The La_0.8Sr_0.2Ga_0.8Mg_0.2O_3－α ceramics was synthesized via a sol-gel method. The structure and properties were determined and character-ized through XRD, DSC-TGA, SEM and AC impedance spectroscopy, gas concentration cell and gas elec-trochemical permeation (pumping) methods. The proton conduction behavior was studied by using electro-chemical methods for the first time. The compact ceramics had a good microstructure, and the relative den-sity was 95.1%. The experimental values of the hydrogen concentration cell coincided well with the theo-retical ones, and the ionic transport number was unity. It is a pure oxide ionic conductor in a dry oxygen at-mosphere. The observed rate of electrochemical hydrogen permeation was close to the theoretical rate, veri-fying that the ceramics was almost a pure proton conductor and the proton conductivity was 0.14 S•cm^－1 at 1000 ℃ under a hydrogen atmosphere.

Key words: LaGaO₃, sol-gel method, proton conductor, oxide ionic conductor, impedance