Encoding CO Adsorption in Sodium Zirconate by Neutron Diffraction.

Recent research into sodium zirconate as a high-temperature CO sorbent has been extensive, but detailed knowledge of the material's crystal structure during synthesis and carbon dioxide uptake remains limited. This study employs neutron diffraction (ND), thermogravimetric analysis (TGA), and X-ray diffraction (XRD) to explore these aspects. An improved synthesis method, involving the pre-drying and ball milling of raw materials, produced pure samples with average crystal sizes of 37-48 nm in the monoclinic phase.

Alloying and Doping Control in the Layered Metal Phosphide Thermoelectric CaCuP.

We recently identified CaCuP as a potential low cost, low density thermoelectric material, achieving = 0.5 at 792 K. Its performance is limited by a large lattice thermal conductivity, , and by intrinsically large p-type doping levels.

Oxygen Migration Pathways in Layered LnBaCoO (Ln = La - Y) Perovskites.

Layered LnBaCoO perovskites are important mixed ionic-electronic conductors, exhibiting outstanding catalytic properties for the oxygen evolution/reduction reaction. These phases exhibit considerable structural complexity, in particular, near room temperature, where a number of oxygen vacancy ordered superstructures are found. This study uses bond valence site energy calculations to demonstrate the key underlying structural features that favor facile ionic migration.

Revisiting Solid-Solid Phase Transitions in Sodium and Potassium Tetrafluoroborate for Thermal Energy Storage.

In situ synchrotron powder X-ray diffraction (PXRD) study was conducted on sodium and potassium tetrafluoroborate (NaBF and KBF) to elucidate structural changes across solid-solid phase transitions over multiple heating-cooling cycles. The phase transition temperatures from diffraction measurements are consistent with the differential scanning calorimetry data (∼240 °C for NaBF and ∼290 °C for KBF). The crystal structure of the high-temperature (HT) NaBF phase was determined from synchrotron PXRD data.

Mechanistic Insights into the Formation of Thermoelectric TiNiSn from In Situ Neutron Powder Diffraction.

Half-Heusler alloys are leading contenders for application in thermoelectric generators. However, reproducible synthesis of these materials remains challenging. Here, we have used in situ neutron powder diffraction to monitor the synthesis of TiNiSn from elemental powders, including the impact of intentional excess Ni.

New sustainable ternary copper phosphide thermoelectrics.

The thermoelectric performance of ACuP (A = Mg and Ca) with abundant elements and low gravimetric density is reported. Both systems are p-type doped by intrinsic Cu vacancy defects, have large power factors and promising figures of merit, reaching = 0.5 at 800 K.

A Correlative Study of Interfacial Segregation in a Cu-Doped TiNiSn Thermoelectric half-Heusler Alloy.

The performance of thermoelectric materials depends on both their atomic-scale chemistry and the nature of microstructural details such as grain boundaries and inclusions. Here, the elemental distribution throughout a TiNiCuSn thermoelectric material has been examined in a correlative study deploying atom-probe tomography (APT) and electron microscopies and spectroscopies. Elemental mapping and electron diffraction reveal two distinct types of grain boundary that are either topologically rough and meandering in profile or more regular and geometric.

Insights into Oxygen Migration in LaBaCoO Perovskites from Neutron Powder Diffraction and Bond Valence Site Energy Calculations.

Layered cobalt oxide perovskites are important mixed ionic and electronic conductors. Here, we investigate LaBaCoO using neutron powder diffraction. This composition is unique because it can be prepared in cubic, layered, and vacancy-ordered forms.

BaBiCoRuO (0.0 ≤ ≤ 0.6) Hexagonal Double-Perovskite-Type Oxides as Promising p-Type Thermoelectric Materials.

A new series of BaBiCoRuO (0.0 ≤ ≤ 0.6) hexagonal double perovskite oxides have been synthesized by a solid-state reaction method by substituting Ba with Bi.

