Alloy-Assisted Formation of Vanadium-Rich Thiophosphates with Enhanced Charge Transport and Glassy Magnetism

Abstract

Vanadium-based thiophosphates in the MPQ3/M2P2Q6 family provide an unusual platform for coupling mixed-metal valence, metal vacancies, and 2D magnetism, but access to phase-pure multimetal solid solutions with verified chemical homogeneity remains limited. Here, we show that multication alloying provides a route to incorporating V into layered thiophosphates while retaining the mixed-valent, vacancy-containing character of V2−xP2S6. This approach yields Fe1.25V0.6P2S6, Ni1.25V0.6P2S6, Co1.25V0.6P2S6, and high-entropy V-containing compositions. Single-crystal X-ray diffraction (scXRD) and electron energy-loss spectroscopy (EELS) mapping confirm formation of layered single-phase alloys and chemical uniformity both across the surface and through the flake thickness. Optical measurements show semiconducting band gaps spanning ∼1.33−1.66 eV, while temperature-dependent transport reveals markedly enhanced conductivity and low activation energies (∼0.2−0.3 eV) relative to conventional divalent TM2P2S6 analogs. Oxidation-state mapping indicates robust mixed-valent V2+/V3+ character consistent with defect-assisted hopping and self-doping linked to vanadium vacancies, likely causing enhanced conductivity. Magnetic measurements further show composition-dependent behavior, consistent with magnetic frustration and glassy components in Fe1.25V0.6P2S6 and (VMnFeCoNi)2P2S6, highlighting the role of multimetal disorder in shaping exchange interactions. Together, these results establish a route to phase-pure, conductive V-containing thiophosphate alloys and expand the tunable design space for coupled transport and magnetism in layered chalcophosphates.