In this study, Sb2O3 (Sb2O5) and Ta2O5 are used as co-dopants with TeO2 to stabilize the delta phase of bismuth oxide (delta-Bi2O3). Some compositions with formula (1 x) BiO1.5-(x /4) Sb2Te2O9 and (1 - x) BiO1.5-(x/4) Ta2Te2O9 (x = 0.1, 0.2, 0.3, 0.6, and 0.9) have been synthesized by solid state reaction at 850 degrees C and characterized by powder X-ray diffraction. The Bi0.9Sb0.05Te0.05O1.575, Bi0.9Ta0.05Te0.05O1.575 and Bi0.8Ta0.1Te0.1O1.65 retain a cubic fluorite structure of delta-Bi2O3 phase. The electric properties were studied by impedance spectroscopy. All samples were evaluated by calculating conductivities and activation energies. Various impedance model including constant phase element and the Warburg impedances have been used to interpret the Nyquist representations of electrical analyses.