Oxide-ion conductors have found applications in various electrochemical devices, such as solid-oxide fuel cells, gas sensors, and separation membranes. Dion-Jacobson phases are known for their rich magnetic and electrical properties; however, there have been no reports on oxide-ion conduction in this family of materials. Here, for the first time to the best of our knowledge, we show the observation of fast oxygen anionic conducting behavior in CsBi 2-Ti 2 NbO 10−δ. The bulk ionic conductivity of this Dion-Jacobson phase is 8.9 × 10 −2 S cm −1 at 1073 K, a level that is higher than that of the conventional yttria-stabilized zirconia. The oxygen ion transport is attributable to the large anisotropic thermal motions of oxygen atoms, the presence of oxygen vacancies, and the formation of oxide-ion conducting layers in the crystal structure. The present finding of high oxide-ion conductivity in rare-earth-free CsBi 2 Ti 2 NbO 10−δ suggests the potential of Dion-Jacobson phases as a platform to identify superior oxide-ion conductors.

Chemical doping is one of the most important strategies for tuning electrical properties of semiconductors, particularly thermoelectric materials. Generally, the main role of chemical doping lies in optimizing the carrier concentration, but there can potentially be other important effects. Here, we show that chemical doping plays multiple roles for both electron and phonon transport properties in half-Heusler thermoelectric materials. With ZrNiSn-based half-Heusler materials as an example, we use high-quality single and polycrystalline crystals, various probes, including electrical transport measurements, inelastic neutron scattering measurement, and first-principles calculations, to investigate the underlying electron-phonon interaction. We find that chemical doping brings strong screening effects to ionized impurities, grain boundary, and polar optical phonon scattering, but has negligible influence on lattice thermal conductivity. Furthermore, it is possible to establish a carrier scattering phase diagram, which can be used to select reasonable strategies for optimization of the thermoelectric performance.

We study field induced quantum phase in weakly-coupled ferromagnetic frustrated chain LiCuVO 4 by neutron diffraction technique. A new incommensurate magnetic peak is observed at H ≥ 8.5 T. The field dependent propagation vector is identified with the spin density wave correlation in the theoretically predicted magnetic quadrupole order. Quantum fluctuation, geometrical frustration, and interchain interaction induce the exotic spin density wave longrange order in the insulating magnet. KEYWORDS: ferromagnetic frustrated chain, nematic state, spin density waveOne of hot topics in condensed matter science is to search a spin liquid 1) that exhibits order not in conventional two spin correlation but in others such as magnetic multipole 2) or spin chirality. 3) 1D frustrated spin chain with ferromagnetic nearest neighbor interaction (J 1 ) and antiferromagnetic next nearest neighbor interaction (J 2 ) is a zoo of such novel states.While in case of the classical spin the spontaneous rotational symmetry breaking induces spiral long-range order (LRO) for |J 1 |/J 2 < 4, those of quantum spin does not exhibit the LRO because of Mermin-Wagner theorem. 4) Instead solely the spin chirality, κ = S i × S j does order with Z 2 symmetry broken and vector chiral (VC) phase appears. 5,6) Applying magnetic field makes the system more complex and interesting. At the field close to the ferromagnetic polarized phase, a pair of magnons form bound state 7) and its Bose condensation at around q = π induces quasi-LRO of the magnetic quadrupole. 8) The quadrupole phase is characterized by the following longitudinal spin and transverse nematic correlations, 9)The former exhibits magnitude modulation with the characteristic wave vector 2k F = 2πρ, where ρ is the density of bound two-magnon, ρ = 1/2(1/2− S z ). A z , A m , andà m are positive

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