Yanjie Xia

Electrical conductivity optimization in electrolyte-free fuel cells by single-component Ce0.8Sm0.2O2-δ–Li0.15Ni0.45Zn0.4 layer

Single-component electrolyte-free fuel cells possess a similar function to the traditional fuel cells with a complex three-component structure. However, how to enhance their electrical properties for practical industrial applications remains a timely and important issue. Here, we report the manipulation of concentration ratios of ionic to electronic conductors in an electrolyte-free Ce0.8Sm0.2O2-δ–Li0.15Ni0.45Zn0.4 by adjusting the relative weight between its two inside compositions. Our systematic investigations reveal that the fuel cell with 30% in weight of Li0.15Ni0.45Zn0.4 exhibits an almost uniform distribution of the two compositions and has a total conductivity as high as 10 × 10−2 S cm−1 at 600 °C. Such an enhancement is found to be attributed to the established balance between the numbers of its inside ionic and electronic conductors. These findings are relevant for the technological improvement of this new species of electrolyte-free fuel cell and represent an important step toward commercialization of this single-component fuel cell.

Identification of interfacial and bulk effects in modulating fatigue behaviors of Pb(Zr0.52Ti0.48)O3 thin films

The polarization fatigue behaviors of Pt/LaNiO3/Pb(Zr0.52Ti0.48)O-3/LaNiO3/Pt (Pt/LNO/PZT/LNO/Pt) and Pt/PZT/Pt structures under different temperatures T, voltages V-amp, and frequencies f are investigated in order to clarify defect-related interfacial and bulk effects. The fatigue endurance of the Pt/LNO/PZT/LNO/Pt structure is enhanced at higher T, larger V-amp, and lower f, whereas for the Pt/PZT/Pt structure a better antifatigue performance is obtained at lower T, smaller V-amp, and higher f. The defect chemistry as one of the origins of the switching fatigue is demonstrated by the predominant interfacial effect and bulk effect resulting in two types of markedly opposite fatigue responses. (c) 2007 American Institute of Physics.

Mechanism of A-B intersite charge transfer and negative thermal expansion in A-site-ordered perovskite LaCu3Fe4O12

Temperature induced intermetallic charge transfer and negative thermal expansion in compounds hold promise for many applications. Here, we report, by the first-principles calculations, the mechanism behind these effects and the associated electrical and magnetic properties of an A-site-ordered perovskite LaCu3Fe4O12. We find that the sensitive expansion of Cu-O bonds to temperature can trigger a transformation from Cu3+ to Cu2+, which imposes a covalent state transition of B-site Fe from +3 to +3.75. The resultant shrinkage of the Fe-O bonds is demonstrated to play a pivotal role in the volume contraction of the oxide at high temperatures.

B-site ordering induced suppression of magnetic cluster glass and dielectric anomaly in La2−xBixCoMnO6

We report the heat, magnetic, and dielectric properties of La2−xBixCoMnO6 with a series of Bi doping concentrations, focusing especially on the impact of A-site doping on B-site ordering. We demonstrate that the B-site ordering is enhanced via the Bi doping, resulting in a suppressed cluster-glass behavior, larger dielectric constant, and smaller tangent loss. Surprisingly, a pronounced step-like dielectric anomaly turns up near the spin-freezing temperature in the Bi-free oxide, which is suppressed significantly after Bi doping. We attribute the suppression of anomaly to the lessened amount of antisite defects at the B sites and the associated strengthened electronic localization.

First-Principle Investigation of Magnetic Coupling Mechanism in Hypothesized A-Site-Ordered Perovskite YMn3Sc4O12

We have systematically investigated the electronic and magnetic properties of hypothesized A‐site‐ordered perovskite YMn3Sc4O12 using first‐principle calculation based on the density functional theory. Our calculated results predict that YMn3Sc4O12 is both thermodynamically and mechanically stable and its ground state is antiferromagnetic insulator. The Mn3+ is in the high‐spin state. More importantly, by comparison to YMn3Al4O12, we point out that the empty Sc 3d orbital provides the MnOScOMn superexchange interaction, which is similar to its isostructural perovskite CaCu3Ti4O12, and enhances the antiferromagnetic interaction between Mn ions. From these calculations, we can clearly see that the empty 3d orbital plays an important role to realize superexchange interaction.