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 Badeficiency. 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 S0 m ¼ ð318 ± 8Þ 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]5f 2 Pu-based system.

ANDRIES Van Hattem;  POPA Karin;  WALLEZ G;  BOSHOVEN Co;  COLINEAU Eric;  DAHMS Eckhard;  GRIVEAU Jean-Christophe;  HEIN Herwin;  WALTER Olaf;  SCHACHERL Bianca;  VITOVA T.;  DARDENNE K.;  PRUESSMANN Tim;  ROTHE Jorg;  SMITH Anna;  KONINGS Rudy; 

2025-09-03

NATURE PORTFOLIO

JRC141765

2399-3669 (online),   

https://link.springer.com/article/10.1038/s42004-025-01669-x,    https://publications.jrc.ec.europa.eu/repository/handle/JRC141765,   

10.1038/s42004-025-01669-x (online),