A　series　of　Bi3+/Eu3+　co-doped　Ca2Ta2O7　(CTO:Bi3+/Eu3+)　phosphors　were　prepared　by　high-temperature　solid-state　method　for　dual-emission　center　optical　thermometers　and　white　light-emitting　diode　(WLED)　device.　By　modulating　the　doping　ratio　of　Bi3+/Eu3+　and　utilizing　the　energy　transfer　from　Bi3+　to　Eu3+,　the　tunable　color　emission　ranging　from　green　to　reddish-orange　was　realized.　The　designed　CTO:0.04Bi(3+)/Eu3+　optical　thermometers　exhibit　significant　thermochromism,　superior　stability,　and　repeatability,　with　maximum　sensitivities　of　S-a　=　0.055　K-1　(at　510　K)　and　S-r　=　1.298%　K-1　(at　480　K)　within　the　temperature　range　of　300-510　K,　owing　to　the　different　thermal　quenching　behaviors　between　Bi3+　and　Eu3+　ions.　These　features　indicate　the　potential　application　prospects　of　the　prepared　samples　in　visualized　thermometer　or　high-temperature　safety　marking.　Furthermore,　leveraging　the　excellent　zero-thermal-quenching　performance,　outstanding　acid/alkali　resistance,　and　color　stability　of　CTO:0.04Bi(3+)/0.16Eu(3+)　phosphor,　a　WLED　device　with　a　high　Ra　value　of　95.3　has　been　realized　through　its　combination　with　commercially　available　blue　and　green　phosphors,　thereby　demonstrating　the　potential　application　of　CTO:0.04Bi(3+)/0.16Eu(3+)　in　near-UV　pumped　WLED　devices.