Keywords: lead-free, ferroelectric relaxor, perovskites Relaxor ferroelectrics are used for applications in a wide variety of devices [1]. The great interest of these materials is related to their very high dielectric permittivity observed in the large range of temperature and the strong frequency dispersion at low temperature [2]. To understand the origin of this behaviour many works based on structural and physical models are performed. The relaxor behaviour occurs generally in complex perovskite of formula (A'A')'(B'B'')O 3 where two (or more) cations of different valences are located in the equivalent crystallographic positions. Relaxor materials actually used are lead-based ceramics which present a disadvantage due to the toxicity of PbO. The actual evolution of research is oriented to environment friendly application. In this way, the present work concerns new lead-free compositions of non-stoichiometric perovskite derived from the well known BaTiO 3. Dense ceramics were obtained by conventional mixed oxide method. Room temperature X-ray diffraction analysis allowed us to determine the limits of solid solution. Dielectric measurements were performed on ceramic disks. For all samples, the temperature and frequency variations of the real and imaginary part of permittivity are investigated. The results are discussed and compared to previous works concerning the Ba 1-x A 2x/ 3TiO 3 compositions where La and Bi are in the dodecahedral sites (A) [3,4]. The performed study has shown that the relaxor behaviour is not due only to the B-site order/disorder. The role of the cation in the A-site seems to be also important [5].

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