Abstract: Owing to their unique optical properties, long-wavelength-emitting rare-earth-activated phosphors have important applications in optoelectronic fields such as white light-emitting diodes (LEDs). In this study, Sm³⁺-activated β-CaTa₂O₆ orange-emitting phosphors (CTO∶xSm, x=0.01~0.06) are successfully synthesized by high-temperature solid-state reaction method. Under excitation at 405 nm, the most intense emission peak is located at 606 nm originating from the ⁴G_5/2→⁶H_7/2 transition of Sm³⁺. The phase structure and luminescent properties were systematically characterized by XRD, Rietveld refinement, SEM, fluorescence spectra and thermoluminescence spectroscopy. The obtained phosphors are found to be single phase. Sm³⁺ ions are supposed to occupy Ca²⁺ sites, which leads a slight lattice contraction. The optimal doping concentration of Sm³⁺ is 2% (mole fraction) and the concentration quenching mechanism should be attributed to dipole-dipole interaction. An anomalous anti-thermal quenching behavior is also observed in CTO∶0.02Sm, which should be associated with defects induced by charge imbalance. The emission intensity initially increases rapidly and then slightly decreases with temperature rising. It reaches 239% of the room-temperature intensity at 548 K. The CIE 1931 chromaticity coordinates are (0.586 0, 0.411 2). It also shows a high color purity of 99.34% and a photoluminescence quantum yield (PLQY) of 41.83%. It should be promising for white LEDs with high color rendering index.

Key words: Sm³⁺, β-CaTa₂O₆, orange-emitting phosphor, luminescence property, anti-thermal quenching