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

Lanthanum–praseodymium hexaboride (La_xPr_1?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 T_1u 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 La_xPr_1?xB₆ nanoawls.