A novel method for preparation of a dense diffusion barrier limiting current oxygen sensor is presented. The dense thin-layer with the nominal composition Sr-, Mg- and Fe-doped lanthanum gallate (LSGMF) was prepared over La0.8Sr0.2Ga0.8Mg0.2O3-delta (LSGM) electrolyte by a thermal diffusion method. The crystal structure, morphology, elemental distribution, conductivity, and sensing performance of the prepared sample were investigated. X-ray diffraction (XRD) analysis shows a highly crystalline perovskite. SEM-EDS analysis shows that the dense thin-layer with about 40 m thickness is well attached to the solid electrolyte. Electrical conductivity measurement shows that the dense thin-layer has high conductivity of 8.73 S.cm(-1) at 800 degrees C. The oxygen sensor exhibits good sensing performance. The variations of the limiting current (I-L) vs oxygen content (x(O-2)) can be obtained as follows: I-L(mA) = 96.65 x(O)(2) (mol) % vertical bar 28.62