The perovskite sample La0.7Sr0.25Na0.05Mn0.7Ti0.3O3 (LSNM0.70T0.30) was produced via a solidstate route process. Impedance spectra of LSNM0.70T0.30 in the frequency interval [40Hz -1MHz] were studied at several temperatures [80K to 440 K]. The ac conductivity (ac) established that according to the Jonscher law. ac is described by Non-overlapping Small Polaron Tunneling model at low temperatures and Correlated Barrier Hopping model at high temperatures. From dc conductance analysis, conduction seems to be thermally activated, suggesting the existence of semiconductor process. Detailed investigation of impedance data revealed the non-Debye nature of the relaxation processes in the sample. In addition, Dielectric constant curves were applied to examine the relaxation dynamics of charge carriers. In fact, the Debye-like relaxation was performed on the basis of the polarization of spatial charges following Maxwell-Wagner model and Koop's phenomenological theory.

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The aim of this paper is to study performance enhancement of the dielectric properties of polycrystalline Ba 0:8 Sr 0:2 Ti ð1ÀxÞ Sn x O 3 , with 0 x 0:2. The material was characterized by x-ray diffraction, scanning electron microscopy (SEM), micro-Raman spectroscopy and impedance spectroscopy technique. The results have been analyzed by studying the effects of substituting Sn 4+ for Ti 4+ . The observed diffraction peaks have been indexed to a cubic structure with space group Pm3m. The calculated lattice parameters increase from 3.9834 Å to 4.0091 Å with increasing Sn concentration. The SEM micrographs show that with increasing Sn an increase of the grain size from x = 0 up to x = 0.15 was observed. The dielectric measurements confirm the relaxor behavior of all the concentrations of Ba 0:8 Sr 0:2 Ti ð1ÀxÞ Sn x O 3 compounds. The Ba 0:8 Sr 0:2 Ti 0:95 Sn 0:05 O 3 compound presents the most interesting properties, namely high dielectric constant value (e 0 ðT m Þ ¼ 5017) and a Curie temperature slightly above room temperature ðT c ¼ 317KÞ. An important dielectric constant value persists for a wide range of temperatures around room temperature. This is considered as an advantage of the Ba 0:8 Sr 0:2 Ti 0:95 Sn 0:05 O 3 relaxor ferroelectrics.