High-throughput phase exploration of ternary transition metal carbide TM-X-C (X=Al/Si) thin films
S. Richter, C. Gutschka, D. A. Danner, Rainer Hahn, Tomasz Wójcik, Eleni Ntemou, Carmen Jerg, J. Ramm, P. Polcik, S. Kolozsvári, Daniel Primetzhofer, H. Riedl
Abstract
Transition metal carbides (TMCs) are highly valued for their exceptional thermal stability (melting temperatures up to 4000 °C), refractory character, and outstanding mechanical properties, particularly hardness. These properties make TMCs crucial for applications in extreme conditions, such as in aerospace and tooling industries. Striving for novel oxidation-resistant ternary carbides, we systematically screened the phase formation of TM-X-C (where X = Al or Si) using a combined theoretical and experimental high-throughput approach. Density functional theory (DFT) calculations forecast the phase formation of (meta)stable TM-X-C solid solutions (with TM = Ti, Zr, Hf, Ta, W) using the formation energy and lattice constant ratios as structural key parameters. These theoretical predictions are experimentally validated by synthesizing over 260 compositions across the 10 different TM-X-C material systems by combinatorial magnetron sputtering. The DFT calculations indicated that Si preferentially occupies both C and TM sites, while Al tends to fill TM sites. Structural analysis experimentally confirmed the formation of face-centered-cubic TM-X-C solid solutions up to alloying contents of 25–30 at.% – for all material families except W-X-C. Additional TEM investigation confirmed the formation of fcc solid solutions. A strong correlation between prevalent phases and mechanical properties is observed, with the highest hardness values (30–40 GPa) found for fcc structured TM-X-C thin films, followed by a significant decrease entering multi-phased or amorphization phase regions – typically occurring above 25 at.% Al or Si. This comprehensive phase screening paves the way for a targeted development of novel TM-X-C ceramic thin film materials.