Influence of Reduced Na Vacancy Concentrations in the Sodium Superionic Conductors Na11+xSn2P1−xMxS12 (M = Sn, Ge)

<p>Exploration of sulfidic sodium solid electrolytes and their design contributes to advances in solid state sodium batteries. Such design is guided by a better understanding of fast sodium transport, for instance in the herein studied Na₁₁Sn₂PS₁₂-type materials. By using Rietveld refinements against synchrotron X-ray diffraction and electrochemical impedance spectroscopy, the influence of aliovalent substitution onto the structure and transport in Na_11+<i>x</i>Sn₂P_1−<i>x</i><i>M_x</i>S₁₂ with <i>M</i> = Ge and Sn is investigated. Whereas Sn induces stronger structural changes than Ge, the found influence on the sodium sublattice and the ionic transport properties are comparable. Overall, a reduced in-grain activation energy of Na⁺ transport can be found with the reducing Na⁺ vacancy concentration. This work explores previously unreported phases in the Na₁₁Sn₂PS₁₂ structure type that, based on their determined properties reveal Na⁺ vacancy concentrations to be an important factor guiding further understanding within Na₁₁Sn₂PS₁₂-type materials.</p>

Influence of Reduced Na Vacancy Concentrations in the Sodium Superionic Conductors Na11+xSn2P1−xMxS12 (M = Sn, Ge)

<p>Exploration of sulfidic sodium solid electrolytes and their design contributes to advances in solid state sodium batteries. Such design is guided by a better understanding of fast sodium transport, for instance in the herein studied Na₁₁Sn₂PS₁₂-type materials. By using Rietveld refinements against synchrotron X-ray diffraction and electrochemical impedance spectroscopy, the influence of aliovalent substitution onto the structure and transport in Na_11+<i>x</i>Sn₂P_1−<i>x</i><i>M_x</i>S₁₂ with <i>M</i> = Ge and Sn is investigated. Whereas Sn induces stronger structural changes than Ge, the found influence on the sodium sublattice and the ionic transport properties are comparable. Overall, a reduced in-grain activation energy of Na⁺ transport can be found with the reducing Na⁺ vacancy concentration. This work explores previously unreported phases in the Na₁₁Sn₂PS₁₂ structure type that, based on their determined properties reveal Na⁺ vacancy concentrations to be an important factor guiding further understanding within Na₁₁Sn₂PS₁₂-type materials.</p>

Electrochemiluminescene detection of oxygen vacancies in layered double hydroxides

A novel electrochemiluminescence (ECL) platform was established to screen oxygen vacancies in layered double hydroxides (LDHs) by fabricating graphitic carbon nitride/LDH nanocomposites. The oxygen vacancy concentrations determined by the developed...

The Effects of Severe Plastic Deformation and/or Thermal Treatment on the Mechanical Properties of Biodegradable Mg-Alloys

In this study, five MgZnCa alloys with low alloy content and high biocorrosion resistance were investigated during thermomechanical processing. As documented by microhardness and tensile tests, high pressure torsion (HPT)-processing and subsequent heat treatments led to strength increases of up to 250%; as much as about 1/3 of this increase was due to the heat treatment. Microstructural analyses by electron microscopy revealed a significant density of precipitates, but estimates of the Orowan strength exhibited values much smaller than the strength increases observed. Calculations using Kirchner’s model of vacancy hardening, however, showed that vacancy concentrations of 10−⁵ could have accounted for the extensive hardening observed, at least when they formed vacancy agglomerates with sizes around 50–100 nm. While such an effect has been suggested for a selected Mg-alloy already in a previous paper of the authors, in this study the effect was substantiated by combined quantitative evaluations from differential scanning calorimetry and X-ray line profile analysis. Those exhibited vacancy concentrations of up to about 10−3 with a marked percentage being part of vacancy agglomerates, which has been confirmed by evaluations of defect specific activation migration enthalpies. The variations of Young’s modulus during HPT-processing and during the subsequent thermal treatments were small. Additionally, the corrosion rate did not markedly change compared to that of the homogenized state.

Regulation of different ratios of Sr doping and O vacancies on the magnetic properties of anatase TiO2

Theoretical calculations on the effects of different Sr-doped ratios and oxygen vacancy concentrations on the magnetic mechanism of anatase TiO2 are rarely reported. For this problem, generalized gradient approximation (GGA) plane wave ultra-soft pseudopotential [Formula: see text]U based on the spin density functional theory framework was adopted in this work. The effect of different Sr doping ratios and O vacancy concentrations on the magnetic properties of anatase TiO2 was studied by first principles. Results show that Sr replaces Ti and O vacancies at different Sr:V[Formula: see text] ratios (1:0, 1:1, 1:2, 2:1 and 2:2), the doping system is magnetic when the Sr:V[Formula: see text] ratio is 1:2. The systems with Sr[Formula: see text]:V[Formula: see text] ratios of 1:0 and 2:1 are nonmagnetic, whereas those with 1:1, 1:2, and 2:2 Sr[Formula: see text]:V[Formula: see text] ratios are magnetic. Regardless of whether or not Sr replaces Ti and O vacancies or interstitial Sr and O vacancies in different ratios of anatase TiO2, the effect of magnetic switching can be achieved by adjusting the concentration. In this study, the largest magnetic moment of Ti[Formula: see text]Sr[Formula: see text]O[Formula: see text] system is obtained at Sr[Formula: see text]:V[Formula: see text] ratio of 2:2. The Curie temperature of the doping system is above room-temperature, and the doping system produces 100% electron spin polarizability and is half-metallized. These features are valuable to the design and preparation of novel dilute magnetic semiconductors with spin-electron injection sources. The main magnetic sources of the Ti[Formula: see text]Sr[Formula: see text]O[Formula: see text] system are the holes generated by doped Sr and O vacancy complexes, which cause the spin polarization double exchange of Ti-3d electron orbitals and O-2p electron orbits near O vacancies. This result is consistent with the average field approximation and dual exchange mechanism theories.