ELECTRICAL AND STRUCTURAL PROPERTIES OF SOME TERNARY CHALCOGENIDES OF TITANIUM

Electrical resistivity and Seebeck coefficient measurements have shown the six compounds MTi2X4(M = Fe,Co,Ni; X = S,Se) to exhibit metallic behavior. This is accounted for on the basis of direct Ti-Ti overlap. At room temperature, these compounds all have the monoclinic Cr3S4-type structure (space group 12/m), which is characterized by ordered vacancies in alternate metal layers. A reversible temperature-dependent transformation to a disordered trigonal structure (space group P3ml) has been shown to occur for NiTi2S4 and NiTi2Se4 at approximately 340°K. The resistivity plots for both compounds show an increase in the resistivity at approximately the same temperature. This change in resistivity is a result of the disordering of the vacancies in the structure. © 1968.