The intergrowth of YTa7O19 in L-Ta2O5 with Er3+/Yb3+ enhancing pure green upconversion luminescence intensity by molten salt synthesis

By using the molten salt synthesis with B 2 O 3 flux and adjusting the doping concentration of Y 3+ , the intergrowth of the YTa 7 O 19 phase in L-Ta 2 O 5 is achieved. This structure enhances the pure green upconversion luminescence (UCL) intensity, which is because the YTa 7 O 19 phase isolates the distribution of Er 3+ /Yb 3+ in the 2D layer, localizing the energy transfer from Yb 3+ to Er 3+ and reducing the loss during the energy transfer process. By adjusting the concentration of Er 3+ /Yb 3+ and the holding temperature, the green UCL integral intensity of the optimal sample is 1.09 times that of β-NaYF 4 :Er 3+ /Yb 3+ . The intergrowth of the YTa 7 O 19 phase in L-Ta 2 O 5 is demonstrated by high-resolution transmission electron microscopy (HRTEM) and comparing bandgap values, and the structure and properties cannot be obtained by solid phase sintering. Using the luminescence intensity ratio (LIR) technology, the absolute temperature sensitivity (S A ) and relative temperature sensitivity (S R ) were 0.01359 K −1 and 0.01001 K −1 , respectively. The phosphor-converted 980 nm LEDs based on samples are fabricated, the CIE color coordinate can reach (0.20, 0.76), which exceeds NTSC standard. This indicates that this material can be used for temperature sensing and luminescence display applications.