Ceramic samples with the nominal composition (1-x) BaTiO3 + x Ba3Ti2YO8.5 (x = 0 - 0.4) were prepared by the solid-state reaction method. The X-ray diffraction (XRD) analysis and the lattice parameters determination indicate that the samples with x≤ 0.16 exhibit a single phase cubic perovskite structure. When x > 0.16, the system is of biphasic composites, which consist of Ba(Ti0.911Y0.089)O3 and Ba3Ti2YO8.5. The microstructure observation by Scanning Electron Microscopy (SEM) supports the XRD result. For the biphasic composites, the dielectric constant follows the Lichtenecker relation in a wide temperature range.