Pressureless spark plasma sintering: A new one-step route to (Cr, Mo, W)Te2 synthesis

Abstract

Transition metal ditellurides (CrTe₂, MoTe₂, WTe₂) are promising materials for spintronics and phase-change electronics. However, their synthesis by conventional methods is challenging. The process is time-consuming and often yields non-stoichiometric products due to the high volatility of tellurium. Herein, we report a single-stage, ultrafast synthesis of these compounds via a novel Pressureless Reactive Spark Plasma Sintering (PRSPS) method. We first demonstrate that the standard reactive SPS approach, even under minimal pressure (5 MPa), is unsuitable for systems with low-melting-point components, as it causes the extrusion of molten tellurium from the reaction zone. To overcome this, a bespoke, quasi-sealed die assembly was engineered and successfully implemented, isolating the reactants from external pressure and preventing material loss. Using this pressureless method, phase-pure and highly crystalline powders of CrTe₂, MoTe₂, and WTe₂ were successfully synthesized in a record time of just 15 min. Comprehensive characterization by XRD, SEM, and EDS confirmed their phase purity, stoichiometric composition (M:Te ≈ 1:2), and microcrystalline plate-like morphology. This method represents a paradigm shift in chalcogenide synthesis, reducing process times from days to minutes and providing a scalable route to high-quality powders.