Neodymium doped lanthanum oxysulfide as optical temperature sensors

The fluorescence intensity ratio (FIR) technique for temperature sensing has been demonstrated in La2O2S:Nd3+ phosphors. The phosphors were extensively characterized using various methods such as X-ray diffraction, photoluminescence excitation, and photoluminescence spectra. Upon ultraviolet-visible (UV-vis) or near-infrared (NIR) light excitation, two intense NIR emissions of Nd3+ peaking at 897 nm and 1074 nm corresponding to transitions of 4F3/2→4I9/2 and 4F3/2→4I11/2 were generated at room temperature. NIR emission of Nd3+ in a wide temperature range from 30 K to 600 K was investigated. Experimental results show that the temperature evaluation can be realized by monitoring the emission peak position, measuring the fluorescence intensity ratio of 4F5/2 and 4F3/2 or that of the two Stark components of the 4F3/2 level in the bulk La2O2S:Nd3+. Furthermore, the effective energy difference of the thermalized levels 4F5/2 and 4F3/2, and 4F3/2 two Stark components were 987 cm−1 and 110 cm−1, respectively. Those results imply that La2O2S:Nd3+ phosphor is a potential candidate for the optical temperature sensor.