Resolving the pressure induced 'self-insertion' in skutterudite CoSb3

/ Authors

Bihan Wang, A. Pakhomova, S. Khandarkhaeva, M. Pillaca, Peter Gille, Zhe Ren, D. Lapkin, D. Assalauova, Pavel Alexeev, Ilya Sergeev

and 6 more authors

Satishkumar Kulkarni, Tsu-Chien Weng, M. Sprung, H. Liermann, I. Vartanyants, Konstantin Glazyrin

/ Abstract

CoSb3, a skutterudite compound, is key in studying thermoelectric materials. Under compression, it undergoes a 'self-insertion' isostructural transition, redistributing large Sb atoms among crystallographic sites. We investigated CoSb3's structural stability up to 70 GPa using single crystal X-ray diffraction and high-resolution X-ray scattering, including Bragg Coherent Diffraction Imaging. We examined the material in three pressure transmitting media (PTMs), exploring how PTMs and nonhydrostatic stresses affect CoSb3. Notably, the 'self-insertion' transition may reduce or even make compressibility negative. Additionally, we report a previously unknown phase transformation from cubic Im-3 to trigonal R-3 above 40 GPa and discuss the phases' distinctive behaviors.