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Abstract: A novel series of ceramic samples (La0.97Sr0.03)2(Mo1−xGax)2O9−α (x=0, 0.01, 0.03, 0.05, 0.08) were prepared by a solid-state reaction method. All the doubly doped ceramics have a single cubic structure except (La0.97Sr0.03)2(Mo0.92Ga0.08)2O9−α. The conduction behaviors of the samples with x≤0.05 were investigated using various electrochemical methods including gas concentration cells, oxygen electrochemical permeation and AC impedance spectroscopy in the temperature range of 823–1273K. In dry oxygen-containing atmosphere, the ceramic samples were almost pure oxide-ionic conductors. In wet oxygen-containing atmosphere, the ceramic samples were also almost pure oxide-ionic conductors, but didn''t possess the protonic conduction. The electrochemical oxygen permeation experiment further verified the oxide-ionic conduction nature under oxygen-containing atmosphere. The phase transition has been completely suppressed in the doubly doped samples in both dry and wet air atmospheres. The oxide-ionic conductivities were affected by the doping levels, and increased in the order: σ (x=0.05)< σ (x=0)< σ (x=0.03)< σ (x=0.01). (La0.97Sr0.03)2(Mo0.99Ga0.01)2O9−α exhibited the highest oxide-ionic conductivity of 0.103Scm−1 at 1273K. [Copyright &y& Elsevier]

Abstract: Dense ceramic samples BaCe0.85−xZrxEr0.15O3-α (0.0≤x≤0.4) have been synthesized by heat-treating the precursor prepared through a microemulsion route. The obtained ceramic samples showed a single phase of orthorhombic perovskite. It was found that the ceramic powders of BaCe0.85−xZrxEr0.15O3-α were relatively stable when x≥0.2 after exposure in 94% N2 +3% CO2 +3% H2O atmosphere at 873.15K for 20h. The total conductivities of the ceramic samples decreased with increasing Zr content in the samples in wet hydrogen. Among the ceramic samples studied, BaCe0.65Zr0.2Er0.15O3-α displayed both a high chemical stability in 94% N2 +3% CO2 +3% H2O atmosphere and an acceptable conductivity at 573.15–1073.15K. The results indicated that BaCe0.65Zr0.2Er0.15O3-α was almost pure ionic conductor at 773.15–1073.15K in wet hydrogen atmosphere. The ionic conduction was contributed mainly by proton with transference numbers of 0.95–0.81 and partially by oxide ion with transference numbers of 0.02 to 0.08. In addition, BaCe0.65Zr0.2Er0.15O3-α was successfully applied to the ammonia synthesis at atmospheric pressure. The peak ammonia formation rate achieved 3.27×10−9 mols−1 cm−2 under a direct current of 1.0mA at 723.15K. [Copyright &y& Elsevier]

Abstract: Composites of Li4Ti5O12–Ketjen Black (Li4Ti5O12–KB) and Li4Ti5O12–Ketjen Black–multi-walled carbon nanotubes (Li4Ti5O12–KB–MWCNTs) are prepared by a simple solution method. Their morphologies and structures are characterized by X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy, and thermogravimetric analysis. Their electrochemical properties are investigated by galvanostatic charge–discharge test. Li4Ti5O12 particles in Li4Ti5O12–KB and Li4Ti5O12–KB–MWCNT composite have a diameter of ca. 40–60nm. The discharge specific capacity is 157 (0.1C), 110 (20C) and 93 (30C) mAhg−1 for Li4Ti5O12–KB composite, and 157 (0.1C), 133 (20C) and 105 (30C) mAhg−1 for Li4Ti5O12–KB–MWCNT composite. After 100cycles at 5C, the discharge capacity retention of Li4Ti5O12–KB and Li4Ti5O12–KB–MWCNTs is 94% and 96%, respectively. Li4Ti5O12 shows asymmetric behavior between charge and discharge. The excellent high rate performance of Li4Ti5O12–KB and Li4Ti5O12–KB–MWCNT composites can be attributed to the reduction of Li4Ti5O12 particle size and the improvement of electronic conductivity due to the uniform distribution of Li4Ti5O12 particles within the carbon matrix conductive network. [Copyright &y& Elsevier]