Investigation of a phosphor mixture of LiAl5O8: Cr3+ and LuPO4: Tb3+ as a dual-mode temperature sensor with high sensitivity

A mixture of Cr3+-doped phosphor (LiAl5O8: Cr3+) and Tb3+-doped phosphor (LuPO4: Tb3+), named as SAMIX, was successfully prepared by the traditional high-temperature solid-state method, and its luminescence properties for temperature sensing were investigated. Under a resonance excitation of 543.8 nm corresponding to the 7F5 → 5D4 transition of Tb3+, both the emissions of Cr3+ and Tb3+ were observed, and their temperature-dependent intensity exhibits opposite tendency. Consequently, the fluorescence intensity ratio technique for temperature sensing based on the luminescence of Tb3+ and Cr3+ yields an excellent performance with a maximum relative sensitivity of 3.68% K−1 at 300 K. In addition, the lifetime of Cr3+ at 714 nm is strongly affected by the temperature. When the temperature rises from 300 to 600 K, the lifetime of Cr3+ at 714 nm will decrease monotonically from 6.34 to 1.12 ms. The maximum value of relative sensitivity based on the lifetime of Cr3+ reaches 0.80% K−1 at 520 K. All these investigations indicate that the SAMIX phosphor is one of the promising candidate materials for a dual-mode high-sensitivity temperature sensor.