Atom Probe Tomography of a Cu-Doped TiNiSn Thermoelectric Material: Nanoscale Structure and Optimization of Analysis Conditions.

Cu-doping and crystallographic site occupations within the half-Heusler (HH) TiNiSn, a promising thermoelectric material, have been examined by atom probe tomography. In particular, this investigation aims to better understand the influence of atom probe analysis conditions on the measured chemical composition. Under a voltage-pulsing mode, atomic planes are clearly resolved and suggest an arrangement of elements in-line with the expected HH (F-43m space group) crystal structure.

Decoupling Lattice and Magnetic Instabilities in Frustrated CuMnO.

The AMnO delafossites (A = Na, Cu) are model frustrated antiferromagnets, with triangular layers of Mn spins. At low temperatures ( = 65 K), a 2/ → 1̅ transition is found in CuMnO, which breaks frustration and establishes magnetic order. In contrast to this clean transition, A = Na only shows short-range distortions at .

Effect of light scattering on upconversion photoluminescence quantum yield in microscale-to-nanoscale materials.

Scattering affects excitation power density, penetration depth and upconversion emission self-absorption, resulting in particle size -dependent modifications of the external photoluminescence quantum yield (ePLQY) and net emission. Micron-size NaYF:Yb, Er encapsulated phosphors (∼4.2 µm) showed ePLQY enhancements of >402%, with particle-media refractive index disparity (Δn): 0.

Spin-chain correlations in the frustrated triangular lattice material CuMnO.

The Ising triangular lattice remains the classic test-case for frustrated magnetism. Here we report neutron scattering measurements of short range magnetic order in CuMnO, which consists of a distorted lattice of Mnspins with single-ion anisotropy. Physical property measurements on CuMnOare consistent with 1D correlations caused by anisotropic orbital occupation.

Toward New Thermoelectrics: Tin Selenide/Modified Graphene Oxide Nanocomposites.

New nanocomposites have been prepared by combining tin selenide (SnSe) with graphene oxide (GO) in a simple aqueous solution process followed by ice templating (freeze casting). The resulting integration of SnSe within the GO matrix leads to modifications of electrical transport properties and the possibility of influencing the power factor ( σ). Moreover, these transport properties can then be further improved (, σ increased) by functionalization of the GO surface to form modified nanocomposites (SnSe/GO) with enhanced power factors in comparison to unmodified nanocomposites (SnSe/GO) and "bare" SnSe itself.

Topotactic anion-exchange in thermoelectric nanostructured layered tin chalcogenides with reduced selenium content.

Anion exchange has been performed with nanoplates of tin sulfide (SnS) "soft chemical" organic-free solution syntheses to yield layered pseudo-ternary tin chalcogenides on a 10 g-scale. SnS undergoes a topotactic transformation to form a series of S-substituted tin selenide (SnSe) nano/micro-plates with tuneable chalcogenide composition. SnSSe nanoplates were spark plasma sintered into phase-pure, textured, dense pellets, the of which has been significantly enhanced to ≈1.

Impact of Interstitial Ni on the Thermoelectric Properties of the Half-Heusler TiNiSn.

TiNiSn is an intensively studied half-Heusler alloy that shows great potential for waste heat recovery. Here, we report on the structures and thermoelectric properties of a series of metal-rich TiNiSn compositions prepared via solid-state reactions and hot pressing. A general relation between the amount of interstitial Ni and lattice parameter is determined from neutron powder diffraction.

Impact of Nb vacancies and p-type doping of the NbCoSn-NbCoSb half-Heusler thermoelectrics.

The half-Heuslers NbCoSn and NbCoSb have promising thermoelectric properties. Here, an investigation of the NbCoSnSb (y = 0, 0.05; 0 ≤ z ≤ 1) solid-solution is presented.

Grain-by-Grain Compositional Variations and Interstitial Metals-A New Route toward Achieving High Performance in Half-Heusler Thermoelectrics.

