[Back]

A Kirnbauer, P.H. Mayrhofer:
"High-entropy ceramic thin films synthesized by magnetron sputtering";
Talk: Materials Research Society- Fall Meeting 2019 (MRS 2019), Boston, MA, USA; 2019-12-01 - 2019-12-06.

The demand on materials for various applications is growing continuously, especially in the field of ceramic coatings used to protect various components or tools for hard-to-machine materials. The development of materials that can withstand high thermal and mechanical loads is therefore in focus of many materials science activities. In this respective, a relatively new class of materials, so-called high-entropy materials, gained enormous attraction. These alloys consist of multiple principal elements (more than 5), which lead to a high configurational entropy (> 1.5R, R being the universal gas constant) if single-phased. Typically, these high-entropy materials exhibit four core effects: 1) The high-entropy effect, which significantly reduces the overall Gibbs free-energy (especially with increasing temperature); 2) the severe lattice distortion, stemming from the different atom radii forming the solid solution; 3) the sluggish diffusion, due to the increased activation energy for diffusion as the individual atomic neighbourhood is different; and 4) the so-called cocktail effect, allowing to combine the individual properties.
More recently as for metallic bulk materials, this concept was also introduced to ceramics and especially hard coatings and ceramic thin films.
Here we show the beneficial effect of the high-entropy concept applied to several thin film material systems including nitrides, borides, and oxides. The study focuses on their preparation with physical vapor deposition, their (non)sensitivity to deposition parameters, their thermal stability and mechanical properties. All coatings investigated exhibit outstanding thermal stability and significantly decelerated decomposition and softening processes, outperforming their commonly-used binary or ternary constituents.