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<p>Ternary actinide compounds allow for a range of oxidation states and a rich but often not well-known chemistry. Here, a BaO-deficient plutonium-containing perovskite with a composition close to Ba<sub>3</sub>PuO<sub>6</sub> has been obtained via solid state synthesis. The compound was characterised using X-Ray Diffraction from room temperature up to 1473 K, revealing two phase transitions and ordered Ba-deficiency. X-ray Absorption Spectroscopy was performed at the Pu <i>L</i><sub>3</sub>- and <i>M</i><sub>5</sub>-edges. The XANES spectrum at the Pu <i>L</i><sub>3</sub>-edge and the XANES in high-energy resolution mode at the Pu <i>M</i><sub>5</sub>-edge both indicate a Pu(VI) oxidation state. Despite the rather complex crystallographic unit cell, Extended X-ray Absorption Fine Structure (EXAFS) spectroscopy at the Pu <i>L</i><sub>3</sub>-edge yields Pu-O distances of 2.01(1) and 2.4(3) Å. The low-temperature heat capacity of Ba<sub>2.875</sub>PuO<sub>5.875</sub> was measured between 5 and 270 K. The heat capacity and standard entropy at 298.15 K were found to be <i>C</i><sub><i>p</i></sub> =&#xa0;(251&#xa0;±&#xa0;8)&#xa0;J⋅K<sup>−1</sup>⋅mol<sup>−1</sup> and <InlineEquation ID="IEq1"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="42004_2025_1669_Article_IEq1.gif" Format="GIF" Height="21" Rendition="HTML" Resolution="72" Type="Linedraw" Width="208" /> </InlineMediaObject> <EquationSource Format="TEX">\({S}_{m}^{0}=(318\pm 8)\,{{\rm{J}}} \! \cdot \! {{{\rm{K}}}}^{-1} \cdot {{{\rm{mol}}}}^{-1}\)</EquationSource> <EquationSource Format="MATHML"><math> <msubsup> <mrow> <mi>S</mi> </mrow> <mrow> <mi>m</mi> </mrow> <mrow> <mn>0</mn> </mrow> </msubsup> <mo>=</mo> <mrow> <mo>(</mo> <mrow> <mn>318</mn> <mo>±</mo> <mn>8</mn> </mrow> <mo>)</mo> </mrow> <mspace width="0.25em" /> <mi mathvariant="normal">J</mi> <mspace width="0.3em" /> <mo>⋅</mo> <mspace width="0.3em" /> <msup> <mrow> <mi mathvariant="normal">K</mi> </mrow> <mrow> <mo>−</mo> <mn>1</mn> </mrow> </msup> <mo>⋅</mo> <msup> <mrow> <mi mathvariant="normal">mol</mi> </mrow> <mrow> <mo>−</mo> <mn>1</mn> </mrow> </msup> </math></EquationSource> </InlineEquation>, respectively. The magnetic susceptibility was measured from 2 to 320 K and shows a temperature-independent paramagnetism, consistent with the hexavalent oxidation state of Pu. This article reports the first extended low-temperature heat capacity curve and a temperature-dependent magnetic susceptibility measurement in a [Rn]5<i>f</i><sup>2</sup> Pu-based system.</p>

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Structural and physical investigation of ordered BaO-deficient Ba3PuO6

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2025年9月1日

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  • Andries van Hattem,
  • Karin Popa,
  • Gilles Wallez,
  • Jacobus Boshoven,
  • Eric Colineau,
  • Eckhard Dahms,
  • Jean-Christophe Griveau,
  • Herwin Hein,
  • Olaf Walter,
  • Bianca Schacherl,
  • Tonya Vitova,
  • Kathy Dardenne,
  • Tim Pruessmann,
  • Jörg Rothe,
  • Anna L. Smith,
  • Rudy J. M. Konings

摘要

Ternary actinide compounds allow for a range of oxidation states and a rich but often not well-known chemistry. Here, a BaO-deficient plutonium-containing perovskite with a composition close to Ba3PuO6 has been obtained via solid state synthesis. The compound was characterised using X-Ray Diffraction from room temperature up to 1473 K, revealing two phase transitions and ordered Ba-deficiency. X-ray Absorption Spectroscopy was performed at the Pu L3- and M5-edges. The XANES spectrum at the Pu L3-edge and the XANES in high-energy resolution mode at the Pu M5-edge both indicate a Pu(VI) oxidation state. Despite the rather complex crystallographic unit cell, Extended X-ray Absorption Fine Structure (EXAFS) spectroscopy at the Pu L3-edge yields Pu-O distances of 2.01(1) and 2.4(3) Å. The low-temperature heat capacity of Ba2.875PuO5.875 was measured between 5 and 270 K. The heat capacity and standard entropy at 298.15 K were found to be Cp = (251 ± 8) J⋅K−1⋅mol−1 and \({S}_{m}^{0}=(318\pm 8)\,{{\rm{J}}} \! \cdot \! {{{\rm{K}}}}^{-1} \cdot {{{\rm{mol}}}}^{-1}\) S m 0 = ( 318 ± 8 ) J ⋅ K − 1 ⋅ mol − 1 , respectively. The magnetic susceptibility was measured from 2 to 320 K and shows a temperature-independent paramagnetism, consistent with the hexavalent oxidation state of Pu. This article reports the first extended low-temperature heat capacity curve and a temperature-dependent magnetic susceptibility measurement in a [Rn]5f2 Pu-based system.