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 ZnIn2S4-IIIa layer-type CdIn2S4-xSex (1.75 x 2.75) quaternary chalcogenides and their characterization. X-ray diffraction studies of CdIn2S4-xSex (1.75 x 2.75) confirmed that all of these compounds possess the ZnIn2S4-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 CdIn2S2Se2 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 A metal-chalcogen and metal-metal distances, respectively. The peaks above 6 A are due to the higher order metal-chalcogen and chalcogen-chalcogen distances. The apparent crystallite size of CdIn2S4-xSex (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 CdIn2S2Se2 crystals is not smooth. All of the compounds are thermally stable up to about 450 C in air atmosphere.