Compositional and structural control in LLZO solid electrolytes.

Garnet-based solid-state electrolytes (SSEs) represent a promising class of materials for next-generation batteries with improved safety and performance. However, lack of control over the composition and crystal structure of the well-known LiLaZrO (LLZO) garnet material has led to poor reproducibility with a wide range of ionic conductivities reported in the literature. In this study, the role of precursor homogeneity in controlling the compositional and structural evolution of Al-doped LLZO is explored.

THz/Far infrared synchrotron observations of superlattice frequencies in MgB.

THz/Far Infrared synchrotron absorption experiments on pure and doped MgB samples show that the absorption spectral weight at low wavenumber (, <110 cm) evolves as the temperature is reduced to 10 K. Distinct spectral peak intensities increase as the temperature of MgB and doped MgB approaches, and then crosses, the superconducting transition temperature. These experimental data suggest a strong link to superconductivity induced by subtle shifts in structural symmetry.

Validating the Electronic Structure of Vanadium Phosphate Cathode Materials.

Investigation of the electronic structure of contending battery electrode materials is an essential step for developing a detailed mechanistic understanding of charge-discharge properties. Herein, we use synchrotron soft X-ray absorption spectroscopy (XAS) in combination with complementary experiments and density functional theory calculations to map the electronic structure, band positioning, and band gap of prototype vanadium(III) phosphate cathode materials, NaV(PO), LiV(PO), and KV(PO)·HO, for alkali-ion rechargeable batteries. XAS fluorescence yield and electron yield measurements reveal substantial variation in surface-to-bulk atomic structure, vanadium oxidation states, and density of oxygen hole states across all samples.

Effects of Al substitution by Si in TiAlC nanolaminate.

Recently, a series of high-purity Ti(AlSi)C solid solutions with new compositions (x = 0.0, 0.2, 0.

Synthesis and Characterization of a Novel Hydrated Layered Vanadium(III) Phosphate Phase KV(PO)·HO: A Functional Cathode Material for Potassium-Ion Batteries.

Hydrated vanadium(III) phosphate, KV(PO)·HO, has been synthesized by a facile aqueous hydrothermal reaction. The crystal structure of the compound is determined using X-ray diffraction (XRD) analysis aided by density functional theory (DFT) computational investigation. The structure contains layers of corner-sharing VO octahedra connected by corner and edge-sharing PO tetrahedra with a hydrated K ion interlayer.

Re-evaluation of experimental measurements for the validation of electronic band structure calculations for LiFePO and FePO.

Experimental measurements used to validate previous electronic band structure calculations for olivine LiFePO and its delithiated phase, FePO, have been re-investigated in this study. Experimental band gaps of LiFePO and FePO have been determined to be 6.34 eV and 3.

Phonon anomalies predict superconducting T(c) for AlB2-type structures.

We show that the well-known Kohn anomaly predicts Tc for ordered AlB2-type structures. We use ab initio density functional theory to calculate phonon dispersions for Mg1-xAlxB2 compositions and identify a phonon anomaly with magnitude that predicts experimental values of Tc for all x. Key features of these anomalies correlate with the electronic structure of Mg1-xAlxB2.

Coherent phonon decay and the boron isotope effect for MgB2.

Ab initio DFT calculations for the phonon dispersion (PD) and the phonon density of states (PDOS) of the two isotopic forms ((10)B and (11)B) of MgB2 demonstrate that use of a reduced symmetry super-lattice provides an improved approximation to the dynamical, phonon-distorted P6/mmm crystal structure. Construction of phonon frequency plots using calculated values for these isotopic forms gives linear trends with integer multiples of a base frequency that change in slope in a manner consistent with the isotope effect (IE). Spectral parameters inferred from this method are similar to that determined experimentally for the pure isotopic forms of MgB2.

Phonon modes of MgB2: super-lattice structures and spectral response.

Micrometre-sized MgB2 crystals of varying quality, synthesized at low temperature and autogenous pressure, are compared using a combination of Raman and infra-red (IR) spectroscopy. These data, which include new peak positions in both spectroscopies for high quality MgB2, are interpreted using DFT calculations on phonon behaviour for symmetry-related structures. Raman and IR activity additional to that predicted by point group analyses of the P6/mmm symmetry are detected.

Synthesis of MgB₂ at Low Temperature and Autogenous Pressure.

High quality, micron-sized interpenetrating grains of MgB₂, with high density, are produced at low temperatures (~420 °C < < ~500 °C) under autogenous pressure by pre-mixing Mg powder and NaBH₄ and heating in an Inconel 601 alloy reactor for 5-15 h. Optimum production of MgB₂, with yields greater than 75%, occurs for autogenous pressure in the range 1.0 MPa to 2.