Boosting the Temperature Detection Accuracy of Luminescent Ratiometric Thermometry via a Multifunction Fit Strategy

The influence of fit strategy on the temperature detection accuracy of luminescence ratiometric thermometry is investigated here. In the range of 303-783 K, the typical ²H_11/2/⁴S_3/2-⁴I_15/2 upconversion emission lines of Er³⁺ embedded in calcium tungstate are investigated as a function of temperature. It is found that using the conventional one-function fit method over the whole temperature range leads to a mean error of 3.47 K. By contrast, the strategy, namely, dividing the whole board temperature range into several narrow ones and using several fit functions over separate temperature scopes, is proposed and studied. It is demonstrated that as the number of the divided temperature scopes is increased, the measured temperature readout gradually approaches to the true value of the temperature. When the number is set to be six, the temperature error sharply goes down to 0.41 K, suggesting that the newly proposed multi-function fit strategy is superior to the traditional one-function fit method, especially when a board temperature scope is involved. The reason responsible for this phenomenon is also discussed.