Prospective Cohort Study

Energy production and storage have become key issues concerning our welfare in daily life. Present challenges for batteries are twofold. In the first place, the increasing demand for powering systems of portable electronic devices and zero-emission vehicles stimulates research towards high energy and high voltage systems. In the second place, low cost batteries are required in order to advance towards smart electric grids that integrate discontinuous energy flow from renewable sources, optimizing the performance of clean energy sources. Na-ion batteries can be the key for the second point, because of the huge availability of sodium, its low price and the similarity of both Li and Na insertion chemistries. In spite of the lower energy density and voltage of Na-ion based technologies, they can be focused on applications where the weight and footprint requirement is less drastic, such as electrical grid storage. Much work has to be done in the field of Na-ion in order to catch up with Li-ion technology. Cathodic and anodic materials must be optimized, and new electrolytes will be the key point for Na-ion success. This review will gather the up-to-date knowledge about Na-ion battery materials, with the aim of providing a wide view of the systems that have already been explored and a starting point for the new research on this battery technology.

Na-ion batteries, recent advances and present challenges to become low cost energy storage systems

The General Utility Lattice Program (GULP) has been extended to include the ability to simulate polymers and surfaces, as well as adding many other new features, and the current status of the program is fully documented. Both the background theory is described, as well as providing a concise review of some of the previous applications in order to demonstrate the range of its use. Examples are presented of work performed using the new compatibilities of the software, including the calculation of Born effective charges, mechanical properties as a function of applied pressure, calculation of frequency-dependent dielectric data, surface reconstructions of calcite and the performance of a linear-scaling algorithm for bond-order potentials.

The general utility lattice program (GULP)

Although known since the late 19th century, organic–inorganic perovskites have recently received extraordinary research community attention because of their unique physical properties, which make them promising candidates for application in photovoltaic (PV) and related optoelectronic devices. This review will explore beyond the current focus on three-dimensional (3-D) lead(II) halide perovskites, to highlight the great chemical flexibility and outstanding potential of the broader class of 3-D and lower dimensional organic-based perovskite family for electronic, optical, and energy-based applications as well as fundamental research. The concept of a multifunctional organic–inorganic hybrid, in which the organic and inorganic structural components provide intentional, unique, and hopefully synergistic features to the compound, represents an important contemporary target.

Organic–Inorganic Perovskites: Structural Versatility for Functional Materials Design

Synthesis, properties, and applications of magnetic iron oxide nanoparticles

The K2NiF4 phases La1.5+xSr0.5−xCo0.5Ni0.5O4(+δ) (x = 0, 0.2) have been prepared by solid state reactions and structurally characterized by X-ray and neutron powder diffraction. The reduction behaviour, the magnetic properties and the electronic properties of these materials have also been examined. Oxygen hyperstoichiometry has been achieved in the lanthanum-rich phase La1.7Sr0.3Co0.5Ni0.5O4.08 with retention of the tetragonal symmetry. The excess oxygen occupies the ideal interstitial (0, 0.5, 0.25) sites of the tetragonal structure. The materials withstand reducing conditions (10% H2–N2) up to 800 °C via reduction of the B-site oxidation state to the divalent state (Ni2+/Co2+) and formation of oxide-ion vacancies within the equatorial planes of the structure. Formation of Ni1+ in these materials under reducing conditions is suggested to account for the oxygen stoichiometry and the magnetic behaviour of La1.5Sr0.5Co0.5Ni0.5O3.70. The electrical conductivity of the oxygen-rich semiconductor materials reaches a SOFC applicable limit (>100 S cm−1) at elevated temperatures.

Synthesis and characterization of La1.5+xSr0.5−xCo0.5Ni0.5O4±δ (x = 0, 0.2)

The heat capacity of several sintered specimens of YBa2Cu3O7-y, the high-temperature superconductor, has been measured from 1.5 to 10 K in magnetic fields up to 4.5 T. Part of the low-temperature anomaly in the heat capacity is ascribed to very small concentrations of localised Cu++ spins. There is a dependence of heat capacity on field which is consistent with a contribution from the electrons in flux-line cores but other features of the results are not yet understood.

