The thermal expansion coefficient of a material exhibiting negative thermal expansion above 400 degrees C, Zn2V2O7, was tuned using Mg as a substituent on the Zn site. Samples x = 0.0, 0.1, 0.2 and 0.3 were prepared using high-temperature ceramic methods. Changes to the structure and properties with Mg substitution were analyzed using Rietveld refinement of ambient and variable-temperature X-ray diffraction data (VTXRD) using synchrotron radiation. The parent structure Zn2V2O7 transitions from the alpha phase (C2/c) to the beta phase (C2/m) near 650 degrees C, and Mg substitution lowers the temperature of this transition as corroborated by differential scanning calorimetry measurements. Mg substitution allows the volume thermal expansion coefficient to be tuned from -19.80 ppm K-1 in x = 0.0 to -13.46 ppm K-1 in x = 0.3.

'Cool' pigments are a potential rapid mitigation strategy for urban areas that experience excessive heat. The impacts of this technology extend beyond infrastructure to moderate public health risks of excessive heat in vulnerable neighbourhoods. Broadly, team science and interdisciplinary collaboration are key to addressing society's urgent issues, including climate change.

Co_1-xMn_xCr_2O_4 crystallizes as a normal spinel in the cubic Fd 3m space group, and the end members have been reported to display a region of collinear ferrimagnetism as well as a low-temperature spin-spiral state with variable coherence lengths from 3 nm to 10 nm in polycrystalline samples. Here, we present the synthesis of the entire solid solution, and data showing that the ferrimagnetic ordering temperature as well as the spin-spiral lock-in temperature are tunable with the Co/Mn ratio. The peak magnetocaloric entropy change was determined to be Δ S_M = -5.63 J kg^-1 K^-1 in an applied magnetic field change of Δ H = 0 T to 5 T for the Mn end-member at the ferrimagnetic ordering temperature. Using density functional theory (DFT), we explore the shortcomings of the magnetic deformation proxy to identify trends in Δ S_M across composition in this spinel system, and explore future extensions of theory to address these discrepancies.

Co$_{1-x}$Mn$_x$Cr$_2$O$_4$ crystallizes as a normal spinel in the cubic $Fd \overline{3}m$ space group, and the end members have been reported to display a region of collinear ferrimagnetism as well as a low-temperature spin-spiral state with variable coherence lengths from 3 nm to 10 nm in polycrystalline samples. Here, we present the synthesis of the entire solid solution, and data showing that the ferrimagnetic ordering temperature as well as the spin-spiral lock-in temperature are tunable with the Co/Mn ratio. The peak magnetocaloric entropy change was determined to be $\Delta S_M$ = -5.63 J kg$^{-1}$ K$^{-1}$ in an applied magnetic field change of $\Delta H$ = 0 T to 5 T for the Mn end-member at the ferrimagnetic ordering temperature. Using density functional theory (DFT), we explore the shortcomings of the magnetic deformation proxy to identify trends in $\Delta S_M$ across composition in this spinel system, and explore future extensions of theory to address these discrepancies.

Framework oxide materials are well-known for exhibiting not only negative thermal expansion (NTE), but also demonstrating thermal expansion that can be controlled using composition as a tuning parameter. In this work, we study the intrinsic thermal expansion properties of Co _2 V _2 O _7 , which has shown bulk linear NTE, and attempt to understand how substituting Ni ^2+ for Co ^2+ will affect the thermal expansion. The isomorphic solid solution is synthesized through solid-state methods and characterized using x-ray diffraction (XRD), diffuse reflectance spectroscopy, and neutron diffraction. The size difference between Ni ^2+ and Co ^2+ as well as the polyhedral volume of each Co ^2+ metal coordination environment in the crystal structure allows Ni ^2+ to partially be directed toward one crystallographic site over the other. Variable temperature synchrotron XRD data are employed to understand intrinsic thermal expansion. Across the solid solution, no intrinsic NTE is observed at the microscopic level, yet a degree of tunability in the thermal expansion coefficient with Ni substitution is demonstrated. The disparities between the intrinsic and bulk thermal expansion properties suggest that a morphological mechanism may have resulted in NTE in the bulk.

Co$_{1-x}$Mn$_x$Cr$_2$O$_4$ crystallizes as a normal spinel in the cubic $Fd \overline{3}m$ space group, and the end members have been reported to display a region of collinear ferrimagnetism as well as a low-temperature spin-spiral state with variable coherence lengths from 3 nm to 10 nm in polycrystalline samples. Here, we present the synthesis of the entire solid solution, and data showing that the ferrimagnetic ordering temperature as well as the spin-spiral lock-in temperature are tunable with the Co/Mn ratio. The peak magnetocaloric entropy change was determined to be $\Delta S_M$ = -5.63 J kg$^{-1}$ K$^{-1}$ in an applied magnetic field change of $\Delta H$ = 0 T to 5 T for the Mn end-member at the ferrimagnetic ordering temperature. Using density functional theory (DFT), we explore the shortcomings of the magnetic deformation proxy to identify trends in $\Delta S_M$ across composition in this spinel system, and explore future extensions of theory to address these discrepancies.

