Mn4+-activated Sc-based hexafluoride red phosphor K5Sc3F14: Synthesis, luminescence, and its applications in blue-pump WLEDs

Due to the advantages of low phonon energy, structural diversity, excellent thermal stability and optical properties, fluoride compounds have sparked considerable research attention. On this foundation, a novel red-emitting phosphor, K₅Sc₃F₁₄:Mn⁴⁺ (abbreviated as KSF:Mn⁴⁺), was successfully designed and synthesized via a conventional co-precipitation process. The phosphor was comprehensively analyzed in terms of its phase, structure, morphology, elemental composition, and optical performance. Under blue light (473 nm) excitation, seven discernible emission peaks appear at 599, 609, 613, 622, 630, 634, and 647 nm, which can be attributed to the ²E_g to ⁴A_2g transition of the Mn⁴⁺ ions. Furthermore, the optimal molar ratio of K₅Sc₃F₁₄:K₂MnF₆ and crystal-field parameters (CFPs) are amply discussed. Ultimately, a warm WLED lamp with a high CRI (Ra = 87.5) and a low CCT (3289 K) was successfully created through the combination of a synthesized KSF:Mn⁴⁺ phosphor and a well-known YAG:Ce³⁺ phosphor, demonstrating that the developed phosphor is an appealing red component for high‐performance warm white illumination.