In this work, high pressure was used as a tool to induce structural transition and prepare metastable polymorphs of ternary sulfides. Structural transformations under high pressure of compounds belonging to the Ba 2 Co 1-x Zn x S 3 (0 ≤ x ≤ 1.0) series were studied using X-ray diffraction and electron microscopy. All members of the Ba 2 Co 1-x Zn x S 3 series show the Ba 2 CoS 3 -type one-dimensional structure, but, after heating under pressure, the Ba 2 CoS 3 compound (x = 0) separates into BaS and the two-dimensional BaCoS 2-δ (δ ≈ 0), while Ba 2 Co 1-x Zn x S 3 compounds with x ≥ 0.25 maintain their one-dimensional features but rearrange into polymorphs showing the Ba 2 MnS 3 -type structure. All structural transformations can be linked to shortening in interchain metal-metal distances caused by the high pressure, and the role of the zinc in preventing loss of one-dimensionality is discussed. © 2011 …