A Newnew series of Yb3+/Er3+ ions co-doped Na3Gd (PO4)2 (NGPO) upconversion phosphors were synthesized by the solid-state method. The structural analyses indicate that all phosphors possess a single-phase monoclinic structure. Upon 980 nm excitation, the obtained compounds showed the featured green and red UC emissions of Er3+ ions. byBy controlling the laser pump power, the emission color is tunedturned from yellow to greenish-yellow. We have also investigated the UC emissions thermal properties between 300 and 440 K, using a dual-mode temperature sensor based on fluorescence intensity ratio of thermally coupled levels and non-thermally coupled levels. The maximum absolute and relative sensitivities are calculated to be 14.07 10-3 K-1 at 440 K and 1.45% K-1 at 300K respectively. Moreover, the heating effects produced by laser excitation was also measured. These results indicate that NGPO: Er3+/Yb3+ Phosphorsphosphors could be used for bifunctional applications in temperature sensing and optical heater devices.