X-ray Diffraction, Topographical Studies, and Thermal Behavior of Layer-Type CdIn₂S₄₋xSex (1.75 ≤ x ≤ 2.75) and Its Lithium Intercalation Compounds

The present paper deals with the preparation of ZnIn 2 S 4 −IIIa layer-type CdIn 2 S 4 - x Se x (1.75≤ x ≤ 2.75) quaternary chalcogenides and their characterization. X-ray diffraction studies of CdIn 2 S 4 - x Se x (1.75 ≤ x ≤ 2.75) confirmed that all of these compounds possess the ZnIn 2 S 4 −IIIa type of structure. The variation of the composition x shows that both lattice parameters a- and c increase with a growing amount of selenium in the crystals. The calculation of microstructural parameters by an X-ray line profile analysis has shown that the intercalation of lithium in the host CdIn 2 S 2 Se 2 is accompanied by a decrease in crystallite size while the dislocation density and the rms strain are increasing. The process of intercalation results in no expansion along the c -axis, probably due to no increase in the c -parameter at all in a given intercalation process; which does not have purely geometric origin but also comes from electronic effects. A radial distribution function (RDF) analysis of these quaternary chalcogenides indicated the presence of peaks at ∼2.5 and 4.5 Å metal−chalcogen and metal−metal distances, respectively. The peaks above 6 Å are due to the higher order metal−chalcogen and chalcogen−chalcogen distances. The apparent crystallite size of CdIn 2 S 4 - x Se x (1.75 ≤ x ≤ 2.75) compounds deduced from X-ray studies has been correlated with the scanning electron micrographs. Scanning tunneling microscopic studies revealed that the surface of the CdIn 2 S 2 Se 2 crystals is not smooth. All of the compounds are thermally stable up to about 450 °C in air atmosphere.