Interionic cross relaxation and tunable color luminescence in KY3F10:Tb3+ nano/microcrystals synthesized by hydrothermal approach

Color tunable phosphors of KY3(1−x)Tb3xF10 (KY3F10:xTb3+) were synthesized by the hydrothermal (HT) approach. The luminescence consists of a group of blue and green emission lines originating from 5D3→7FJ and 5D4→7FJ transitions of Tb3+, respectively. The emitting color tunes from blue to green by gradually increasing Tb3+ concentrations, which is attributed to the enhanced 5D3–5D4 cross-relaxation (CR) between two Tb3+ ions, as described by (5D3, 7F6)–(5D4, 7F0). The CR process is analyzed based on Inokuti–Hirayama model and ascribed to the electric dipole–dipole interaction. The energy transfer critical distance and critical concentration between Tb3+ ions are evaluated to be 8.03 Å and 4.61 × 1020 cm−3, respectively. Moreover, the initial transfer rate on acceptor concentration is also presented with an averaged CR coefficient.