Optical thermometry through green and red upconversion emissions in Er3+/Yb3+/Li+:ZrO2 nanocrystals

Variations of fluorescence intensity ratio of green (generated from Er3+ 2H11/2 and 4S3/2 levels) and red (generated from the sublevels of Er3+ 4F9/2 level) upconversion emissions in Er3+/Yb3+/Li+:ZrO2 nanocrystals have been studied as a function of temperature under 976 nm laser diode excitation. In the temperature range of 323-673 K, the maximum sensitivities of about 0.0134 K− 1 and 0.0104 K− 1 are obtained by using green and red emission, respectively. Er3+/Yb3+/Li+:ZrO2 nanocrystals show potential application value in nanoscale thermal sensor.