X-ray structural study of layered compounds CoxTiS2

Graduate School of Pure and Applied Sciences, University of Tsukuba* National Institute of Advanced Industrial Science and Technology(AIST)**
○Takeshi Osakabe* Yasuhiko Takahashi** Takuro Kawasaki* Ken-ichi Ohshima*

The transition metal dichalcogenides and their intercalation compounds have layered type structures and are regarded as two-dimensional solids. They have been studied due to their interesting physical and chemical properties and their potential applications. It is important to understand the relationship between the structure and the properties. It is peculiar that the c-axis lattice spacing in CoxTiS2 is decreasing with increasing the Co content. We have, therefore, performed X-ray structural determinations for the single clystals of CoxTiS2(x=1/4, 1/3), which were grown by the chemical vaper transport method using iodine as a transport gas.
The X-ray intensity data were collected with the use of four circle diffractmeter AFC7(Rigaku) at room temperature.
Space groups of CoxTiS2(x=1/4, 1/3) are P-3m1(164) and P-31c(163) of the trigonal system, respectively. Co atoms have two kinds of ordered structure depending on their composition. The cell constants a=7.148, b=7.148, c=11.88Å(x=1/4), a=5.8798, b=5.8798, c=11.2579Å(x=1/3) were refined.
Co atoms occupy the octahedral sites in the van der Waals gap. As the Co composition increases, the van der Waals gap layer becomes narrow. The results of maximum entropy method analysis show the covalent bonding between Ti and S atoms, and between Co and S atoms.