Cyan-emitting　inorganic　phosphors　capable　of　closing　the　“cyan　gap”　(480–520　nm)　are　essential　for　developing　human-centric,　full-visible-spectrum　phosphor-converted　white　light-emitting　diodes　(pc-wLEDs).　Traditionally,　these　materials　are　created　by　doping　activators　into　the　standard　crystallographic　sites　of　selected　hosts.　Here,　we　report　an　efficient,　broadband　cyan-emitting　phosphor　SiO2:Al3+,Eu2+　produced　by　engineering　interstitial　activators　Eu2+　into　the　channel　along　c-axis　of　α-quartz　lattice.　Under　365　nm　light　excitation,　the　compound　exhibits　a　broad　cyan　emission　band　spanning　from　390　to　675　nm,　with　a　full　width　of　half　maximum　of　114　nm　(4975　cm−1),　thus　effectively　covering　the　blue-cyan-green　region　of　visible　spectrum.　Additionally,　it　demonstrates　excellent　thermal　stability　with　a　high　emission　intensity　retention　of　73%　at　423　K.　By　encapsulating　the　mixture　of　the　cyan-emitting　SiO2:Al3+,Eu2+　and　a　commercial　orange-red　phosphor　on　an　ultraviolet　(λem　=　365　nm)　chip,　a　full-visible-spectrum　pc-wLED　is　successfully　fabricated,　showing　a　Commission　Internationale　de　L＇Eclairage　1931　chromaticity　coordinate　of　(0.342,　0.359)　and　a　high　color-rendering　index　of　89.　This　study　not　only　provides　a　promising　cyan　emitter　but　also　inspires　the　future　design　of　inorganic　phosphors.　©　2024　Elsevier　Ltd