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Abstract High entropy oxides (HEOs) have garnered much interest due to their available high degree of tunability. Here, we study the local structure of (MgNiCuCoZn)_0.167(MnCr)_0.083O, a composition based on the parent HEO (MgNiCuCoZn)_0.2O. We synthesized a series of thin films via pulsed laser deposition at incremental oxygen partial pressures. X‐ray diffraction shows lattice parameters to decrease with increased pO₂ pressures until the onset of phase separation. X‐ray absorption fine structure shows that specific atomic species in the composition dictate the global structure of the material as Cr, Co, and Mn shift to energetically favorable coordination with increasing pressure. Transmission electron microscopy analysis on a lower‐pressure sample exhibits a rock salt structure, but the higher‐pressure sample reveals reflections reminiscent of the spinel structure. In all, these findings give a more complete picture of how (MgNiCuCoZn)_0.167(MnCr)_0.083O forms with varying initial conditions and advances fundamental knowledge of cation behavior in high entropy oxides. 

Abstract Interest in high‐entropy inorganic compounds originates from their ability to stabilize cations and anions in local environments that rarely occur at standard temperature and pressure. This leads to new crystalline phases in many‐cation formulations with structures and properties that depart from conventional trends. The highest‐entropy homogeneous and random solid solution is a parent structure from which a continuum of lower‐entropy offspring can originate by adopting chemical and/or structural order. This report demonstrates how synthesis conditions, thermal history, and elastic and chemical boundary conditions conspire to regulate this process in Mg_0.2Co_0.2Ni_0.2Cu_0.2Zn_0.2O, during which coherent CuO nanotweeds and spinel nanocuboids evolve. We do so by combining structured synthesis routes, atomic‐resolution microscopy and spectroscopy, density functional theory, and a phase field modeling framework that accurately predicts the emergent structure and local chemistry. This establishes a framework to appreciate, understand, and predict the macrostate spectrum available to a high‐entropy system that is critical to rationalizing property engineering opportunities. 

Abstract Large-density functional theory (DFT) databases are a treasure trove of energies, forces, and stresses that can be used to train machine-learned interatomic potentials for atomistic modeling. Herein, we employ structural relaxations from the AFLOW database to train moment tensor potentials (MTPs) for four carbide systems: CHfTa, CHfZr, CMoW, and CTaTi. The resulting MTPs are used to relax ~6300 random symmetric structures, and are subsequently improved via active learning to generate robust potentials (RP) that can relax a wide variety of structures, and accurate potentials (AP) designed for the relaxation of low-energy systems. This protocol is shown to yield convex hulls that are indistinguishable from those predicted by AFLOW for the CHfTa, CHfZr, and CTaTi systems, and in the case of the CMoW system to predict thermodynamically stable structures that are not found within AFLOW, highlighting the potential of the employed protocol within crystal structure prediction. Relaxation of over three hundred (Mo_1−xW_x)C stoichiometry crystals first with the RP then with the AP yields formation enthalpies that are in excellent agreement with those obtained via DFT. 

Abstract We report on the structure and dielectric properties of ternary A₆B₂O₁₇(A = Zr; B = Nb, Ta) thin films and ceramics. Thin films are produced via sputter deposition from dense, phase‐homogenous bulk ceramic targets, which are synthesized through a reactive sintering process at 1500°C. Crystal structure, microstructure, chemistry, and dielectric properties are characterized by X‐ray diffraction and reflectivity, atomic force microscopy, X‐ray photoelectron spectroscopy, and capacitance analysis, respectively. We observe relative permittivities approaching 60 and loss tangents <1 × 10⁻²across the 10³–10⁵ Hz frequency range in the Zr₆Nb₂O₁₇and Zr₆Ta₂O₁₇phases. These observations create an opportunity space for this novel class of disordered oxide electroceramics. 

We report on temperature-dependent dielectric behavior of disordered ternary A6B2O17 (A = Zr, Hf; B = Nb, Ta)-form oxides in the GHz frequency range. The microwave dielectric properties including relative permittivity, dielectric loss, and temperature-dependent relative permittivity were characterized using cylindrical dielectric resonators using a resonant post measurement technique. Dielectric measurements through the resonant post method approach generally agree with dielectric measurements of A6B2O17 bulk ceramics measured through standard resonant post techniques. Coefficients describing the temperature-dependent relative permittivity for ternary A6B2O17 phases are strongly positive, suggesting contributions to polarizability arising from long-range mechanisms potentially associated with structural disorder. These observations support the working hypothesis that material functionality can be engineered by the chemical diversity and structural disorder possible in high configurational entropy A6B2O17 phases.