Glass and glass-ceramic samples of metastable lithium thiophosphates with compositions of 70Li(2)S-30P(2)S(5) and Li7P3S11 were controllably prepared by using a rapid assisted-microwave procedure in under 30 min. The rapid preparation times and weak coupling of the evacuated silica ampules with microwave radiation ensure minimal reactivity of the reactants and the container. The microwave-prepared samples display comparable conductivity values with more conventionally prepared (melt quenched) glass and glass-ceramic samples, on the order of 0.1 and 1 mS cm(-1) at room temperature, respectively. Rietveld analysis of synchrotron X-ray diffraction data acquired with an internal standard quantitatively yields phase amounts of the glassy and amorphous components, establishing the tunable nature of the microwave preparation. X-ray photoelectron spectroscopy and Raman spectroscopy confirm the composition and the appropriate ratios of isolated and corner-sharing tetrahedra in these semicrystalline systems. Solid-state Li-7 nuclear magnetic resonance (NMR) spectroscopy resolves the seven crystallographic Li sites in the crystalline compound into three main environments. The diffusion behavior of these Li environments as obtained from pulsed-field gradient NMR methods can be separated into one slow and one fast component. The rapid and tunable approach to the preparation of high quality "Li7P3S11" samples presented here coupled with detailed structural and compositional analysis opens the door to new and promising metastable solid electrolytes.

This work describes an experimental study of a two layer active magnetic regenerator with varying transition temperature spacing. The transition temperature of the materials is based on the specific heat peak of the materials. A transition temperature based on the average of the heating and cooling curves at zero Tesla field value is used to refer to the materials throughout this paper. This study uses five Mn-Fe-Si-P materials with transition temperatures of 294.6 K, 292.3K, 290.7K, 282.5K and 281.4K. Six different regenerators are tested. A reference configuration is tested using the 294.6K material a hot side layer and with a second passive layer of lead spheres as cold side layer. Followed by four configurations that use the same 294.6K material as hot side layer, but where each configuration uses a different cold side material. For the second active layer the materials are used in sequence; 292.3K, 290.7K, 282.5 K and 281.4K. Lastly, a sixth configuration uses the 292.3 K and 282.5 K materials. For each configuration, the temperature span is measured for rejection temperatures from 40 degrees C to 9 degrees C and at 0W and 2W applied load. Experimental results for temperature span and exergetic cooling power are compared based on the differences from the reference configuration. Materials are analysed based on material performance metrics such as peak adiabatic temperature change, peak entropy change and RCP(s) values. For the cases considered, a closer transition temperature spacing generally gives a greater temperature span and exergetic cooling power than further spaced materials, even when the combined materials have comparatively lower performance metrics. When two materials with higher RCP(s) values with large transition temperature spacing are compared to materials with lower RCP(s) values but, closer transition temperature spacing a higher exergetic cooling power and temperature span is found for the latter.

Rapid preparation utilizing assisted microwave heating permits significantly shorter preparation times for magnetocaloric compounds in the (Mn,Fe)2(P,Si) family, specifically samples of (Mn,Fe)2-δP0.5Si0.5 with starting compositions of δ = 0, 0.06, and 0.12. To fully understand the effects of processing and composition changes on structure and properties, these materials are characterized using synchrotron powder diffraction, neutron powder diffraction, electron microprobe analysis (EMPA), X-ray fluorescence (XRF), and magnetic measurements. The diffraction analysis reveals that increasing δ results in decreasing amounts of the common Heusler (Mn,Fe)3Si secondary phase. EMPA shows (Mn,Fe)2(P,Si) in all three samples to be Mn and P rich, whereas XRF demonstrates that the bulk material is Mn rich yet P deficient. Increasing δ brings the Mn/Fe and P/Si ratios closer to their starting values. Measurements of magnetic properties show an increase in saturation magnetization and ordering temperature with increasing δ, consistent with the increase in Fe and Si contents. Increasing δ also results in a decrease in thermal hysteresis and an increase in magnetic entropy change, the latter reaching values close to what have been previously reported on samples that take much longer to prepare.

