Tuning Temperature Sensitivity by Chemical Composition in Cr 3+ -doped (Y 1– x Gd x ) 3 (Al 1– y Ga y ) 5 O 12

Remote temperature sensing using the temperature dependence of luminescence spectra or lifetimes of transition-metal and lanthanide ions is gaining popularity. For Cr 3+, the temperature dependence of lifetime of emission from the thermally coupled 2 E and 4 T 2 levels provides an easy and sensitive method to remotely measure temperature. The temperature range where the lifetime drops due to thermal population of the higher energy 4 T 2 level depends on the energy gap Δ E between the two levels. Here, we aim to vary Δ E for Cr 3+ -doped garnets (Y 1– x Gd x ) 3 Al 5 O 12 (0 ≤ x ≤ 0.8) and Y 3 (Al 1– y Ga y ) 5 O 12 (0.2 ≤ y ≤ 1) and show how tuning of Δ E by chemical composition can be used to optimize the temperature-sensing performance in a specific temperature range. The variation in Δ E can be understood by a decrease in crystal-field splitting resulting from a lengthening of the Cr 3+ –O 2– distance upon Al 3+ ↔ Ga 3+ or Y 3+ ↔ Gd 3+ substitution. Substitution of (Y,Gd) only gives a small variation of Δ E and shifts the temperature with the highest relative sensitivity S r by less than 50 K, while (Al,Ga) substitution allows for tuning the temperature with the highest S r from below 200 to around 300 K.