Nanocrystalline BaSO4 phosphors co-doped with 0.1 mol % Dy2O3 and various concentrations of Er2O3 (0.05–0.25 mol %) were synthesized by the co-precipitation method and investigated for low dose gamma dosimetry applications. The influence of Er3+ co-doping on the thermoluminescence response, trapping structure, and dosimetric performance of Dy doped BaSO4 phosphors was systematically investigated. Structural characterization using X-ray diffraction (XRD) and scanning electron microscopy (SEM) confirmed the formation of crystalline BaSO4 nanophosphors. Among the investigated compositions, the phosphor containing 0.15 mol % Er3+ exhibited the highest TL intensity and a prominent dosimetric glow peak at 399 K. The dosimetric properties of the optimized phosphor were evaluated. Under identical irradiation and readout conditions, the optimized phosphor exhibited a TL response approximately three times higher than that of the commercial LiF: Ti, Mg (TLD-100) dosimeter. Glow curve analysis using the Initial Rise (IR) and Computerized Glow Curve Deconvolution (CGCD) methods revealed the presence of seven trapping centers with activation energies ranging from 1.14 to 1.80 eV. Thermal fading behavior was investigated and was found to be mainly associated with the release of charge carriers from shallow trapping centers during the initial storage period. The minimum detectable dose was determined to be 9.39 mGy, and the phosphor exhibited good reproducibility and the TL response was linear within the dose range of 50 mGy to 10 Gy. These results demonstrate that Er3+ significantly influences the trapping structure and thermoluminescence performance of Dy doped BaSO4 phosphors. The optimized phosphor shows promising potential for low dose gamma radiation dosimetry applications.