MnPdGa, a compound crystallizing in the ${\mathrm{Ni}}_{2}\mathrm{In}$ structure, is a material displaying magnetic ordering near room temperature and is a potential ambient-temperature magnetocaloric. Screening based on electronic structure calculations suggest that MnPdGa may exhibit a high magnetocaloric figure of merit due to its strong magnetostructural coupling. Here we report the preparation of MnPdGa and employ high--resolution synchrotron x-ray diffraction to confirm its hexagonal ${\mathrm{Ni}}_{2}\mathrm{In}$-type structure. The zero-field ground state is shown to be a conical spin-wave state, defined by a long-range modulation of the conventional conical antiferromagnet structure. Near the Curie temperature, the measurements carried out here coupled with electronic structure calculations suggest that a fully ferromagnetic state can form at elevated temperatures under an applied field. A peak magnetocaloric entropy change $\mathrm{\ensuremath{\Delta}}{S}_{M}=\ensuremath{-}3.54\phantom{\rule{0.28em}{0ex}}\mathrm{J}\phantom{\rule{0.28em}{0ex}}{\mathrm{kg}}^{\ensuremath{-}1}\phantom{\rule{4pt}{0ex}}{\mathrm{K}}^{\ensuremath{-}1}$ ($30.1\phantom{\rule{0.16em}{0ex}}\mathrm{mJ}\phantom{\rule{0.16em}{0ex}}{\mathrm{cm}}^{\ensuremath{-}3}\phantom{\rule{0.16em}{0ex}}{\mathrm{K}}^{\ensuremath{-}1}$) is measured at ${T}_{C}\phantom{\rule{0.16em}{0ex}}=\phantom{\rule{0.16em}{0ex}}315\phantom{\rule{0.16em}{0ex}}\mathrm{K}$ at an applied field $H=5\phantom{\rule{0.16em}{0ex}}\mathrm{T}$. The exchange-driven, nontrivial magnetic structure found in MnPdGa is compared with the somewhat better-studied MnPtGa on the basis of electronic structure calculations.

Many of the promising, high-performing solid electrolytes for lithium-ion batteries are amorphous or contain an amorphous component, particularly in the Li thiophosphate Li2S-P2S5 (LPS) compositional series. An explicit study of the local structure in four samples of ostensibly identically prepared 70Li2S-30P2S5 glass reveals substantial variation in the ratio between the two main local structural units in this system: PS43- tetrahedra and P2S74- corner-sharing tetrahedral pairs. Local structural and compositional probes including Raman spectroscopy, X-ray photoelectron spectroscopy, and X-ray pair distribution function analysis are employed here to arrive at a consistent description of the relative amounts of isolated tetrahedral units, which vary by 13% across the samples measured. This local structure variation translates to differences in the activation energies measured by electrochemical impedance spectroscopy in these samples, such that the higher concentration of isolated tetrahedra corresponds to a lower activation energy. The measured temperature-dependent ionic conductivity data are compared to conductivity results across the literature reported on the same compositions, highlighting the variation in the measured activation energy for nominally identical samples. These findings have implications for the critical need to play close attention to the local structure in solid electrolytes, particularly in systems that are glasses or glass ceramics, or those that comprise any amorphous contribution.

Vacancy-ordered double perovskites are attracting significant attention due to their chemical diversity and interesting optoelectronic properties. With a view to understanding both the optical and magnetic properties of these compounds, two series of Ru-IV halides are presented; A(2)RuCl(6) and A(2)RuBr(6), where A is K, NH4, Rb or Cs. We show that the optical properties and spin-orbit coupling (SOC) behavior can be tuned through changing the A cation and the halide. Within a series, the energy of the ligand-to-metal charge transfer increases as the unit cell expands with the larger A cation, and the band gaps are higher for the respective chlorides than for the bromides. The magnetic moments of the systems are temperature dependent due to a non-magnetic ground state with J(eff)=0 caused by SOC. Ru-X covalency, and consequently, the delocalization of metal d-electrons, result in systematic trends of the SOC constants due to variations in the A cation and the halide anion.

