Infrared-to-visible up-conversion emissions and thermometric applications of Er3+-doped Al2O3

Er3+- doped Al2O3 has been prepared by a sol - gel method, using aluminium isopropoxide [ Al( OC3H7) 3]- derived Al2O3 sols with addition of erbium nitrate [ Er( NO3) 3 center dot 5H(2)O]. The phase structure theta-( Al, Er) O-2(3) phase was obtained for the 0.1 mol.% Er3+- doped Al2O3 at the sintering temperature of 1273 K. The green and red up- conversion emissions centered at about 523, 545 and 660 nm, corresponding respectively to the H-2(11/2) S-4(3/2) ->. I-4(15/2) and F-4(9/2) ->. I-4(15/2) transitions of Er3+, were detected by a 978- nm semiconductor laser diode excitation. The temperature dependence of green up- conversion emissions was studied over a wide temperature range of 295 - 725 K, and reasonable agreement between the calculated temperatures obtained by the fluorescence intensity ratio theory and the measured temperature was obtained, which proved that Er3+- doped Al2O3 has a good potential for the development of high- temperature sensors. It has some advantages compared to glasses due to its higher thermal and mechanical resistance and allows measurements in a large temperature range.