arXiv subjects

R. Jackson Spurling

Publications and source records attributed to R. Jackson Spurling.

3 recordsLinked to original sources

arXiv2025

Automated Materials Discovery Platform Realized: Scanning Probe Microscopy of Combinatorial Libraries

Combinatorial materials libraries provide a powerful platform for mapping how physical properties evolve across binary and ternary cross-sections of multicomponent phase diagrams. While synthesis of such libraries has advanced since the 1960s and been accelerated by laboratory automation, their broader utility depends on rapid, quantitative measurements of composition-dependent structures and functionalities. Scanning probe microscopies (SPM), including piezoresponse force microscopy (PFM), offer unique potential for providing these functionally relevant, spatially resolved readouts. Here, we demonstrate a fully automated SPM framework for exploring ferroelectric properties across combinatorial libraries, focusing on binary Sm-doped BiFeO3 (SmBFO) and ternary Al$_{1-x-y}$Sc$_x$B$_y$N (Al,Sc,B)N systems. In SmBFO, automated exploration identifies the known morphotropic phase boundary with enhanced ferroelectric response and reveals a previously unreported double-peak fine structure. In the (Al,Sc,B)N library, ferroelectric behavior emerges at the phase-stability boundary, correlating with variations in morphology and defect concentration. By integrating automated SPM with wavelength-dispersive spectroscopy (WDS) and photoluminescence mapping, we resolve the composition-morphology-defect-property relationships underlying ferroelectric response and demonstrate a pathway toward a multi-tool, high-throughput characterization platform. Finally, we implement Gaussian-process-based single- and multi-objective Bayesian optimization to enable autonomous exploration, highlighting the Pareto front as a powerful framework for balancing competing physical rewards and accelerating data-driven physics discovery.

cond-mat.mtrl-sci↗

arXiv2025

Exploring Cation Selection and Disorder within Entropy-Driven $A_{6}B_{2}$O$_{17}$ ($A$=Zr/Hf, $B$=Nb/Ta) Oxides

We investigate the local atomic and electronic structure, thermodynamic stability, and defect chemistry of $A_{6}B_{2}$O$_{17}$ ($A$ = Zr/Hf, $B$ = Nb/Ta) oxides using first-principles density functional theory (DFT) calculations. We examine both ordered unit cells as well as fully disordered special quasirandom structures to clearly discern the effects of cation disorder. Structural predictions align closely with previous experimental results and follow established ionic radii trends. The electronic structure is strongly dependent on $B$-cation species: $A_{6}$Ta$_{2}$O$_{17}$ compositions have ~30% larger band gaps than their $A_{6}$Nb$_{2}$O$_{17}$ counterparts. Defect chemistry is similar for all compositions, with anion vacancies being more energetically favorable than corresponding cation defects. All explored $A_{6}B_{2}$O$_{17}$ compositions are enthalpically unstable with respect to their $A$O$_{2}$ and $B_{2}$O$_{5}$ competing oxides and are therefore classified as entropy-stabilized materials, supporting prior experimental results. The pronounced agreement between our disordered supercell predictions with experimental measurements indicates all explored $A_{6}B_{2}$O$_{17}$ compositions contain substantial cation disorder across all 6-, 7-, and 8-coordinated sites. Our findings collectively provide a fundamental understanding of the $A_{6}B_{2}$O$_{17}$ material family through DFT calculations, establishing a framework for future compositional tuning to engineer targeted material properties.

cond-mat.mtrl-sci↗

arXiv2024

Dielectric Properties of Disordered A6B2O17 (A = Zr; B = Nb, Ta) Phases

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 < 10^-2 across the 10^3-10^5 Hz frequency range in the Zr6Nb2O17 and Zr6Ta2O17 phases. These observations create an opportunity space for this novel class of disordered oxide electroceramics.

cond-mat.mtrl-sci↗