Structural, optical, electrical and phase separation properties and their relationship to composition in CdTe-Sb co-sputtered thin films have been studied. Ternary compounds were grown on glass substrates by co-sputtering of Sb and CdTe. The substrate temperature was varied from room temperature to 250 degrees C. The composition measurements show that the average Sb content in the layers is in the range from 8 to 60 at.%, depending on the area fraction covered by the Sb metallic piece added onto the CdTe target. The Sb content is found to be independent of the substrate temperature. The structure of the films was determined from X-ray diffraction measurements. Three kinds of structures were observed, depending on Sb content and substrate temperature. A three-dimensional image sequence, measured by atomic force microscopy, shows the surface roughness behavior of the samples as a function of the Sb content at room temperature. The introduction of Sb in the samples grown at room temperature produces deep level centers as shown by near-infrared absorption measurements.