Stabilization of HfB12 in Y1–xHfxB12 under Ambient Pressure

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• 作者：Georgiy Akopov ; Michael T. Yeung ; Christopher L. Turner ; Rebecca L. Li ; Richard B. Kaner
• 刊名：Inorganic Chemistry
• 出版年：2016
• 出版时间：May 16, 2016
• 年：2016
• 卷：55
• 期：10
• 页码：5051-5055
• 全文大小：416K
• 年卷期：0
• ISSN：1520-510X

文摘

Alloys of metal dodecaborides—YBb>12b> with HfBb>12b>—were prepared via arc-melting in order to stabilize the metastable HfBb>12b> high-pressure phase under ambient pressure. Previously, HfBb>12b> 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 HfBb>12b> in Yb>1–xb>Hfb>xb>Bb>12b> (cubic UBb>12b> 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 YBb>12b>) to 7.454 Å across the solid solution range. Vickers hardness increased from 40.9 ± 1.6 GPa for pure YBb>12b> to 45.0 ± 1.9 GPa under an applied load of 0.49 N for the Yb>1–xb>Hfb>xb>Bb>12b> solid solution composition with ∼28 at. % Hf, suggesting both solid solution hardening and extrinsic hardening due to the formation of secondary phases of hafnium.