Despite　possessing　admirable　features　for　optical　thermometry,　a　semiconductor　(SC)　nanocrystal　based　material　has　the　innate　shortcomings　of　poor　stability　towards　environmental　variation,　complicated/unfriendly　preparation　procedures,　low　production,　and　the　necessity　of　a　delicate　structural　design　to　achieve　dual-emission.　To　well　address　these　issues,　a　kind　of　dual-phase　devitrified　glass　(DG)　strategy　is　proposed.　In　the　case　of　dual-phase　DG　embedded　with　CsPbBr3　SC　and　EuPO4,　fabricated　via　a　glass　self-crystallization　route,　it　has　been　found　that　the　spatial　isolation　of　two　emitting　species　enables　non-interfering　luminescence　with　different　temperature-responsive　behaviors.　Utilizing　the　fluorescence　intensity　ratio　(FIR)　between　the　Eu3+:　4f　→　4f　emission　from　EuPO4　and　the　exciton　emission　from　CsPbBr3,　a　self-calibrating　thermometer　with　ultra-high　sensitivity　(Sa　=　0.082　K-1　and　Sr　=　1.80%　K-1,　303-483　K)　is　achieved.　Importantly,　the　introduction　of　a　CsPbBr3　perovskite　SC　into　the　inert　glass　matrix　greatly　improves　its　thermal　stability,　and　so　highly　repeatable　thermometry　in　the　dual-phase　DG　is　achieved　(97.12%　for　10　heating-cooling　cycles).　This　work　demonstrates　an　effective　pathway　for　accurate,　reliable　and　robust　thermometry　by　integrating　SC　nanocrystals　and　rare-earth-ions　into　an　inorganic　glassy　composite.　©　2018　The　Royal　Society　of　Chemistry.