The thermal quenching effect of photoluminescent materials greatly limits their practical applications in bioimaging, sensing, radiation detection, and photovoltaic devices. In this paper, the upconversion luminescence (UCL) of Sc2W3O12:Er3+/Yb3+ was significantly improved by doping Ba2+ ions. The study identifies that the optimal doping concentration of Ba2+ ions within the negative thermal expansion (NTE) phosphors Sc2W3O12: Er3+/Yb3+ is 0.03 mol, the green and red light intensities of Sc2W3O12: Er3+/Yb3+/Ba2+ phosphor were increased by 32.76 times and 23.06 times. When the temperature rises from 298 K to 523 K, the NTE effect causes an abnormally increased luminous intensity. Utilizing fluorescence intensity ratio (FIR) technology, the temperature sensing characteristics of the Sc2W3O12: 0.30 Yb3+, 0.02 Er3+, 0.03 Ba2+ phosphor were further examined, achieving maximum relative and absolute sensitivities of 1.24 % K- 1 and 1.97 % K-1, respectively.