Single-crystalline LaxPr1−xB6 nanoawls: Synthesis, characterization and growth mechanism

Lanthanum-praseodymium hexaboride (LaxPr1−xB6) nanoawls have been fabricated via a simple flux-controlled method using lanthanum (La) powders, praseodymium (Pr) powders and boron trichloride (BCl3) gas as starting materials at 1050 °C. Scanning electron microscopy (SEM) shows that the tapered nanoawls have a length of 2-10 μm and a diameter ranging from 50 to 300 nm at the roots and 10-80 nm at the tips. Transmission electron microscopy (TEM) reveals that the nanoawls are single crystalline with the preferred growth direction along [110]. Raman spectra indicate that the T1u mode splitting effect occurs in this ternary rare-earth hexaboride. In addition, a concentration gradient is necessary to create these awl-like structures where the combination of self-catalyzed and vapor-solid growth is responsible for the growth of tapered LaxPr1−xB6 nanoawls.