Multi-variable Bayesian optimization for a new composition with high Na+ conductivity in the Na3PS4 family

Na3PS4 is an archetypal room-temperature (RT), Na+-conducting, solid-state electrolyte. Various compositional modifications of this compound via iso/aliovalent substitution are known to provide a high ionic conductivity (ion) that is comparable...

F anion transport in nanocrystalline SmF3 and in mechanosynthesized, vacancy-rich Sm x—1BaxF3—x

Nanostructured materials can show considerably different properties as compared to their coarse-grained counterparts. Especially prepared by high-energy ball milling they are to be characterized by a large fraction of point defects in the bulk and structurally disordered interfacial regions. Here, we explored how the overall conductivity of SmF3 can be enhanced by mechanical treatment and to which degree aliovalent substitution is able to further enhance anion transport. For this purpose nanocrystalline (hexagonal) SmF3 was prepared by high-energy ball milling; mechanosynthesis helped us to replace Sm3+ in SmF3 by Ba2+ and to create vacancies in the F anion sublattice. We observed a remarkable increase in total (direct current) conductivity when going from nano-SmF3 to Sm1−x Ba x F3−x for x = 0.1. Electrical modulus spectroscopy was used to further characterize the corresponding increase in electrical relaxation frequencies.

Metal–Insulator Transition in Doped Barium Plumbates

Solid solutions in the Ba(Pb1−xSrx)O3−z system were prepared by aliovalent substitution of Pb4+ by Sr2+ ions to investigate the effect of cation stoichiometry on thermal and electrical properties as x was varied between 0 and 0.4, in the temperature range 300–523 K. The starting compound, barium plumbate (BaPbO3), has a perovskite structure and is known to exhibit metallic conductivity due to an overlap of the O2p nonbonding and the Pb–O spσ antibonding band, which is partially filled by the available electrons. The large difference in the ionic radii between the Pb4+ and Sr2+ ions introduces significant strain into the (Pb/Sr)O6 octahedra of the perovskite structure. Additionally, charged defects are created on account of the different oxidation states of the Pb4+ and Sr2+ ions. Evidence of a metal to insulator transition (MIT) of the Mott–Hubbard type has been observed at a critical concentration of Sr2+ ions.

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>