In this work, we present a study of two NaSICON families of general formula Na2.800M1.775Si0.900P2.100O12 with M=Zr or Hf. The synthesis was carried out using sol-gel process and the synthesized precursors were characterized using coupled DTA-TG. The obtained oxides after pyrolysis of precursors were identified by X-ray diffraction. The electric properties of the sintered oxides were carried out by impedance spectroscopy (SIC). The obtained results at this conditions highlight a good improvement of electrical conductivity (σ_tot around 10^-4S.cm^-1). This value is comparable to total electrical conductivity at 300K given in the literature.