Cu x UTe3:  Stabilization of UTe3 in the ZrSe3 Structure Type via Copper Insertion. The Artifact of Te−Te Chains and Evidence for Distortions Due to Long Range Modulations

• Published in: Journal of the American Chemical Society 2001-05, Vol.123 (20), p.4755-4762
• Main Authors: Patschke, Rhonda, Breshears, Jean D, Brazis, Paul, Kannewurf, Carl R, Billinge, Simon J. L, Kanatzidis, Mercouri G
• Format: Article
• Language: English
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/ja0042534

The ternary phase, Cu x UTe3 (x = 0.25 and 0.33), was synthesized from a 3/1/4 mixture of Cu/U/Te that was heated to 800 °C for 6 days and cooled at a rate of −4 °C h-1. It adopts the monoclinic space group P21/m with a = 6.0838(12) Å, b = 4.2140(8) Å, c = 10.361(2) Å, β = 98.83(3)°, and V = 262.47(9) Å3 (for x ∼ 0.25). The structure is built from UTe3 layers of ZrSe3-type that are connected in the [001] direction by Cu atoms. The Cu atoms stabilize α-UTe3 by inserting between the layers. Cu x UTe3 can be prepared rationally via a soft chemistry route by reaction of Cu with α-UTe3. The structural analysis suggests the presence of straight chains of Te atoms (∼3.0 Å apart) along the a-axis but this is an artifact as shown by electron diffraction studies of Cu x UTe3 that indicate the existence of a supercell along the a-axis. Pair distribution function analysis (PDF) was used to show that the Te−Te chains contain Te−Te dimers at 2.74 Å. Charge transport measurements suggest a narrow gap semiconductor but they also indicate anomalous behavior as a function of temperature with a n-type to p-type transition at ∼40 K.