Molten salt-synthesized Er3+/Yb3+/Sr2+-doped L-Ta2O5 with an intercalated intergrowth structure to boost the pure green upconversion luminescence

Er3+/Yb3+/Sr2+-doped L-Ta2O5 upconversion phosphors were synthesized using the molten salt method with B2O3 as the solvent. High-resolution transmission electron microscopy (HRTEM) results showed that Er3+/Yb3+/Sr2+ underwent intercalated intergrowth in L-Ta2O5. This structure facilitates energy transfer from Yb3+ to Er3+, resulting in outstanding pure green upconversion luminescence (UCL) intensity. The green UCL integrated intensity of L-Ta2O5:Er3+/Yb3+/Sr2+ was 1.53 and 3.14 times greater than that of β-NaYF4:Er3+/Yb3+ and the optimal NaY(WO4)2:Er3+/Yb3+ samples, respectively. The absolute and relative temperature sensitivity reached 1.383% and 0.992% K−1, respectively. The shift rate of the peak centroids reached 0.273 nm GPa−1 under high pressure. With its excellent performance, L-Ta2O5:Er3+/Yb3+/Sr2+ can be used in the fields of UCL display, temperature and pressure sensing.