high accurate temperature measurements especially in the fields of medical treatment and diagnosis, multi-mode FIR-based optical thermometers as a novel strategy have been developed in recent years. In this work, two types of temperature probes, CaNb2O6 (CNO): Tb3+, Eu3+ and CNO: Tb3+, Sm3+, are firstly designed by high-temperature solid-state method. CNO possesses bright cyan emission excited at 267 nm, wide band gap and good temperature sensing property relative to BaNb2O6 (BNO) and SrNb2O6 (SNO) materials due to sandwich-type structure. Upon 267 nm excitation, Tb3+–Eu3+/Sm3+ doped CNO phosphors achieve multi-color tuning by host → Tb3+→Eu3+/Sm3+ ET channels. Furthermore, the characteristic emission intensity of Tb3+ decrease quickly than that of Eu3+ and Sm3+ due to the competition between thermal quenching and ET process as temperature rising. In the view of different temperature-dependent behaviors, multi-mode FIR (FIR1: ITb1/IEu1/Sm1, FIR2: ITb2/IEu2/Sm2, FIR3: ITb1/IEu2/Sm2 and FIR4: ITb2/IEu1/Sm1) show excellent temperature-sensing performance with the maximum Sa and Sr of 0.036 K−1/ 4.09 % K−1 at high temperature. This work provides a new luminescent material to gain excellent optical thermometer with low cost and high accuracy by multi-mode FIR collaboration.