In this study, after doping Yb2O3 substance to alpha -Bi2O3 substance in the range of 1% a parts per thousand currency sign n a parts per thousand currency sign 8% in a series of different mole ratios, heat treatment was performed by applying a cascade temperature rise in the range of 700-790 A degrees C for 48 and 120 h and new phases were obtained in the (Bi2O3)(1 -aEuro parts per thousand x) (Yb2O3) (x) system. After 48 h of heat treatment at 750 A degrees C and 120 h of heat treatment at 790 A degrees C, mixtures containing 1-8% mole Yb2O3 formed a tetragonal phase. With the help of XRD, crystal systems and lattice parameters of the solid solutions were obtained and their characterization was carried out. Thermal measurements were made by using a simultaneous DTA/TG system. The total conductivity (sigma (T)) in the beta-Bi2O3 doped with Yb2O3 system was measured using four-probe d.c. method.