Ionic conductivities of Ni/Al layered double hydroxides (Ni-Al LDHs) intercalated with CO32-, Cl- and OH- were evaluated in the temperature range of 25-80 degrees C under 65-95% relative humidity. X-ray diffraction and Fourier transform infrared measurements confirmed the formation of Ni-Al LDHs intercalated with CO32-, Cl- and OH-. In the AC conductivity measurements, Ni-Al LDH intercalated with CO32- (Ni-Al CO32- LDH) showed the highest ionic conductivity among them. The ionic conductivity of Ni-Al CO32- LDH was 1.3 x 10(-2) S cm(-1) at 80 degrees C under 80% relative humidity. The electromotive force for the water vapor concentration cell using Ni-Al CO32- LDH showed similar behavior with that using anion exchange membrane, indicating that Ni-Al CO32- LDH is a hydroxide ion conductor. Pelletized Ni-Al CO32- LDH was confirmed to work as the electrolyte of alkaline-type direct ethanol fuel cell. (C) 2012 Elsevier B.V. All rights reserved.