Optical high temperature sensor based on green up-conversion emissions in Er3+ doped Al2O3

Er3+ doped Al2O3 has been prepared by a non-aqueous sol–gel method using aluminum isopropoxide as precursor, acetylacetone as chelating agent, nitric acid as catalyzer, and hydrated erbium nitrate as a dopant in an isopropanol environment. The fluorescence intensity ratio (FIR) of the green up-conversion emissions at the wavelengths of about 523 and 545 nm in the Er3+ doped Al2O3 was studied as a function of temperature over a wide temperature range of 295–773 K, using a 978 nm semiconductor laser diode (LD) as an excitation source. The maximum sensitivity and the temperature resolution derived form the FIR of the green up-conversion emissions are approximately 0.0052 K−1 and 0.3 K, respectively. It is demonstrated that the prototype optical high temperature sensor based on the FIR technique from the green up-conversion emissions in the Er3+ doped Al2O3 is promising for applications in high temperature measurement.