Dielectric evidences of core-shell-like effects in nanosized relaxor PbMg1∕3Nb2∕3O3

Temperature and frequency dependence of dielectric permittivity in nanotextured ceramics of PbMg1∕3Nb2∕3O3 has been performed in a wide range of grain sizes and shown to display strong variation. In particular, frequency relaxation follows the Vögel Fulcher law for the high grain sizes, whereas for intermediate sizes, two Debye processes are evidenced. This behavior as well as a diminution of the maximum of the real dielectric constant εmax could be explained within the mechanism of relaxation based on the existence of polar nanoregions with a core-shell structure for each grain.