“…From a general point, the permittivity results from both intrinsic or extrinsic properties, the latter been associated with possible existence of domains, defects, doping, internal strains … [21][22][23]. In some cases, a strong increase in permittivity, slightly constant on a large range of temperatures can be observed depending on the doped BaTiO 3 substitution [24] or on the synthesis atmosphere which can create vacancies or doping on the grain surface but not penetrate the interior of the grains [25]. Permittivity values as high as 10 5 have been reported for nanostructured materials, such as core-shell structures with a BaTiO 3 core and a shell made of another material like SiO 2 ,Al 2 O 3 … [26].…”