Structurally induced tuning of the relative sensitivity of LaScO3:Cr3+ luminescent thermometers by co-doping lanthanide ions

Ratiometric luminescence thermometry for remote temperature sensing has been constantly gaining an increasing popularity due to its simplicity with yet high precision. Transition metal ions still have an underestimated potential in that area as their luminescence properties can be tuned by targeted modification of the host compound. In this work, we demonstrate that concept in the phosphor LaScO3:Cr3+ by co-doping with various lanthanide ions that partially substitute the La3+ ions of the host. It is demonstrated that the incorporated lanthanide ions affect the bond lengths of the [CrO6]9- octahedra in the structure and thus, have a subtle impact on the local crystal field around the Cr3+ ions. The changes in the crystal field strength lead to a variation in the energy gap between the thermally coupled 2E(g) and 4T2(g) states of Cr3+, which affects the thermal quenching behavior of the related 3d3-3d3 luminescence. This has an immediate consequence for the potential future use of Cr3+ together with lanthanide ions in a ratiometric luminescence thermometry and allows to selectively tune the performance of this structurally sensitive ion.