Structures and Phase Transitions of CePd_3+xGa_8-x: New Variants of the BaHg₁₁ Structure Type

Abstract

New distorted variants of the cubic BaHg11 structure type have been synthesized in Ga flux. Multiple phases of CePd3+xGa8-x, which include an orthorhombic Pmmn structure (x = 3.21(2)), a rhombohedral R3m structure (x = 3.13(4)), and a cubic Fm3m superstructure (x = 2.69(6)), form preferentially depending on reaction cooling rate and isolation temperature. Differential thermal analysis and in situ temperature-dependent powder X-ray diffraction patterns show a reversible phase transition at approximately 640 °C between the low temperature orthorhombic and rhombohedral structures and the high temperature cubic superstructure. Single crystal X-ray diffraction experiments indicate that the general structure of BaHg11, including the intersecting planes of a kagomé-type arrangement of Ce atoms, is only slightly distorted in the low temperature phases. A combination of Kondo, crystal electric field, and magnetic frustration effects may be present, resulting in low temperature anomalies in magnetic susceptibility, electrical resistivity, and heat capacity measurements. In addition to CePd3+xGa8-x, the rare earth analogues REPd3+xGa8-x, RE = La, Nd, Sm, Tm, and Yb, were successfully synthesized and also crystallize in one of the lower symmetry space groups.

Intermetallic Reactivity: Ca3Cu7.8Al26.2 and the Role of Electronegativity in the Stabilization of Modular Structures

“…The high-temperature polymorph of CaAl 4 is one member of a large family of BaAl 4 -type binary structures formed in many combinations of electropositive metals (alkali, alkaline earth, and lanthanide) with group 13 metals (Al, Ga, and In). − This framework serves as a parent structure to a variety of superstructures, distortions, and colored derivatives across an even broader array of elements. − The BaAl 4 -type framework thus seems to be quite structurally responsive to perturbations in the electron count, atomic size, and composition . An analysis of how these factors underlie the structure of CaAl 4 can then help us understand its evolution with the addition of another compositional dimension as we move into the ternary space of the Ca–Cu–Al system.…”

Synthesis, Structure, and Complex Magnetism of MIr2In8 (M = Eu, Sr)

“…Intermetallic compounds that contain rare-earth elements with two stable oxidation states (specifically Ce, Eu, Sm, and Yb) exhibit a wide variety of interesting and unusual physical properties including superconductivity, , heavy fermion behavior, the Kondo effect, − and non-Fermi liquid behavior . Of particular interest for our investigation of the Eu–Ir–In system are the so-called heavy fermion materials, intermetallics that exhibit carrier effective masses ( m *) far larger than can be explained by the weakly interacting electron models that describe typical metals.…”

The crystal structure and magnetic properties of a Zintl phase EuIrIn4: the first member of the Eu–Ir–In family

“…The increase in RE-RE distance decreases direct spin coupling between two adjacent atoms and they couple through the itinerant or conduction electrons giving rise to the RKKY interaction. 16,17 Motivated by our earlier work on EuAuIn 4 , we initially focused on the synthesis of EuIrIn 4 and EuPtIn 4 . During the progress of our work, we noted that two research groups also worked on EuPtIn 4 .…”