© 2022 Elsevier B.V.In this study, the effects of a triple doping strategy on the microstructure and electrical conductivity of Tb–Gd–Sm co–doped Bi2O3 systems were investigated. The XRD patterns generated after the conductivity measurements confirm that high–temperature conductivity tests (>700 °C) can help to stabilize the cubic δ–phase by creating a secondary annealing effect. At about 730 °C, the phase transition (α → δ) is noticeable on both the DTA curve and the conductivity plot of the sample 5Tb5Gd5Sm. The order–disorder transition is recognizable in samples 5Tb10Gd5Sm and 5Tb5Gd15Sm, resulting in two distinct conductivity regions. At 750 °C, the sample 10Tb5Gd5Sm has the highest conductivity of 0.0758 S/cm as well as the lowest activation energy of 0.27 eV.