Polycrystalline semiconductor compounds of Cd0.8Zn0.2S and Sm3+ (0.01, 0.02, 0.03, 0.04 and 0.05 mol%) doped Cd0.8Zn0.2S samples have been synthesized by a controlled co-precipitation technique. The samples are characterized by X-ray diffraction (XRD). DC conductivity studies were performed in the temperature region 77-300 K by using a two probe method. The dc conductivity plots show the Arrhenius behavior with three different activation energies (Ea) in three different temperature regions (I (300-220 K), II (220-160 K), III (160-105 K), and they exhibited the variable range hopping conduction (VRH) mechanism at low temperature region (105-77 K). From the impedance, and dielectric measurements bulk resistance (R-g), capacitance (C-g), relaxation time (tau) and dielectric constant (epsilon) parameter values were calculated. And explained their variations with temperature and dopant (Sm3+) concentration changes. (C) 2015 Elsevier B.V. All rights reserved.