Achieving high thermal sensitivity from ratiometric CaGdAlO₄:Mn⁴⁺,Tb³⁺ thermometers

The pursuit of optical temperature sensing with high thermal sensitivity to discriminate small temperature changes without contact with the subject possesses a crucial technological and scientific significance. Ratiometric temperature detection based on transition metals and lanthanides emerges as a promising strategy to achieve the purpose due to the dopants' distinct thermal quenching rates. In this work, a new CaGdAlO₄:Mn⁴⁺,Tb³⁺ luminescent thermometer was developed. The combination of the highly-thermal-sensitive red emission from Mn⁴⁺ ions with the thermally-robust green emission from Tb³⁺ ions renders the thermometer with a maximum relative thermal sensitivity of 2.3% K^-1 at 398 K. The well-separated red and green channels in digital images enable further evaluation of thermal sensitivity. The estimated thermal sensitivity is 2.23% K^-1 at 398 K from the pixel intensity ratio of red and green channels.