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چکیده
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As a material of interest for multilayer ceramics, BaTiO3 has been receiving great attention from researchers in recent years. In the thermally harsh environment with the application of electronic devices, the inability of pure BaTiO3 ceramics to meet the temperature stability requirements due to the change in the dielectric properties at the Curie temperature (Tc), the performance is improved by developing a series of systems based on BaTiO3 through the doping method. Among them BaCaTiO3 and Strontium zinc titanate (SZT) which has a chemical formula SrZn0.5Ti0.5O3. In this thesis, BaCaxTi1-xO3 (BCT) and (1−y)BaCa0.05Ti0.95O3–(y)SrZn0.5Ti0.5O3 (BCT:SZT) powders, for x= 0 ≤ x ≤ 0.08, 0.1 ≤ y ≤ 0.2, were fabricated by solid-state method. In addition, multi-stacked films synthesized by laser technique, deposited on glass coated gold (Au) as electrodes; the Au coated glass was prepared using sputtering technique, for Nano-electronic devices. The ceramic powders were fabricated at low temperature. Starting with different precursors; the TiO2 (anatase Nanoparticles and bulk powders), BaCO3/TiO2, the Ba(OH)2/TiO2, and Ba(NO3)2/TiO2 powder mixtures, to achieve the best mixture in terms of crystal structures. It was found that, a tetragonal structure BaTiO3 was formed after centering at 1100 °C for 2h. The XRD analyses were used to investigate the crystal structures of fabricated BaTiO3 based ceramics. The FESEM analysis of the prepared powder was used to suggest a realistic approach describing the reaction mechanism of the ceramic powders. Characterizations and the dielectric characteristics of the sintered ceramic powders were detected. The plane (110) of (BCT) Ca doped BaTiO3 powders shifted to the higher angles due to substitution of Ti4+ ion by Ca2+ ion by a factor x. That happened might be due to the difference in ionic radii of Ca2+ (1.14 Å), and Ti4+ (0.745 Å), and have different values of electrovalence. Moreover, the phase analysis for (BCT:SZT) (1-y)BaCa0.05Ti095O3 –ySrZn0.5Ti0.5O3, the plane (110) shifted to the higher angles also due to substitution of Ti4+ ion by Zn2+ ion by a factor y, thus, it directly affected the BCT compound when added. A high dielectric constant detected with Pure (BT) BaTiO3, and then decreased upon addition of calcium ions in (BCT) BaCaTiO3. The Tangent loss was (˂ 0.04) and then decreased as the frequency increased. Thermal stability was detected with BaCaxTi1-xO3 and (1−y)BaCa0.05Ti0.95O3–(y)SrZn0.5Ti0.5O3. Upon increase in x, y lower temperature stability was enhanced towards room temperature, but high temperature stability degraded. The dielectric maxima peak becomes broader, with Tangent loss (Tan δ) being (˂ 0.02) especially with (SZT) SrZnTiO3 adding, means that SZT doping led to a lower dielectric loss. From another hand, the dielectric constant value of the multi-layer increased at temperature degree 25 oC. Then decreased as increasing temperature with increasing Ca concentration due to reduced tetragonality of BCT compared with BT. Moreover, the (Tc) shifted toward room temperature, and increased the width of the dielectric peak as increased Ca concentration, which significantly enhanced the dielectric properties stability at low temperatures. In addition, the optical characteristics of the samples investigated by UV-Vis are in this thesis.
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