Conduction mechanism and gas sensing properties of CoFe2O4 nanocomposite thick films for H2S gas

► Polycrystalline CoFe2O4 nanomaterials have been prepared by sol–gel citrate method for H2S gas detection. ► Conductivity was higher for 0.2wt% Sm and 10wt% Ni doped CoFe2O4. ► The sensor shows high degree of selectivity towards H2S gas at an operating temperature 200°C. Nanocrystalline 10wt% Ni and 0.2wt% Sm doped CoFe2O4 was prepared by sol–gel citrate method and calcined at different temperatures. The CoFe2O4 nanoparticles were characterized by X-ray diffraction (XRD), electrical properties were studied by impedance analysis. The XRD of CoFe2O4 shows cubic structure with grain growth of 40nm. The ac conductivity was studied for the sample 10wt% Ni and 0.2wt% Sm doped CoFe2O4 calcined at 650°C, at temperature range from 100 to 700°C over a wide range of frequencies from 50Hz to 200kHz. The result indicates that the ac conductivity depend on temperature, frequency and concentration of dopant. Nanocrystalline 10wt% Ni and 0.2wt% Sm doped CoFe2O4 was found to be good H2S sensor with high sensitivity and selectivity.