TL phosphor based on Ba1−x CaxSO4:Eu (1 at %) (0 < x < 1) was prepared using the chemical co-precipitation technique. XRD shows orthorhombic structure. It was found that the TL sensitivity of the material changes on varying the concentration of Ca and maximum sensitivity is found for Ba0.98Ca0.01SO4:Eu.01. Moreover, the phosphor had constant glow curve shape over a dose range of 100-1000Gy. The dose response is linear/sub-linear over the dose range 100-500 Gy, above which TL sensitivity saturates.