AbstractA novel deep‐red‐emitting phosphor Ca₂ScNbO₆:Mn⁴⁺ is prepared via a high‐temperature solid‐state reaction and its luminescent properties are systematically investigated. The results show that Mn⁴⁺‐activated Ca₂ScNbO₆ phosphors have broad absorption in ultraviolet region, and show bright deep‐red emission at 692 nm. The optimal doping concentration, crystal‐field strength, internal quantum efficiency, and mechanism of concentration and thermal quenching effects are discussed in detail. Moreover, NaF flux is screened out to improve both luminescent intensity and morphology of the phosphor. Finally, a red light‐emitting diode (LED) lamp is fabricated with as‐prepared Ca₂ScNbO₆:Mn⁴⁺ phosphors and a 365 nm LED chip. The electroluminescence spectra show a good overlapping with phytochrome P_R and P_FR absorbance. The results provided the as‐synthesized Ca₂ScNbO₆:Mn⁴⁺ phosphors a great potential in plant growth lighting.