Morphology Control of Tantalum Carbide Nanoparticles through Dopant Additions

The control of powder morphology in metals and ceramics is of critical importance in applications such as catalysis and chemical sensing whereby specific crystal facets better facilitate chemical reactions. In response to this challenge, we present a combined experimental and computational approach that examines the principles behind dopant-induced crystallographic faceting in nanoparticles. We base our study on nanoparticles of tantalum carbide doped with nickel, iron, cobalt, niobium, and titanium and observe a very significant transition from round/irregular particle shapes to cubes and cuboctahedrons upon the addition of transition metal dopants. The presence of the dopants, which segregate toward the surface of the particles, results in atomic orbital hybridization, causing a significant decrease of up to 0.13 eV·Å–2 in the surface energy of the (100) facets, thus providing the driving force for the formation of nanocubes with exposed (100) surfaces. These principles can be generalized to other ceramics and serve as guidance for the optimized control of shape in powders. For example, if one seeks to produce highly faceted V-, Hf-, or Zr-carbide nanoparticles, doping strategies reported here can be applied. Other elements may also be effective in changing the growth habits of crystals based on surface segregation and dopant–host atomic orbital hybridization.