The　interstitial　site　engineering　that　purposely　creates　interstitial　luminescent　centers　in　suitable　hosts　has　become　an　intriguing　strategy　in　designing　novel　inorganic　phosphors.　However,　effectively　tuning　the　photoluminescence　of　interstitial　activators　remains　tough　challenging　at　this　stage.　Here,　we　demonstrate　the　effective　modulation　of　interstitial　luminescence　in　inorganic　phosphor.　In　detail,　the　blue　emission　band　(λem　=　446　nm)　of　interstitial　Eu2+　doped　α-cristobalite　(SiO2:Eu2+)　is　largely　enhanced　and　broadened　via　a　partial,　aliovalent　substitution　of　Si4+　by　Al3+.　After　introducing　Al3+　ions　into　SiO2　lattice,　the　full　width　at　half　maximum　of　the　blue　emission　band　increase　from　59　to　76　nm　with　a　triple　growth　in　quantum　efficiency　(10.82%　→　35.56%).　Moreover,　the　thermal　stability　improves　significantly　with　a　high　emission　retention　of　60%　at　325　°C　(SiO2:0.06Al3+,0.005Eu2+),　far　higher　than　that　of　the　parent　SiO2:0.005Eu2+　(30%).　Encapsulating　blue-emitting　SiO2:Al3+,Eu2+　along　with　two　commercial　green　and　red　phosphors　on　an　ultraviolet　LED　chip　(λem　=　375　nm),　a　white　LED　device　with　high　color　rendering　index　(Ra　＞　90)　was　successful　fabricated,　showing　the　great　potential　of　this　phosphor　for　achieving　high-quality　white　LED　lighting.　This　study　not　only　provides　a　promising　bule　emitter　but　also　sheds　light　on　modulating　interstitial　luminescence　properties　in　inorganic　phosphors.　©　2025　Elsevier　Ltd　and　Techna　Group　S.r.l.