Plutonium_borides Knowpia

Several plutonium borides can be formed by direct combination of plutonium and boron powders in an inert atmosphere at reduced pressure.

Structure of PuB₂: boron atoms shown red in hexagonally bonded network; metal atoms shown green in interleaving layers

Structure of PuB₆ (boron atoms in octahedral groups shown red with plutonium atoms shown blue at cubical vertices; bonding depiction is naïve)

PuB was reported to form at 1200 °C with a range of 40–70% boron. It supposedly has a Pu-B bond length of 2.46 Å and the NaCl structure, as do TiB, ZrB and HfB.^[1] The existence of PuB was contested later based on several arguments.^[2]

PuB₂ is formed at 800 °C and has a similar structure to most other metal diborides.

At 1200 °C with 70–85% boron, mixtures of PuB₄ and PuB₆ are formed, with more of the latter as the temperature increases; PuB₄ has the tetragonal structure (same as UB₄), and PuB₆ has cubic structure, same as all hexaborides (CaB₆, LaB₆ etc.).^[1]

The most remarkable plutonium boride is arguably PuB₁₀₀. Its existence^[2] demonstrates the importance of contamination in boride research because as little as 1% of an impurity is capable of changing its crystal structure.

References edit

^ ^a ^b B. J. McDonald; W. I. Stuart (1960). "The crystal structures of some plutonium borides". Acta Crystallogr. 13 (5): 447–448. doi:10.1107/S0365110X60001059.
^ ^a ^b H. A. Eick (1965). "Plutonium Borides". Inorganic Chemistry. 4 (8): 1237–1239. doi:10.1021/ic50030a037.

[a1960-1] B. J. McDonald; W. I. Stuart (1960). "The crystal structures of some plutonium borides". Acta Crystallogr. 13 (5): 447–448. doi:10.1107/S0365110X60001059.

[a1965-2] H. A. Eick (1965). "Plutonium Borides". Inorganic Chemistry. 4 (8): 1237–1239. doi:10.1021/ic50030a037.

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Summary

References edit