Disorder-driven glasslike thermal conductivity in colusite Cu₂₆V₂Sn₆S₃₂ investigated by Mössbauer spectroscopy and inelastic neutron scattering

Christophe Candolfi (1) , Gabin Guélou (2) , Cédric Bourgès (2) , Andrew Supka (3) , Rabih Al Rahal Al Orabi (3, 4) , Marco Fornari (3) , Bernard Malaman (1) , Gérard Le Caër (5) , Pierric Lemoine (6) , Vincent Hardy (2) , Jean-Marc Zanotti (7) , Raju Chetty (8, 9) , Michihiro Ohta (9, 8) , Koichiro Suekuni (10) , Emmanuel Guilmeau (2)

1 IJL - Institut Jean Lamour
2 CRISMAT - Laboratoire de cristallographie et sciences des matériaux
3 CMU - Central Michigan University
4 Solvay (France)
5 IPR - Institut de Physique de Rennes
6 ISCR - Institut des Sciences Chimiques de Rennes
7 MMB - LLB - Matière molle et biophysique
8 Université de Tsukuba = University of Tsukuba
9 AIST - National Institute of Advanced Industrial Science and Technology
10 Kyushu University

The influence of structural disorder on the thermal transport in the colusite Cu₂₆V₂Sn₆S₃₂ has been investigated by means of low-temperature thermal conductivity and specific heat measurements (2–300 K), ¹¹⁹Sn Mössbauer spectroscopy and temperature-dependent powder inelastic neutron scattering (INS). Variations in the high-temperature synthesis conditions act as a key parameter for tuning the degree of disorder in colusite compounds. Intriguingly, we find that all synthesized samples are disordered, the degree of which varies with the synthesis conditions used. Mössbauer data clearly evidence that Sn atoms do not solely occupy the 6c site of the crystal lattice but are present on possibly both the Cu and V sites, leading to a random distribution of these three cations within the unit cell. Increasing the disorder in these materials tends to lead to a smearing out of the main features in the phonon density of states measured by INS. Although the evolution of the inelastic signal upon warming is well described by a quasiharmonic approximation, elastic properties calculations indicate large average Grüneisen parameters, consistent with those determined experimentally from thermodynamic data. Increasing the level of disorder results in a decreased average Grüneisen parameter suggesting that the lowered lattice thermal conductivity is not driven by enhanced anharmonicity. These results provide experimental evidence to support that the remarkable changeover in the lattice thermal conductivity from crystalline to glasslike is solely driven by enhanced disorder accompanied by local lattice distortions.

Mots clés: Thermal properties; Polycrystalline materials; Mössbauer spectroscopy; Time-of-flight neutron spectroscopy

Domaines: Matériaux; Science des matériaux [cond-mat.mtrl-sci]

Christophe Candolfi, Gabin Guélou, Cédric Bourgès, Andrew Supka, Rabih Al Rahal Al Orabi, et al.. Disorder-driven glasslike thermal conductivity in colusite Cu₂₆V₂Sn₆S₃₂ investigated by Mössbauer spectroscopy and inelastic neutron scattering. Physical Review Materials, 2020, 4 (2), pp.025404. ⟨10.1103/PhysRevMaterials.4.025404⟩. ⟨hal-02507469⟩