Ratiometric optical thermometer with high-sensitive temperature sensing based on tunable luminescence of Ce3+-Eu2+ in KSr4B3O9 phosphors

• A novel Ce 3+ /Eu 2+ co-doped KSr 4 B 3 O 9 phosphor was designed. • The energy transfer process from Ce 3+ to Eu 2+ were investigated and discussed. • Thermal quenching behavior and related mechanism were investigated in detail. • The phosphor has potential to be applied in temperature-sensitive applications. It is a challenge to develop a new type of non-contact temperature sensor and the related materials with the advantages of high detection sensitivity, spatial resolution, non-invasive and fast response. In this work, a moderate solid-state method was utilized to prepare a novel Ce 3+ /Eu 2+ co-doped KSr 4 B 3 O 9 phosphor for efficient dual-emission temperature-sensing application. According to the different activation energy and the energy transfer process from Ce 3+ to Eu 2+ , two non-overlapping emission bands with respectively distinctive temperature responses were realized. By using the significant difference in the fluorescence intensity ratio between Eu 2+ and Ce 3+ , a strong shift of the CIE coordinate from (0.3701, 0.4311) at 293 K to (0.2623, 0.2465) at 443 K could be read out. Meanwhile, the maximum absolute (S a ) and relative sensitivities (S r ) were fitted to be 0.0118 and 2.25 % K −1 with a large chromaticity shift from 293 to 443 K (ΔE = 0.1652). The configuration coordinate diagram in KSr 4 B 3 O 9 was adopted to explain the temperature quenching mechanism in detail. The outstanding temperature-sensing characteristic indicates that KSr 4 B 3 O 9 : 1.75 %Ce 3+ /1.75 %Eu 2+ phosphor has the potential to be applied in a thermometric probe.