Using atomic layer deposition of Al2O3 coating, improved high-voltage cycling stability has been demonstrated for the layered nickelmanganesecobalt pseudoternary oxide, LiNi0.4Mn0.4Co0.2O2. To understand the effect of the Al2O3 coating, we have utilized electrochemical impedance spectroscopy, operando synchrotron-based X-ray diffraction, and operando X-ray absorption near edge fine structure spectroscopy to characterize the structure and chemistry evolution of the LiNi0.4Mn0.4Co0.2O2 cathode during cycling. Using this combination of techniques, we show that the Al2O3 coating successfully mitigates the strong side reactions of the active material with the electrolyte at higher voltages (>4.4 V), without restricting the uptake and release of Li ions. The impact of the Al2O3 coating is also revealed at beginning of lithium deintercalation, with an observed delay in the evolution of oxidation and coordination environment for the Co and Mn ions in the coated electrode due to protection of the surface. This protection prevents the competing side reactions of the electrolyte with the highly active Ni oxide sites, promoting charge compensation via the oxidation of Ni and enabling high-voltage cycling stability.

2D and 3D nanometer resolution imaging of Ge anodes during cycling show particle size-dependent fracturing and failure.

Radiation damage is a topic typically sidestepped in formal discussions of characterization techniques utilizing ionizing radiation. Nevertheless, such damage is critical to consider when planning and performing experiments requiring large radiation doses or radiation sensitive samples. High resolution, in situ transmission X-ray microscopy of Li-ion batteries involves both large X-ray doses and radiation sensitive samples. To successfully identify changes over time solely due to an applied current, the effects of radiation damage must be identified and avoided. Although radiation damage is often significantly sample and instrument dependent, the general procedure to identify and minimize damage is transferable. Here we outline our method of determining and managing the radiation damage observed in lithium sulfur batteries during in situ X-ray imaging on the transmission X-ray microscope at Stanford Synchrotron Radiation Lightsource.

We synthesized CuInS2 nanoparticles containing up to 20% Fe, Zn, and Ga to study alloying in photovoltaic absorber materials with anomalous X-ray diffraction. The colloidal synthesis allowed for detailed analysis of complex quaternary compounds. Anomalous X-ray diffraction (AXRD) was used to clarify the elemental distribution between phases. Additionally, optical spectroscopy and X-ray diffraction were used to probe the band gap and crystal phase, respectively. Substitution of Zn into wurtzite CuInS2 produced a controllable increase in the optical band gap, whereas Ga did not substitute into wurtzite CuInS2, producing no band gap change. Secondary phase precipitation of a chalcopyrite phase was observed with Fe substitution, along with a decrease of the optical band gap. This work demonstrates progress in compositional and structural analysis of quaternary chalcogenide materials using AXRD.

Rechargeable lithium-sulfur (Li-S) batteries hold great potential for high-performance energy storage systems because they have a high theoretical specific energy, low cost, and are eco-friendly. However, the structural and morphological changes during electrochemical reactions are still not well understood. In this Article, these changes in Li-S batteries are studied in operando by X-ray diffraction and transmission X-ray microscopy. We show recrystallization of sulfur by the end of the charge cycle is dependent on the preparation technique of the sulfur cathode. On the other hand, it was found that crystalline Li(2)S does not form at the end of discharge for all sulfur cathodes studied. Furthermore, during cycling the bulk of soluble polysulfides remains trapped within the cathode matrix. Our results differ from previous ex situ results. This highlights the importance of in operando studies and suggests possible strategies to improve cycle life.

Silicon is a promising anode material for Li-ion batteries due to its high theoretical specific capacity. From previous work, silicon nanowires (SiNWs) are known to undergo amorphorization during lithiation, and no crystalline Li-Si product has been observed. In this work, we use an X-ray transparent battery cell to perform in situ synchrotron X-ray diffraction on SiNWs in real time during electrochemical cycling. At deep lithiation voltages the known metastable Li(15)Si(4) phase forms, and we show that avoiding the formation of this phase, by modifying the SiNW growth temperature, improves the cycling performance of SiNW anodes. Our results provide insight on the (de)lithiation mechanism and a correlation between phase evolution and electrochemical performance for SiNW anodes.

