Optical Temperature Sensor Capabilities of the Green Upconverted Luminescence of Er3+ in La3NbO7 Ceramic Powders

We present a study of the Er3+ upconverted luminescence in erbium doped Lanthanum Niobium Oxide, La3NbO7, ceramic powder, prepared by solid state reaction. This study focuses on the analysis of the feasibility of this system as a temperature sensor. Efficient UC luminescence was observed under the 975 nm excitation showing intense green, red and NIR (850 nm) emission bands. The NIR luminescence centred at about 850 nm and lying on the first biological window is mainly insensitive to the temperature. In contrast, the upconverted green bands, associated with the (H-2(11/2),S-4(3/2)) -> I-4(15/2) transitions, showed a high sensibility to temperature. Their temperature dependence was studied from RT up to 525 K, paying special attention to the physiological range of temperature (303-318 K). The high thermal sensitivities obtained, in comparison with other Er3+ and Er3+-Yb3+ based optical temperature sensors in such ranges, suggest the potential application of this phosphor in thermal sensing, suitable for both biological systems and other industrial applications requiring higher temperatures.