Olivine Crystal Structure-Directed Twinning in Iron Germanium Sulfide (Fe₂GeS₄) Nanoparticles

Abstract

Understanding the microstructure of complex crystal structures is critical for controlling material properties in next-generation devices. Synthetic reports of twinning in bulk and nanostructured crystals with detailed crystallographic characterization are integral for advancing systematic studies of twinning phenomena. Herein, we report a synthetic route to controllably twinned olivine nanoparticles. Microstructural characterization of Fe2GeS4 nanoparticles via electron microscopy (imaging, diffraction, and crystallographic analysis) demonstrates the formation of triplets of twins, or trillings. We establish synthetic control over the particle crystallinity and crystal growth. We describe the geometrical basis for twin formation, hexagonal pseudosymmetry of the orthorhombic lattice, and rank all of the reported olivine compounds according to this favorability to form twins. The work in this study highlights an area ripe for future exploration with respect to the advancement of solution-phase synthetic approaches that can control microstructure in compositionally complex, technologically relevant structures. Finally, we discuss the potential implications for olivine properties and performance in various applications.

Periodic TableTalks: An Oasis of Science within a Conference Desert

“…This route avoids the formation of unwanted iron sulfide phases, which had plagued earlier syntheses. Building on this work, Prieto and colleagues found that they could generate controllably twinned Fe 2 GeS 4 nanoparticles by altering the precursor concentrations . This remarkable control of the crystal morphology should facilitate the incorporation of Fe 2 GeS 4 nanoparticles into future photovoltaic devices.…”

“…The new class of batteries inspired by her vision and scientific advances has the potential to evolve battery technology within a sustainable manufacturing platform . The Prieto group is also developing new photovoltaics, including nanostructured iron germanium sulfide (Fe 2 GeS 4 ). , Of particular note is the innovative synthesis of Fe 2 GeS 4 nanostars using Li­(N­{Si­[CH 3 ] 3 } 2 ) as the base and S 8 as the sulfur source, which the team reported in 2020. This route avoids the formation of unwanted iron sulfide phases, which had plagued earlier syntheses.…”

Disequilibrium reaction pathways and the twin-mediated growth of tabular forsterite during contact metamorphism of quartz-bearing dolomite

“…The dihedral angle between twin members is approximately 60 ± 0 . 5 ◦ for each law (Welsch et al 2013 ; Azevedo and Nespolo 2017 ; Miller et al 2021 ), which precludes discrimination via conventional EBSD procedure. The twin laws have exactly the same twin lattice but different twin planes.…”

Versatile Fe2GeS4 for Li/Na–Fe2GeS4 battery cathodes and Li/Na-ion battery anodes

“…[43][44][45][46][47][48][49][50] Iron germanium sulde (Fe 2 GeS 4 ) is a ternary compound with an interesting olivine crystal structure consisting of S 2− in a hexagonal close-packed structure, with half of the octahedral sites occupying Fe 2+ and an eighth of the tetrahedral sites occupying Ge 4+ . 51 Ternary Fe 2 GeS 4 is a thermodynamically stable phase with a moderately high adsorption coefficient (>10 5 cm −1 ) and a suitable band gap (1.40 eV), which is ideal for various photovoltaic applications. 52,53 Large amounts of Li or Na can electrochemically alloy with Ge and S to produce a high Li or Na storage capacity, while inactive Fe can serve as a Li or Na-inactive buffer matrix to mitigate volume changes upon cycling; thus, Fe 2 GeS 4 can be employed as a high-capacity energy storage material.…”