Highly sensitive fluorescence intensity ratio thermometry by breaking the thermal correlation of two emission centers

Fluorescence intensity ratio thermometry based on hybrid Eu³⁺-doped GdVO₄ and Cr³⁺-doped Al₂O₃ particles has been studied. We aim at overcoming the limitation that the relative sensitivity (S_r) decreases with the square of temperature owing to the thermal relation between the two emitting levels in one matrix in terms of the Boltzmann distribution law. The design of hybrid Eu³⁺-doped GdVO₄ and Cr³⁺-doped Al₂O₃ particles constructs two emission bands with opposite temperature dependences. Furthermore, the S_r makes a breakthrough by obtaining greater sensitivity in a high-temperature range; the maximum value obtained is 1.4%K^-1 at 633 K.