An international collaboration involving researchers from the University of Innsbruck has developed a novel luminescent material that enables particularly robust and precise optical temperature sensing across an exceptionally broad temperature range.

Optical luminescence thermometry has been gaining increasing attention, as it allows contactless temperature measurement even under extreme conditions. A key concept in this field is so-called ratiometric Boltzmann thermometry, in which the intensity ratio of two thermally coupled emission transitions directly follows the temperature. The performance of such thermometers crucially depends on the electronic structure of the luminescent ion and its incorporation into the host structure.

In a recent study, the two first authors, Gülsüm Kinik from the research group of Prof. Markus Suta at Heinrich Heine University Düsseldorf and Ingo Widmann from the research group of Prof. Hubert Huppertz at the Department of General, Inorganic and Theoretical Chemistry at the University of Innsbruck, reported the compound Al_0.993 Cr_0.007 B₄ O₆ N, which stands out as an exceptionally high-performance luminescence thermometer. The material is based on Cr³⁺ ions embedded in an almost ideal octahedral coordination environment, resulting in a particularly well-defined energy level scheme.