Bifunctional Luminescent Thermometer-Manometer Based on Cr³⁺–Cr³⁺ Pair Emission

Pressure dependence of spectral positions of the 2 E → 4 A 2 and 4 T 2 → 4 A 2 bands of Cr 3+ ions, resulting from changes in Cr 3+ –O 2– covalency and variations in crystal field strength, respectively, is commonly utilized in luminescence manometry. However, as demonstrated in this paper, the luminescence of Cr 3+ –Cr 3+ pairs shows insensitivity to pressure changes, making this signal suitable as a luminescence reference. The significant difference in the thermal and pressure dependences of luminescence with Cr 3+ occupying different crystallographic positions in CaAl 12 O 19:Cr 3+ enables the development of a dual-function luminescence thermometer that operates in both ratiometric and lifetime-based readout modes. The presented first demonstration on utilization of Cr 3+ –Cr 3+ pairs luminescence for sensing applications may rekindle interest in Cr 3+ –Cr 3+ pairs for the development of optical sensors for physical quantities.