All-inorganic　lead-free　luminescent　metal　halides　doped　with　main-group　ns(2)-electron　ions　have　attracted　considerable　interest　in　a　variety　of　optoelectronic　applications.　However,　they　normally　suffer　from　severe　thermal　quenching　of　photoluminescence　(PL)　due　to　aggravated　nonradiative　relaxation　at　high　temperatures.　Herein,　we　report　a　new　class　of　luminescent　materials　based　on　5s(2)-electron　Sb3+-doped　0D　Cs3GdCl6　microcrystals　(MCs),　which　exhibit　intense　yellowish　PL　at　540　nm　under　ultraviolet　(UV)　excitation,　in　parallel　with　a　broad　bandwidth　of　510　meV,　a　large　Stokes　shift　of　190　nm,　a　near-unity　PL　quantum　yield,　and　remarkable　resistance　against　thermal　quenching　(I-150　degrees　C　=　82.4%).　Mechanistic　investigation　unravels　that　the　broadband　emission　originates　from　the　spin-orbital　allowed　P-3(1)　-＞　S-1(0)　transition　of　Sb3+　which　experiences　a　dynamic　Jahn-Teller　distortion　in　the　excited　state.　These　properties　facilitate　Cs3GdCl6:Sb3+　MCs　as　an　efficient　yellowish　phosphor　for　near-UV-converted　white　light-emitting　diodes,　demonstrating　a　high　color-rendering　index　of　96.4　and　excellent　operational　stability.　This　work　provides　not　only　fundamental　insights　into　the　excited-state　dynamics　of　Sb3+　in　Cs3GdCl6　MCs,　but　also　a　new　way　for　the　exploration　of　novel　and　highly　emissive　rare-earth　halides　through　ns(2)-electron　ion　doping　towards　various　light-emitting　applications.