Measurements of the low-temperature heat capacity of YBa2Cu3O7-y in magnetic fields up to 4.5 T

The structural effects of Zn and Fe substitutions in LaBa2Cu3O7−x have been examined using time-of-flight neutron powder diffraction, and compared with previous data relating to similar studies of YBa2Cu3O7−x. Although the Fe and Zn ions display a similar site preference (for Cu(1) and Cu(2), respectively) in both systems, significant structural differences have been found. In particular, higher concentrations of dopant are possible in LaBa2Cu3O7±x (up to 25% Cu replacement by Zn and 66% replacement by Fe), and superconductivity is rapidly destroyed due to the incorporationof additional structural defects. For Zn substitutions, a significant concentration of vacancies on the O(4) sites is introduced, whereas Fe substitutions result in a gradual increase in structural disoder of a more general type. Evidence for this disorder is found on both the oxygen sublattice, e.g. partial filling of sites in the La plane at z = 1 2 , and the cation sublattice, with some intermixing of the La and Ba ions.

The effects of partial substitutions of Zn and Fe on the Cu sites in LaBa2Cu3O7±x, and a comparison with similar substitutions in YBa2Cu3O7−x

Pulsed laser ablation has been used to fabricate La2CuO4 thin films. Superconducting properties have been successfully induced in the films by an ex-situ, post-ablation annealing process in F2 gas resulting in a Tc (onset) of 36 K. The presence of two slightly different c-axis expanded phases in the X-ray diffraction data of the fluorinated films implies a degree of inhomogeneity in F2 uptake. Critical current densities (Jc) and the irreversibility line have been established from hysteresis cycles. A Jc of ∼ 106 A cm−2 for a typical film was observed at 10 K in zero field.

Induction of superconductivity in pulsed laser ablated La2CuO4 thin films by post-deposition fluorination

Ce2MnN3F2−δ has been synthesised via low-temperature fluorination of the ternary nitride Ce2MnN3. To the best of our knowledge, Ce2MnN3F2−δ is the first quaternary nitride-fluoride to be reported. The reaction of Ce2MnN3 with 10% F2/N2 at 95–115 °C yields the fluorinated phase Ce2MnN3F2−δ, with tetragonal symmetry (P4/nmm a = 3.8554(4) A and c = 13.088(4) A based on neutron powder diffraction), accompanied by starting material. Rietveld refinement supports a staged fluorine insertion reaction (into alternate rocksalt layers) to give a product with stoichiometry Ce2MnN3F2−δ. A comparison with the formation of Sr2TiO3F2 and the isostructural LaSrMnO4F indicates that two F− anions are inserted but no F−/N3− substitution takes place. Magnetic susceptibility measurements show a transition from Pauli paramagnetic behaviour, in Ce2MnN3, to paramagnetic behaviour upon fluorination. The effective magnetic moment in Ce2MnN3F2−δ, μeff = 5.38 μB, is consistent with an intermediate value between that of Mn3+ (4.9 μB) and Mn2+ (5.9 μB) supporting the proposed stoichiometry, Ce2MnN3F2−δ.

Colin Greaves

Papers

Synthesis and characterization of La1.5+xSr0.5−xCo0.5Ni0.5O4±δ (x = 0, 0.2)

Measurements of the low-temperature heat capacity of YBa2Cu3O7-y in magnetic fields up to 4.5 T

The effects of partial substitutions of Zn and Fe on the Cu sites in LaBa2Cu3O7±x, and a comparison with similar substitutions in YBa2Cu3O7−x

Induction of superconductivity in pulsed laser ablated La2CuO4 thin films by post-deposition fluorination

Synthesis and characterisation of the quaternary nitride-fluoride Ce2MnN3F(2-delta).