A ratiometric optical thermometer with multi-color emission and high sensitivity based on double perovskite LaMg0.402Nb0.598O3: Pr3+ thermochromic phosphors

Currently, non-contact fluorescence intensity ratio (FIR)-based luminescent thermometry has been extensively attracted great attention for its promising applications in electromagnetic field, micro-temperature field and thermally harsh environments. In this work, the double-perovskite LaMg0.402Nb0.598O3: Pr3+ (LMNO: Pr3+) thermometric phosphor is firstly designed and successfully synthesized via a high-temperature solid-state method. Under 450 nm excitation, the as-prepared samples simultaneously exhibit blue emission (3P0 → 3H4), green emission (3P1 → 3H4) and red emission (1D2 → 3H4, 3P0 → 3F2) of Pr3+. They present different dependence on the temperature due to the intervalence charge transfer state (IVCT). Accordingly, the four FIR models between 3P1 → 3H4 and 3P0 → 3H4 (G/B), 3P1 → 3H4 and 3P0 → 3F2 (G/R2), 1D2 → 3H4 and 3P0 → 3H4 (R1/B) and 1D2 → 3H4 and 3P0 → 3F2 (R1/R2) are used as temperature detecting signal in the range of 298–523 K, and the maximum absolute and relative sensitivity of LaMg0.402Nb0.598O3: 1.2% Pr3+ sample reached 0.0597 K−1 at 523 K and 0.7250% K−1 at 473 K, respectively. Excellent temperature sensing features are also demonstrated in the LaMg0.402Nb0.598O3: 0.3% Pr3+ and LaMg0.402Nb0.598O3: 2.0% Pr3+ samples. Except for high sensitivity for temperature sensing, the designed Pr3+-doped double-perovskite materials also realize the self-calibration by simultaneous monitoring of four models of FIR. Moreover, after five cycles, the relative luminescence intensity of LaMg0.402Nb0.598O3: 1.2% Pr3+ sample remains stable. These results indicate that LaMg0.402Nb0.598O3: Pr3+ phosphors have great promising application as self-calibrated optical temperature sensors.