Issue 17, 2024

BaCuTP2 (T = Al, Ga, In): a semiconducting black sheep in the ThCr2Si2 intermetallic family

Abstract

The ThCr2Si2 structure type has been well explored for decades with diverse magnetic, superconducting, and heavy-fermion behavior. For transition metal-containing ThCr2Si2-type compounds, a metallic band structure and properties are typical. In this work, a rare example of semiconducting BaCuTP2 (T = Al, Ga, In) materials is reported. BaCuTP2 materials retain the tetragonal I4/mmm ThCr2Si2-type crystal structure with a large c/a ratio of ∼3.3, where Cu and T metals jointly occupy the Cr-site. Edge-sharing (Cu/T)P4 tetrahedra form [CuTP2]2− layers stacked along the crystallographic [001] direction, with the Ba2+ cations located in the interlayer spaces. Solid state NMR revealed partial short-range ordering in the Cu/T sublattice. The composition of the produced phases is electron balanced, Ba2+Cu1+T3+(P3−)2. High values of Seebeck coefficients were experimentally observed due to the high valley degeneracy in the band structure. Heat capacity and structural studies show that Ba exhibits anisotropic ‘rattling-like’ behavior along the [001] direction in Ga- and In-containing compounds. A combination of Ba rattling, short range Cu/T ordering, and a recently discovered coupling between acoustic and optical phonons for ThCr2Si2-type phosphides, resulted in ultralow thermal conductivity (<0.50 W m−1 K−1) for the title compounds.

Graphical abstract: BaCuTP2 (T = Al, Ga, In): a semiconducting black sheep in the ThCr2Si2 intermetallic family

Supplementary files

Article information

Article type
Paper
Submitted
15 Feb 2024
Accepted
15 Mar 2024
First published
15 Mar 2024
This article is Open Access
Creative Commons BY-NC license

J. Mater. Chem. A, 2024,12, 10481-10493

BaCuTP2 (T = Al, Ga, In): a semiconducting black sheep in the ThCr2Si2 intermetallic family

A. Sarkar, A. P. Porter, G. Viswanathan, P. Yox, R. A. Earnest, J. Wang, A. J. Rossini and K. Kovnir, J. Mater. Chem. A, 2024, 12, 10481 DOI: 10.1039/D4TA01063A

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