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Register a new userA protonated brownmillerite electrolyte for superior low-temperature proton conductivity
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Design novel solid oxide electrolyte with enhanced ionic conductivity forms one of the Holy Grails in the field of materials science due to its great potential for wide range of energy applications. Conventional solid oxide electrolyte typically requires elevated temperature to activate the ionic transportation, while it has been increasing research interests to reduce the operating temperature due to the associated scientific and technological importance. Here, we report a conceptually new solid oxide electrolyte, HSrCoO2.5, which shows an exceptional enhanced proton conductivity at low temperature region (from room temperature to 140 oC). Combining both the experimental results and corresponding first-principles calculations, we attribute these intriguing properties to the extremely-high proton concentration as well as the well-ordered oxygen vacancy channels inherited from the novel crystalline structure of HSrCoO2.5. This result provides a new strategy to design novel solid oxide electrolyte with excellent proton conductivity for wide ranges of energy-related applications.
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The low-temperature thermal conductivity in polycrystalline graphene is theoretically studied. The contributions from three branches of acoustic phonons are calculated by taking into account scattering on sample borders, point defects and grain boundaries. Phonon scattering due to sample borders and grain boundaries is shown to result in a $T^{alpha}$-behaviour in the thermal conductivity where $alpha$ varies between 1 and 2. This behaviour is found to be more pronounced for nanosized grain boundaries. PACS: 65.80.Ck, 81.05.ue, 73.43.Cd
This article presents studies on low-field electrical conduction in the range 4-to-300 K for a ultrafast material: InGaAs:ErAs grown by molecular beam epitaxy. The unique properties include nano-scale ErAs crystallines in host semiconductor, a deep Fermi level, and picosecond ultrafast photocarrier recombination. As the temperature drops, the conduction mechanisms are in the sequence of thermal activation, nearest-neighbor hopping, variable-range hopping, and Anderson localization. In the low-temperature limit, finite-conductivity metallic behavior, not insulating, was observed. This unusual conduction behavior is explained with the Abrahams scaling theory.
We describe measurements of 100 nK temperature oscillations at room temperature, driven at the complex interface between p-doped Germanium, a nm size metal layer, and an electrolyte. We show that heat is deposited at this interface by thermoelectric effects, however the precise microscopic mechanism remains to be established. The temperature measurement is accomplished by observing the modulation of black body radiation from the interface. We argue that this geometry offers a method to study molecular scale dissipation phenomena. The Debye layer on the electrolyte side of the interface controls much of the dynamics. Interpreting the measurements from first principles, we show that in this geometry the Debye layer behaves like a low frequency transmission line.
Electrolytes as nanostructured materials are very attractive for batteries or other types of electronic devices. (PEO)8ZnCl2 polymer electrolytes and nanocomposites (PEO)8ZnCl2/TiO2 were prepared from PEO and ZnCl2 and with addition of TiO2 nanograins. The influence of TiO2 nanograins was studied by small-angle X-ray scattering (SAXS) simultaneously recorded with wide-angle X-ray scattering (WAXS) and differential scanning calorimetry (DSC) at the synchrotron ELETTRA. It was shown by previous impedance spectroscopy (IS) that the room temperature conductivity of nanocomposite polymer electrolyte increased more than two times above 65oC, relative to pure composites of PEO and salts. The SAXS/DSC measurements yielded insight into the temperature-dependent changes of the grains of the electrolyte as well as to differences due to different heating and cooling rates. The crystal structure and temperatures of melting and crystallization of the nanosize grains was revealed by the simultaneous WAXS measurements.
We report on a novel approach to synthesize cubic-phase fast ionic conducting garnet-type solid state electrolytes based on Bi doped Li7La3Zr2O12 (LLZO). Bi aliovalent substitution into LLZO utilizing the Pechini processing method is successfully employed to synthesize Li7-xLa3Zr2-xBixO12 compounds. Ionic conductivities up to 2.0 x 10-4 S/cm are achieved in structures not fully densified. Cubic phase Li6La3ZrBiO12 powders are generated in the temperature range from 650 {deg}C to 900 {deg}C in air. In contrast, in the absence of Bi and under identical synthesis conditions, the cubic garnet phase of Li7La3Zr2O12 is not formed below 700 {deg}C while a transformation to the tetragonal phase is observed at 900 {deg}C for the un-doped compound. The critical role of Bi in lowering the formation temperature of the garnet cubic phase and the improvements in ionic conductivity is investigated in this work through microstructural studies and AC impedance measurements. We ascribe the effect of Bi doping in achieving these remarkable improvements to significant enhancements at lower temperatures in the kinetics of the solid-state reaction resulting in explosive grain growth and densification of the garnet. Moreover, XAS is utilized to identify the specific atomic site where Bi is incorporated in the LLZO garnet crystalline structure.
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