For thin membranes, the interface effect dominant the transport properties (i.e., r 0 !- < ,r 0 !- , , r 2, + < , and r 2, + , ), however, provided that the membrane is not thin, the interface effect can be neglected. In the current work, the samples were fabricated in order of hundreds of microns therefore the ASR of the mobile species (permeates) are only function of electrolyte electronic specific area resistance (r 2, + 9= , r 0 !- 9= r 9 9= ). Therefore, generally under load current (I X ) when on both sides of the membrane ∇µ 2, ≅ 0, the electrolyte is predominantly an O "# ionic conductor where GHK equation reduces to E <9== ?9,YZ:9C = φ 6 -φ 66 = E 0 ! -(I X . ASR 0 !-), which is consistence with only one species ionic conductor descriptions such as pure YSZ electrolyte in solid oxide fuel cell (SOFC) . When on both sides of the membrane ∇µ 0 ! ≅ 0, the electrolyte is a predominantly sodium-ion conductor, and E <9== ?9,YZ:9C = φ 6 -φ 66 = E 2, -(I X . ASR 2, + ) which is consistence with only one species ionic conductor descriptions such as pure NZGO electrolyte. Figure shows the measured open-circuit voltage (OCV) when the load current is zero (I X = 0) before and after equilibration. That is when the load resistance is infinite (here R X > potential and was compared to the corresponding calculated Nernst voltage (E 0 ! ). When the concentration of sodium at anode and cathode is zero, the GHK potential results in theoretical