ABSTRACT Among the undoped metal sulfates, on sintering at high temperatures, only BaSO4 was found to exhibit TL glow peaks in the region of radiation dosimetric interest i.e. ∼200°C (peak I) and 250°C (peak II). The TL intensity of peak I is very weak in purified BaSO4 but increased 4 times on 500°C, 1 h sintering. The intensity of peak II and the peak II/I height ratio increased with sintering temperature between 500°C and 1000°C. NaCl flux enhances the TL sensitivity of BaSO4 unlike that of Na2SO4. TL response of BaSO4 is in general linear below 1 kGy but unlike other phosphors, the TL response in the high dose region (> 1 kGy) does not saturate but increases sublinearly with dose (1–15 kGy) as a result of slow creation of traps by radiolysis. XRD shows that BaSO4 made with NaCl flux corresponding to a single phase of orthorhombic Barite crystal. The oxygen interstitial ions, are envisioned to be the hole traps and the radicals/anion vacancies formed by thermal dissociation of ions constitute the electron traps for peaks I and II, respectively. During TL, in the absence of dopants, the electron–hole recombination energy is observed under relaxed anion exciton emission in the 380–410 nm region. The phosphor is reusable after irradiation and TL readout. High dose irradiations, however, causes sensitization of TL after 400°C, 1 h post-irradiation anneal but a 700°C, 1 h anneal reduced the TL sensitivity. The creation of TL traps causing peak I precede that of peak II and a trap conversion between them occurs during high-temperature sintering. The study thus reveals for the first time that the defects causing TL peaks I and II are both thermally induced. Further studies to extend the saturation dose limit are proposed.