When the complexity of a metallic compound reaches a certain level, a specific location in the structure may be critically responsible for a given fundamental property of a material while other locations may not play as much of a role in determining such a property. The first-principles theory has pinpointed a critical location in the framework of a complex intermetallic compound--Gd(5)Ge(4)--that resulted in a controlled alteration of the magnetism of this compound using precise chemical tools.

The interrelation between the specific crystallographic positions and their influence on the magnetism of neighboring atoms is examined from first principles electronic structure calculations using the Gd5Ge4 compound as a model system. The predicted preferences of the specific occupations by nonmagnetic yttrium atoms and the resulting magnetism of substituted Gd5Ge4 have been confirmed, respectively, by single crystal x-ray diffraction and magnetization experiments.

A crystallographic study and theoretical analysis of the Si/Ga site preferences in the Gd(5)Ga(x)Si(4-x) series is presented. Gd(5)Ga(x)Si(4-x) adopt the orthorhombic Gd(5)Si(4)-type structure (space group Pnma, Z = 4) with a maximum Ga content near x = 1.00, as determined by single crystal and powder X-ray diffraction. Refinements from single crystal X-ray diffraction studies of the three independent sites for Si/Ga atoms in the asymmetric unit (interslab T1, intraslab T2 and T3) reveal partial mixing of these elements, with a clear preference for Ga substitution at the interslab T1 sites. To investigate site preferences of Si/Ga atoms, first-principles electronic structure calculations were carried out using the Vienna ab initio simulation package (VASP) and the Stuttgart tight-binding, linear-muffin-tin orbital program with the atomic sphere approximation (TB-LMTO-ASA). Analysis of various crystal orbital Hamilton population (COHP) curves provide some further insights into the structural tendencies and indicate the roles of both sizes and electronegativities of Ga and Si toward influencing the observed upper limit in Ga content in Gd(5)Ga(x)Si(4-x). The magnetic properties of two Gd(5)Ga(x)Si(4-x) phases are also reported: both show ferromagnetic behavior with Curie temperatures lower than that for Gd(5)Si(4).

Gd(2)Sc(3)Ge(4) adopts the ortho-rhom-bic Pu(5)Rh(4)-type structure. The crystal structure contains six sites in the asymmetric unit: two sites are statistically occupied by rare-earth atoms with Gd:Sc ratios of 0.967 (4):0.033 (4) and 0.031 (3):0.969 (3), one site (.m. symmetry) is occupied by Sc atoms, and three distinct sites (two of which with .m. symmetry) are occupied by Ge atoms. The rare-earth atoms form two-dimensional slabs with Ge atoms occupying the trigonal-prismatic voids.

A crystallographic Study of the Nd/Er site preferences in the Nd(5-x)Er(x)Tt(4) (Ti = Si, Ge) series prepared by high-temperature methods is presented. For Nd5-xErxSi4, phases with x <= 1.0 adopt the tetragonal Zr5Si4-type structure. On the other hand, phases in the composition range of 2.0 <= x <= 5.0 exhibits the Gd5Si4-type Structure. For all silicides, all silicon atoms belong to Si-Si dimers. In the Nd5-xErxGe4 system, phases with x < 3.2 and x = 4.0 adopt the orthorhombic Sm5Ge4-type Structure. For the composition range of 3.2 <= x <= 4.0, a monoclinic U2Mo3Si4-type structure (space group P2(1)/c) Occurs as the majority phase. This monoclinic Structure, until recently, wits not reported for similar RE5T4 systems, and differs from the known monoclinic Gd5Si2Ge2-type (space group P2(1)/a) because till Ge center dot center dot center dot Ge contacts between slabs tire equivalent. The structural relationships between the Zr5Si4-type, Gd5Si4-type, Sm5Ge4-type, and U2Mo3Si4-type structures tire discussed. Single crystal refinements of the metal atom occupancies for the three different metal sites in the asymmetric unit of all structure types reveal a partially ordered nonstatistical arrangement of neodymium and erbium atoms. The magnetic properties of some Nd5-xErxGe4 phases are also reported. Nd4ErGe4 shows an anti-ferromagnetic-type transition similar to Gd5Ge4. As the erbium concentration increases (2 <= x <= 4), these phases exhibit, at least, ferromagnetic-type ordering.

