Stable Upconversion Luminescence Color in BiTa ₇ O ₁₉ :Er ³⁺ /Yb ³⁺ Phosphors

Er 3+ /Yb 3+ co‐doped BiTa 7 O 19 (BT7O), CaTa 4 O 11 (CTO), LiBi 4 Ta 3 O 14 (LBTO), GdTaO 4 (GTO) and Bi 7 Ta 3 O 18 (B7T3O) tantalate‐based phosphors are prepared. The upconversion luminescence (UCL) spectra are measured under 980 nm laser excitation, and the UCL color (green‐to‐red ratio [S gr ]) is calculated. The effects of excitation power density, Er 3+ /Yb 3+ co‐doped concentration, and temperature on S gr were studied. The above variables have the least impact on BT7O:Er 3+ /Yb 3+ , and BT7O:Er 3+ /Yb 3+ possesses a stable S gr . BT7O, CTO, LBTO and GTO all have a layered structure. Er 3+ /Yb 3+ exhibits a 2D distribution, and the Er 3+ /Yb 3+ distribution layer spacings are different. BT7O has the largest layer spacing of 10.02 Å, thus having the highest and most stable S gr . In B7T3O, Er 3+ /Yb 3+ is in a 3D distribution, thus having the lowest and most unstable S gr . This study explored the relationship between the lattice structure and S gr , providing new ideas for obtaining upconversion phosphors with high and stable S gr .