Available free online at www.medjchem.com Mediterranean Journal of Chemistry 2019, 8(2), 198-208 *Corresponding author: Mohammed Mesrar Received February 10, 2019 Email address: mohammed.mesrar@usmba.ac.ma Accepted March 23, 2019 DOI: http://dx.doi.org/10.13171/mjc8319050908mm Published May 9, 2019 Effect of barium doping on electrical and electromechanical properties of (1-x)(Na 0.5 Bi 0.5 )TiO 3 -xBaTiO 3 Mohmmed Mesrar 1,* , Tajdine Lamcharfi 1 , Nor-Said Echatoui 1 , Farid Abdi 1 , Fatima Zahra Ahjyaje 2 and Mustapha Haddad 3 1 Signals, Systems and Components Laboratory (LSSC), USMBA, FST-Fez, Imouzzer road B.P 2202, Morocco 2 Laboratory of Materials, Natural Substances, Environment and Modeling (LMSNEM), Polydisciplinary Faculty of Taza, USMBA, Imouzzer road B.P 2202, Morocco 3 Spectrometry, Materials and Archaeomaterials Laboratory (LASMAR) Abstract: The effect of Barium doping is studied on ferroelectric properties of (1-x)(Na 0.5 Bi 0 . 5 )TiO 3 -xBaTiO 3 with( x = 0.00; 0.0 3; 0.05; 0.06; 0.07; 0.08 and 0.10) prepared through solid state sintering route. X-ray diffraction along with Rietveld refinement revealed a gradual change in crystal structure from rhombohedral to tetragonal with increasing BaTiO3 doping in the compound. SEM images have shown a uniform distribution of grains and change in grain size with BaTiO 3 concentration. Dielectric and dispersive studies have been carried out. The rhombohedral distortion of the unit cell slightly increased and ferroelectric transition temperature, T m decreased with the increase of Barium content and all compositions of (1-x)(Na 0.5 Bi 0 . 5 )TiO 3 -xBaTiO 3 ceramic materials reveal diffuse phase transition that is marked by a strong frequency dispersion of the permittivity which would be related with the cation disorder in the A site of the unit cell. Combined impedance and electrical propriety were used to analyze impedance data. The electromechanical parameters were calculated from the resonant and anti-resonant frequencies from the evolution of the permittivity according to the frequency plots. The electromechanical coefficients for (1-x)(Na 0.5 Bi 0 . 5 )TiO 3 -xBaTiO 3 with all compositions were found to be much larger than that of pure Na 0.5 Bi 0.5 TiO 3. Keywords: Dielectric properties; Resonant frequency; Anti-resonant frequency; Complex impedance plots. Introduction The investigation of the electrical properties of (1-x)(Na 0.5 Bi 0 . 5 )TiO 3 -xBaTiO 3 had been and still is a very important research problem because of its scientific importance and the difficulty of explain- ning the behavior fundamental. The electrical resistance and ferroelectric transition temperature can be controlled effectively by doping in A-site between (Na/Bi) and Ba ions 1 . Barium titanate and its related compounds have been widely used in the manufacture of ceramic capacitors and resistors. Since its discovery, BaTiO 3 has been used as a high permittivity capacitor material because of its high dielectric constant 2 . Variation in chemical composi- tion or thermal treatment in these ceramics led to quite drastic changes in physical properties while retaining substantially piezoelectric properties 3 . NBT has a relatively large remanent polarization (Pr=38μC/cm 2 ), exhibiting a high Curie tempera- ture (T c =320°C) and a high coercive field (E c =73kV /cm) at room temperature, also presents a relatively large conductivity 4 . Jones et al reported at ambient temperature, which this compounds are rhombohedral and described with R3c symmetry with polar cation displacements combined with anti-phase rotations of oxygen octahedral 5 . Dielectric behavior of the NBT-based system is ferroelectric at room temperature, on increasing temperature ferroelectric to anti-ferroelectric phase transition has been reported at ~220 o C defined as T d , the second transition occurs around 320 o C abbreviated as T m corresponding with to a transition from the anti-ferroelectric to paraelectric phase 6 . The aim of the present investigation is to apply the variable- frequency techniques of impedance spectroscopy to Barium doped (Na 0.5 Bi 0 . 5 )TiO 3 to probe some of the above aspects and seek to obtain the correlation between the disorder on site A(Na/Bi) and relaxor behavior of these compositions. Experimental Details Ceramic samples were prepared by applying the conventional ceramic sintering technique. The samples were fabricated using grade (99.99% pure) Na 2 CO 3 , Bi 2 O 3 , TiO 2 and BaCO 3 . The investigated compounds are (1-x)(Na 0.5 Bi 0 . 5 )TiO 3 -xBaTiO 3 with