A theoretical framework is presented to quantitatively understand and design single ion thermometers relying on multiple thermally coupled excited states to widen the window for accurate thermal sensing. The concept is shown to be feasible using a Pr3+, Gd3+-coactivated YAl3(BO3)4 phosphor with Gd3+ as a Boltzmann-based single ion luminescent thermometer. UV upconversion emission from the 6PJ levels of Gd3+ is sensitized through two-step excitation of Pr3+ at 450 nm to the states of the 4f15d1 configuration, followed by energy transfer to Gd3+, which is practically feasible with the use of high-power blue LEDs. Analysis of the temperature dependent emission demonstrates how simple thermodynamic principles can be applied to circumvent the fundamental limitations in temperature precision of a conventional two-level single ion luminescent thermometer to finally make one thermometry system applicable to a wide range of temperatures while retaining high precision. This work paves the way for the targeted design of luminescent thermometers tailored towards applicational requirements for temperature accuracy within specific temperature ranges.
- Light Science & Applications
- , the Nederlandse Organisatie voor Wetenschappelijk Onderzoek, the EU-Horizon 2020 FET-Open project NanoTBTech