Thermal history sensing from 1000 °C to 1400 °C based on phase transformation from Y3Al5O12 and Y4Al2O9 to YAlO3 through the intensity ratio method

Thermal history sensors are valuable tools for thermal analysis of high-temperature components within aero-engines and gas turbines. However, most thermal history sensors have an upper temperature limit of ∼1200 °C, which is insufficient to meet the requirement of gas turbines. This study introduces a novel material for thermal history sensing capable of measuring temperatures up to 1400 °C. We show thermal history measurements based on the emission intensity ratio of a Eu 3+ -doped yttrium–aluminum mixture, whose luminescence characteristics undergo irreversible changes when exposed to high temperature. The primary mechanism is the decrease of the symmetry ratio owing to the phase transformation from YAG (Y 3 Al 5 O 12 ), YAM (Y 4 Al 2 O 9 ) to YAP (YAlO 3 ) utilizing the combination reaction of YAP induced by heat-treatment. The intensity ratio between 5 D 0 → 7 F 1 and 5 D 0 → 7 F 2 exhibits a monotonic decrease from 1.3 to 0.4 as the heat-treatment temperature increases from 1000 °C to 1400 °C. Moreover, we demonstrate that the irreversible change in intensity ratio after heat treatment remains insensitive to exposure time and oxygen partial pressure. Thus, the Eu 3+ -doped yttrium-aluminum mixture is a promising material for manufacturing high-temperature thermal history sensors.