Cr3+-doped double-perovskites for near-infrared luminescent ratiometric thermometry

Abstract The accurate measurement of temperature is of great importance in many fields ranging from industrial manufacture to our daily life, which can be finely implemented via the fluorescent intensity ratio (FIR) thermometry on the basis of Boltzmann distribution. Especially, the near-infrared (NIR)-emitting levels 4T2/2E of Cr3+ ion have recently emerged as the promising thermally coupled levels (TCLs), taking advantage of their superior optical property with high tunability. Herein, the crystal field strength around Cr3+ ions in double-perovskite La2MgHfO6 have been elaborately modulated via varying the dopant concentration, which greatly affect the intensity ratio between the spin-forbidden 2E → 4A2 and spin-allowed 4T2 → 4A2 transitions. Thermal sensing behaviors based on the TCLs (4T2/2E) were evaluated and the relative sensitivity gradually grew with the increase of crystal field strength. Above results offer guiding insights into the sensitivity optimization of Cr3+-based FIR thermometers, while providing the possibility of highly accurate measurement of temperature.