Half-Heusler alloys based on TiNiSn are promising thermoelectric materials characterized by large power factors and good mechanical and thermal stabilities, but they are limited by large thermal conductivities. A variety of strategies have been used to disrupt their thermal transport, including alloying with heavy, generally expensive, elements and nanostructuring, enabling figures of merit, ZT ≥ 1 at elevated temperatures (>773 K). Here, we demonstrate an alternative strategy that is based around the partial segregation of excess Cu leading to grain-by-grain compositional variations, the formation of extruded Cu "wetting layers" between grains, and-most importantly-the presence of statistically distributed interstitials that reduce the thermal conductivity effectively through point-defect scattering.

Theoretical prediction of strain tuneable quaternary spintronic Heusler compounds.

Heusler materials have attracted a large amount of attention in the development of spintronic technologies. In this issue, Wang [ (2017), , 758-768] show how strain can be used to tune the band structure of these materials.

Large-Scale Surfactant-Free Synthesis of p-Type SnTe Nanoparticles for Thermoelectric Applications.

A facile one-pot aqueous solution method has been developed for the fast and straightforward synthesis of SnTe nanoparticles in more than ten gram quantities per batch. The synthesis involves boiling an alkaline Na₂SnO₂ solution and a NaHTe solution for short time scales, in which the NaOH concentration and reaction duration play vital roles in controlling the phase purity and particle size, respectively. Spark plasma sintering of the SnTe nanoparticles produces nanostructured compacts that have a comparable thermoelectric performance to bulk counterparts synthesised by more time- and energy-intensive methods.

Facile Surfactant-Free Synthesis of p-Type SnSe Nanoplates with Exceptional Thermoelectric Power Factors.

A surfactant-free solution methodology, simply using water as a solvent, has been developed for the straightforward synthesis of single-phase orthorhombic SnSe nanoplates in gram quantities. Individual nanoplates are composed of {100} surfaces with {011} edge facets. Hot-pressed nanostructured compacts (Eg ≈0.

Ambient-Pressure Synthesis of Two New Vanadium-Based Calcium Ferrite-Type Compounds: NaV1.25Ti0.75O4 and NaVSnO4.

Two new CaFe2O4-type compounds NaV1.25Ti0.75O4 (1) and NaVSnO4 (2) have been prepared at ambient pressure and temperatures < 800 °C.

Antisite-disorder, magnetic and thermoelectric properties of Mo-rich Sr2Fe1-yMo1+yO6 (0 ≤y≤ 0.2) double perovskites.

Structure analysis using X-ray and neutron powder diffraction and elemental mapping has been used to demonstrate that nominal A-site deficient Sr(2-x)FeMoO(6-δ) (0 ≤x≤ 0.5) compositions form as Mo-rich Sr(2)Fe(1-y)Mo(1+y)O(6) (0 ≤y≤ 0.2) perovskites at high temperatures and under reducing atmospheres.

Effect of Spark Plasma Sintering on the Structure and Properties of TiZrNiSn Half-Heusler Alloys.

XNiSn (X = Ti, Zr and Hf) half-Heusler alloys have promising thermoelectric properties and are attracting enormous interest for use in waste heat recovery. In particular, multiphase behaviour has been linked to reduced lattice thermal conductivities, which enables improved energy conversion efficiencies. This manuscript describes the impact of spark plasma sintering (SPS) on the phase distributions and thermoelectric properties of TiZrNiSn based half-Heuslers.

Half-Heusler thermoelectrics: a complex class of materials.

Half-Heusler thermoelectrics first attracted interest in the late-1990s and are currently undergoing a renaissance. This has been driven by improved synthesis, processing and characterisation methods, leading to increases in the thermoelectric figure of merit and the observation of novel phenomena such as carrier filtering in nanocomposite samples. The difficulty in extracting good thermoelectric performance is at first glance surprising given the relative simplicity of the ideal crystal structure with only site occupancies and lattice parameter as crystallographic variables.