Optical and electron micrographs reveal that R5(SixGe1–x)3-type compounds, existing as thin plates, are prevalent in R5(Six,Ge1–x)4 compound systems. The purpose of this research is an attempt to improve understanding of the formation of these thin plates by extending microstructural examination to other R5(SixGe1–x)4 systems where formation of R5(SixGe1–x)3 compounds may face additional constraints. Ho5(Si0.8Ge0.2)4, Ho5Ge4, Yb5Ge4, Gd5Ge3.5Sb0.5, Gd5Ge3Ga and Gd5Ge3Sn alloys were examined by X-ray powder diffraction, scanning and transmission electron microscopy and energy dispersive spectroscopy. R5(SixGe1–x)3-type thin plates were observed in all alloys studied except for the Sb substituted system, which may be related to deviation of the valence electron concentration from normal R5(SixGe1–x)4 systems. Calculations of lattice misfit based on various assumptions indicate that the formation of thin plates is less sensitive to small lattice distortion than initially believed, and also appears fairly insensitive to slight composition variations.

Temperature-dependent, single crystal and powder X-ray diffraction studies as well as magnetization, and heat capacity measurements were carried out on two phases of the Gd5GaxGe4−x system: for x=0.7 and 1.0. Gd5Ga0.7Ge3.3 shows three structure types as a function of temperature: (i) from 165K to room temperature, the orthorhombic Sm5Ge4-type structure exists; (ii) below 150K, it transforms to a orthorhombic Gd5Si4-type structure; and (iii) a monoclinic Gd5Si2Ge2-type component is observed for the intermediate temperature range of 150K≤T≤165K. This is the first time that all these three structure types have been observed for the same composition. For Gd5Ga1.0Ge3.0, the room temperature phase belongs to the orthorhombic Pu5Rh4-type structure with interslab contacts between main group atoms of 2.837(4)Å. Upon heating above 523K, it transforms to a Gd5Si4-type structure with this distance decreasing to 2.521(7)Å before decomposing above 573K.

The binary, ternary and multicomponent intermetallic compounds of rare-earth metals (RE) with group 14 elements (Tt) at the RE5Tt4 stoichiometry have been known for over 30 years, but only in the past decade have these materials become a gold mine for solid-state chemistry, materials science and condensed matter physics. It all started with the discovery of a giant magnetocaloric effect in Gd5Si2Ge2, along with other extraordinary magnetic properties, such as a colossal magnetostriction and giant magnetoresistance. The distinctiveness of this series is in the remarkable flexibility of the chemical bonding between well-defined, subnanometer-thick slabs and the resultant magnetic, transport, and thermodynamic properties of these materials. This can be controlled by varying either or both RE and Tt elements, including mixed rare-earth elements on the RE sites and different group 14 (or T = group 13 or 15) elements occupying the Tt sites. In addition to chemical means, the interslab interactions are also tunable by temperature, pressure, and magnetic field. Thus, this system provides a splendid 'playground' to investigate the interrelationships among composition, structure, physical properties, and chemical bonding. The work presented in this dissertation involving RE5T4 materials has resulted in the successful synthesis, characterization, property measurements, and theoretical analyses of various new intermetallic compounds. The results provide significant insight into the fundamental magnetic and structural behavior of these materials and help us better understand the complex link between a compound's composition, its observed structure, and its properties.

A crystallographic study and theoretical assessment of the Gd/Y site preferences in the Gd 5- x Y x Tt 4 ( Tt = Si, Ge) series prepared by high-temperature methods is presented. All structures for the Gd 5- x Y x Si 4 system belong to the orthorhombic, Gd 5Si 4-type (space group Pnma). For the Gd 5- x Y x Ge 4 system, phases with x < 3.6 and x >or= 4.4 adopt the orthorhombic, Sm 5Ge 4-type structure. For the composition range of 3.6