The present work aims at the investigation of the influence of different dopants' ionic radius and concentration on the lattice parameters and the density of Ce_1-xLn_xO_2-δ (x = 0-0.20; Ln = La, Nd, Sm, Eu, Gd, Dy, Ho, Er, Yb) solid solutions. Moreover, the temperature dependence of the linear expansion of Ce_0.8Ln_0.2O _2-δ ceramics is examined in the range of 300-1173 K and the respective thermal expansion coefficients are calculated. Finally, the total electrical conductivity of Ce_1-xLn_xO_2-δ (x = 0.15-0.20) and multi-component Ce_(1-x)Ln_x/2Ln' _x/2O_2-δ (x = 0.20; Ln = Sm, La, Gd, Dy and Ln' = Dy, Nd, Er, Y) systems is studied in a wide range of temperatures in air atmosphere, as well as in a wide range of oxygen partial pressures at 1023 K and 1173 K. According to the experimental results of the present work, at the highest examined temperature of 1173 K and in air atmosphere, the maximum values of total electrical conductivity are observed in the cases of Ce _0.8Nd_0.2O_2-δ and Ce_0.8Sm _0.2O_2-δ.