Stabilization of HfB12 in Y1-xHfxB12 under Ambient Pressure

• Published in: Inorganic chemistry Vol. 55; no. 10; pp. 5051 - 5055
• Main Authors: Akopov, Georgiy, Yeung, Michael T, Turner, Christopher L, Li, Rebecca L, Kaner, Richard B
• Format: Journal Article
• Language: English
• Published: United States 16-05-2016
• ISSN: 1520-510X
• DOI: 10.1021/acs.inorgchem.6b00627

Alloys of metal dodecaborides-YB12 with HfB12-were prepared via arc-melting in order to stabilize the metastable HfB12 high-pressure phase under ambient pressure. Previously, HfB12 had been synthesized only under high-pressure (6.5 GPa). Powder X-ray diffraction (PXRD) and energy-dispersive X-ray spectroscopy (EDS) were used to confirm the purity and phase composition of the prepared samples. The solubility limit for HfB12 in Y1-xHfxB12 (cubic UB12 structure type) was determined to be ∼35 at. % Hf by PXRD and EDS analysis. The value of the cubic unit cell parameter (a) changed from 7.505 Å (pure YB12) to 7.454 Å across the solid solution range. Vickers hardness increased from 40.9 ± 1.6 GPa for pure YB12 to 45.0 ± 1.9 GPa under an applied load of 0.49 N for the Y1-xHfxB12 solid solution composition with ∼28 at. % Hf, suggesting both solid solution hardening and extrinsic hardening due to the formation of secondary phases of hafnium.