IN ORDER to investigate Sr-substitution effects on LaNiO3, LSN, …...properties, thermal analysis, x-ray diffraction, and scanning electron microscopy studies were used to characterize powder samples of La_1-xSr_xNiO₃, x= 0, 0.3, 0.5, 0.8 and 1, prepared by the sol-gel route via the polymerized complex method. Electrical conductivity and dielectric properties of the different compositions were also done. Samples of the complex solutions of molar ratios La (Sr)/Ni/citric acid (CA)/ethylene glycol (EG) = 1:1:10:40, were heated at 130°C to reach a gel form, dried at 350°C, crushed to the precursor powder LSN, then final calcination was performed at 800°C/2hr in air according to thermal analysis results. Elemental analysis through the EDS spectroscopy confirms the compositions. Ultrafine, nanoparticle samples having perovskite (ABO3) tetragonal crystalline were formed except that of x=1, SrNiO₃, which has a cubic one. The conduction mechanism changes from semi-conductive to metallic as Sr-incorporation increases and, σ seems to be temperature independent, while the dielectric values increase.