Use of cross-relaxation for temperature sensing via a fluorescence intensity ratio

• Cross-relaxation between the 5D0-7F1 and 7F1-5D0 transitions of Eu3+ at D3 and C3v sites respectively dominates the temperature dependent fluorescence of the hexagonal YBO3:Eu phosphor.
• Rate of energy transfer between donor and acceptor ions is temperature dependent, making a fluorescence intensity ratio (FIR) of donor over acceptor emission indicator of temperature variation.
• A rough estimate using an expression 3/2kBT = ΔE gives an effective value of the low temperature limit of sensing range for FIR technique.

A scheme that provides an alternative mechanism for temperature sensing via a fluorescence intensity ratio (FIR) is proposed. The rate of energy transfer between rare-earth ions in a crystal or glass host is temperature dependent, and as such exhibits a changing intensity ratio in the emission spectrum. Here a phosphor YBO3:Eu3+ was used to illustrate the proposed sensing mechanism. The temperature dependence of the observed fluorescence is similar to the phenomenon found for the conventional FIR technique. The potential benefit of the proposed scheme is access to numerous additional varieties of active materials for FIR temperature sensing.