High-sensitive temperature sensing based on thermal-enhanced emission and non-thermally coupled energy levels of white upconversion luminescence system

Na3Y(VO4)2:Nd3+,Yb3+,Ho3+,Tm3+ phosphors present significantly improved sensitivity of optical temperature sensing based on thermal-enhanced upconversion luminescence and non-thermally coupled energy levels. Under 808 nm excitation, white upconversion luminescence is successfully achieved in Nd3+-sensitized system. In addition, the emissions intensities originated from 4G5/2→4I9/2 transition of Nd3+ and 3F2,3→3H6 transition of Tm3+ gradually increase with elevating temperature owning to the thermal population effects, as opposed to the blue (1G4→3H6 transition of Tm3+), green (5S2,5F4→5I8 transition of Ho3+) and red (5F5→5I8 transition of Ho3+) emissions intensities show continuous decreasing trend. The temperature sensing behaviors are investigated by employing multiple non-thermally coupled energy levels. Based on non-thermally coupled energy levels of 4G5/2 (Nd3+)/1G4 (Tm3+), the absolute and relative sensitivities are obtained to be 0.433 K-1 and 2.81 % K-1. These results demonstrate that the Na3Y(VO4)2:Nd3+,Yb3+,Ho3+,Tm3+ phosphors with superior optical thermometry performance and white luminescence within a relatively wide temperature range can achieve optical applications in many fields.