Ba²⁺ activated Ag₃PO₄ (APB6) orthophosphate as novel synthetic nanophosphor material were prepared using different impurity concentrations (1, 3, 5, 6 and 7 wt%) of BaCl2 salt. Coprecipitation method was used in preparation. The prepared nanophosphors were characterized via X-Ray Diffraction (XRD) and High-Resolution Transmission Electron Microscopy (HR-TEM) and the results confirmed the existence of nanoparticles. The thermoluminescence (TL) properties of the samples were extensively studied, where the APB6 sample with 6 wt% Ba2+ showed considerable TL characteristics. All the studied samples were subjected to optimum thermal annealing of 500oC for 1h and a heating rate of 5oC/s was applied. The TL response of APB6 nanophosphor exhibited the highest value in comparison with that of other compositions. In addition, APB6 sample revealed a good linearity of TL response within the gamma rat doses between 15 and 100 Gy, where a linear response is obtained with .0.9925 correlation coefficient. It also showed relationally low rate of fading of about 26% within a 50 days of storage. These good characteristics make the new prepared APB6 phosphor to be highly considered as a new potential TL dosimeter and can efficiently be used as γ-irradiation detector in many applications of ionizing radiation.