Magnetic refrigeration, as well as waste-heat recovery, can be accomplished through the magnetocaloric effect, where temperature changes the magnetic state of a material or vice versa. Promising magnetocaloric materials display large changes in magnetic entropy (Delta S-M) upon application of a moderate magnetic field and are often associated with magnetic materials possessing some degree of magnetostructural coupling. In such compounds, the magnetic transition is coupled to some structural transition at the ordering temperature, and indicators for these are readily calculated by the magnetic deformation proxy Sigma(M). MnSb, with a Curie temperature T-C = 577 K, has a calculated magnetic deformation of Sigma(M) = 5.9% and is a promising candidate material for waste-heat recovery. The temperature dependence of structural, magnetic, and magnetocaloric properties of Mn1+xSb, where x is a tunable amount of interstitial Mn, is studied here. Excess Mn is incorporated as an interstitial whose magnetic moment is antialigned with the stoichiometric Mn, and the excess Mn has the effect of lowering T-C, such that the Curie temperature can be tuned from 577 K to nearly room temperature at 318 K for x = 0.2. For x = 0.0, 0.1, and 0.2, values of Delta S-M under a maximum magnetic field H = 5 T are found to be 3.65, 3.00, and 2.83 J K-1 kg(-1), respectively. While the maximum Delta S-M decreases with x, the high refrigerant capacity a more holistic measure of performance-is retained in this highly tunable system.

The Wadsley-Roth phase (W0.2V0.8)(3)O-7, crystallizing in a structure obtained through crystallographic shear of 3 x 3 x infinity ReO3 blocks, is a somewhat rare exemplar for this class of compounds in that it contains a relatively small amount of 4d and/or Sd transition elements. Here, we demonstrate that it functions as a high-rate, high-capacity material for lithium-ion batteries. Electrochemical insertion and deinsertion in micron-sized particles made by conventional solid-state preparation and in sub-100 nm particles made by combining sol-gel precursors with freeze-drying methods indicate good rate capabilities. The materials display high capacity-close to 300 mA h g(-1) at low rates-corresponding to the insertion of up to 1.3 Li per transition metal at voltages above 1 V. Li insertion is associated with multielectron redox for both V and W observed from ex situ X-ray photoelectron spectroscopy. The replacement of 4d and Sd elements with vanadium results in a higher voltage than seen in other, usually niobium-containing shear-structured electrode materials, and points to new opportunities for tuning voltage, electrical conductivity, and capacity in compounds in this structural class.

In the AB(4)Q(8) lacunar spinels, the electronic structure is described on the basis of inter- and intracluster interactions of tetrahedral B-4 clusters, and tuning these can lead to myriad fascinating electronic and magnetic ground states. In this work, we employ magnetic measurements, synchrotron x-ray and neutron scattering, and first-principles electronic structure calculations to examine the coupling between structural and magnetic phase evolution in GaMo4Se8, including the emergence of a skyrmionic regime in the magnetic phase diagram. We show that the competition between two distinct Jahn-Teller distortions of the room temperature cubic F (4) over bar 3m structure leads to the coexistence of the ground-state R3m phase and a metastable Imm2 phase. The magnetic properties of these two phases are computationally shown to be very different, with the Imm2 phase exhibiting uniaxial ferromagnetism and the R3m phase hosting a complex magnetic phase diagram including equilibrium Neel-type skyrmions stable from nearly T = 28 K down to T = 2 K, the lowest measured temperature. The large change in magnetic behavior induced by a small structural distortion reveals that GaMo4Se8 is an exciting candidate material for tuning unconventional magnetic properties via mechanical means.

MnPtGa crystallizes in the hexagonal ${\mathrm{Ni}}_{2}\mathrm{In}$ structure type in space group $P{6}_{3}/mmc$ and has been reported to display a ferromagnetic Curie temperature near 220K. Here we find a transition near ${T}_{C}=236$ K to a ferromagnetic state, albeit with a reduced moment from what is expected for collinear ordering. The peak magnetocaloric entropy change was determined to be $\mathrm{\ensuremath{\Delta}}{S}_{M}=\ensuremath{-}1.9\phantom{\rule{0.28em}{0ex}}\mathrm{J}\phantom{\rule{0.16em}{0ex}}{\mathrm{kg}}^{\ensuremath{-}1}\phantom{\rule{0.16em}{0ex}}{\mathrm{K}}^{\ensuremath{-}1}$ for an applied magnetic field of $H=5\phantom{\rule{0.16em}{0ex}}\mathrm{T}$ at the ferromagnetic ordering temperature. Magnetostructural coupling manifests as a change in the slope of the thermal expansion coefficients of the $c$ lattice parameter near ${T}_{C}$, with a negative spontaneous volume magnetostriction; $\ensuremath{\omega}=\ensuremath{-}300$ ppm at 190K. Neutron powder diffraction studies of the magnetic ground state reveal an evolution in complexity as temperature decreases: from a ferromagnet, to a canted antiferromagnet, to the eventual formation of a spin-density-wave state at low temperatures.

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.

The complete 31P NMR chemical shift tensors for 22 inorganic phosphates obtained from ab initio computation are found to correspond closely to experimentally obtained parameters. Further improvement was found when structures determined by diffraction were geometry optimized. Besides aiding in spectral assignment, the cases where correspondence is significantly improved upon geometry optimization point to the crystal structures requiring correction.