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oai:figshare.com:article/34037486 2026-10-01T01:05:29Z category_146 category_7 category_873 category_46 category_734 category_62 category_135 portal_63 item_type_6 month_year_10_2026

Quasi-Isostructural Solid-Solution Formation of Cu₄TiSe₄ with Cu₃TMQ₄ (TM: V, Nb, Ta; Q: S, Se): Tuning “Stuffing” Concentration for Ultralow Thermal Conductivity Arnab Dutta (1872166) Achintya Lakshan (14334571) Jürgen Nuss (2022172) Partha Pratim Jana (14334577) Space Science Medicine Chemical Sciences not elsewhere classified Immunology Biological Sciences not elsewhere classified Marine Biology Computational Biology ray diffraction studies overall charge neutrality materials highly attractive low thermal conductivity 4 ̅ 3 5 +</ sup ultralow thermal conductivity >) without affecting 4 +</ sup sup >+</ sup cubic unit cell solution formation leads substituted solid solutions 3 </ sub allows additional cu 4 </ sub solution formation >< sup ultralow regime additional “< >) inside p </ interstitial </ e </ b </ solution phases tm </ tmq </ type compounds systems crystallize substantial reduction space group In this study, we adopted a quasi-isostructural solid-solution strategy involving selenotitanate Cu₄TiSe₄ and sulvanite-type Cu₃<i>TMQ</i>₄ (<i>TM</i>: V, Nb, Ta; <i>Q</i>: S, Se). At room temperature, both systems crystallize in the cubic <i>P</i>4̅3<i>m</i> space group, where Cu₄TiSe₄ additionally contains positionally disordered Cu⁺ cations occupying two Wyckoff sites (1<i>b</i> and 4<i>e</i>) inside the sulvanite framework. The crystal structures of the solid-solution phases were determined by X-ray diffraction studies. Substituting Ti⁴⁺ for <i>TM</i>⁵⁺ in Cu₃<i>TMQ</i>₄ allows additional Cu⁺ to dissolve, maintaining the overall charge neutrality. The additional “<i>interstitial</i>” Cu⁺ ions occupy positionally disordered sites (1<i>b</i> and 4<i>e</i>) without affecting the three-dimensional (3D) sulvanite frameworks, with their occupancy controlled by the Ti⁴⁺/<i>TM</i>⁵⁺ ratio. Moreover, an ordering tendency of the interstitial Cu⁺ ions is observed within the cubic unit cell of the S-substituted solid solutions. This solid-solution formation leads to a substantial reduction in effective thermal conductivity relative to the parent sulvanite-type compounds, reaching the ultralow regime, while the optical band gaps vary systematically between 0.9 and 2.62 eV. The combination of this low thermal conductivity and tunable optical bandgap makes these materials highly attractive for diverse applications. 2026-09-30T00:00:00Z Text Journal contribution 10.1021/acs.inorgchem.6c03738.s001 https://figshare.com/articles/journal_contribution/Quasi-Isostructural_Solid-Solution_Formation_of_Cu_sub_4_sub_TiSe_sub_4_sub_with_Cu_sub_3_sub_TMQ_sub_4_sub_TM_V_Nb_Ta_Q_S_Se_Tuning_Stuffing_Concentration_for_Ultralow_Thermal_Conductivity/34037486 CC BY-NC 4.0