Yb/Er/Ho-α-SiAlON ceramics for high-temperature optical thermometry

Maximum operating temperature in optical thermometry is limited due to poor thermal stability of the sensing material at high temperatures. Here, Yb, Er and Ho-doped alpha-SiAlON (Yb/Er/Ho-alpha-SiAlON) ceramic prepared by hot press method has been studied for optical thermometry via upconversion under 980 nm excitation. The phase of the sintered ceramic has been confirmed by Rietveld refinement of the X-ray diffraction data. The temperature dependent upconversion was studied in a wide temperature range of 298-1023 K and fluorescence intensity ratio technique was used for temperature sensing behavior. Excellent spectral/thermal stability over the investigated temperature range was observed for the Yb/Er/Ho-alpha-SiAlON as the sensing material. The maximum values of absolute and relative sensitivity based on the thermally coupled levels of Er3+ are 59.2 x 10(-4) K-1 and 1.10 %. K-1 at 298 K and that based on non-thermally coupled levels are 108 x 10(-4) K-1 at 385 K and 0.345 %.K-1 at 329 K, respectively.