A new series of Zr_1−xIn_xP₂O₇ (x=0.03, 0.06, 0.09, 0.12) samples were prepared by a solid state reaction method. XRD patterns indicated that the samples of x=0.03–0.09 exhibited a single cubic phase structure, and the doping limit of In³⁺ in ZrP₂O₇ was x=0.09. The conduction behavior was investigated in wet hydrogen using various electrochemical methods including AC impedance spectroscopy, isotope effect, gas concentration cells at intermediate temperatures (373–573 K). The conductivities were affected by the doping levels, and increased in the order: σ (x=0.03)<σ (x=0.12)<σ (x=0.06)<σ (x=0.09). The highest conductivity was observed for the sample Zr_0.91In_0.09P₂O₇ to be 1.59×10⁻² S·cm⁻¹ in wet hydrogen at 573 K. The isotope effect also confirmed the proton conduction of the sample under water vapor-containing atmosphere. It was found that in wet hydrogen atmosphere Zr_0.91In_0.09P₂O₇ was almost pure ionic conductor, the ionic conduction was contributed mainly to proton and partially to oxide ionic. The H₂/air fuel cell using x=0.09 sample as electrolyte (thickness: 1.73 mm) generated a maximum power density of 13.5 mW·cm⁻² at 423 K and 16.9 mW·cm⁻² at 448 K, respectively.

Dense ceramic samples BaCe_0.9−xZr_xSm_0.10O_3−α (x=0.10, 0.15, 0.20, 0.30) were obtained by heat-treating the precursors prepared from a coprecipitation route. The phase structure, chemical stability and conduction behaviors of the ceramic samples have been investigated by X-ray powder diffraction and alternating current impedance spectroscopy methods. All the ceramic samples displayed a single phase of orthorhombic perovskite. The samples with x≧0.20 were relatively stable after exposed to the flowing mixed gases: CO₂ +H₂O+N₂ at 873 K for 12 h. Among the samples tested, the sample with x=0.20 exhibited both adequate conductivity and better chemical stability. The contribution of different charged species for x=0.20 sample to the conduction in wet hydrogen atmosphere was investigated by means of gas concentration cells. It was found that the sample of x=0.20 was almost a pure ionic conductor, and the ionic conduction was contributed mainly by proton and partially by oxide ion in wet hydrogen atmosphere at 773–1073 K. The ammonia synthesis at atmospheric pressure in an electrolytic cell based on the sample of x=0.20 was successfully conducted and the peak ammonia formation rate achieved 2.67×10⁻⁹ mol·s⁻¹·cm⁻² with direct current of 0.80 mA at 773 K.

A series of La_0.90Ba_0.10Ga_1−xMg_xO_3−α (x=0.20, 0.25 and 0.30) ceramics with a perovskite-type orthorhombic structure were prepared by the conventional solid-state reaction. Their conduction was studied in wet hydrogen, wet air and dry air atmospheres by various electrochemical methods including AC impedance spectroscopy, isotope effect, electrochemical hydrogen pumping, steam concentration cells and oxygen concentration cells from 873 to1273 K. Proton conduction was confirmed directly by an electrochemical hydrogen-pumping experiment. The hydrogen evolution rates coincided with theoretical ones calculated from Faraday's law, indicating that in hydrogen atmosphere the charge carriers were predominantly protons. Isotope effect confirmed the ceramic samples possessed proton conduction under water vapor-containing atmosphere. In wet air atmosphere, the samples were found to be mixed (proton+oxide ion+hole) conductors, and in dry air atmosphere to be mixed (oxide ion+hole) conductors. These results were different from the reports that BaO- and MgO-doped LaGaO₃ ceramics were mixed conductors of oxide ion and electron hole in O₂ and air; whereas they were oxide ion conductors in N₂ and H₂ atmospheres.