Investigation of relaxor and diffuse dielectric phase transitions of Ba(1-X)Bi(x)Ti(0.8)Fe(0·2)O(3) materials

Different doping elements have been used to enhance the dielectric properties of BaTiO(3) ceramic. In this work, the effect of substitution of Ba by Bi in A site and Ti by Fe in B site on structural, dielectric and electrical properties of Ba(1-x)Bi(x)Ti(0.80)Fe(0·20)O(3) ceramics at (x = 0.00, 0.05, 0.10 and 0.15) was investigated by X-ray diffraction, Raman spectroscopy, Scanning Electron Microscopy (SEM), Mössbauer spectroscopy as well as dielectric measurements. The Rietveld refinement results revealed that the prepared compounds crystallize in both tetragonal (P4mm) and hexagonal (P6(3)/mmc) phases for x = 0.00 and 0.05 while at x = 0.10 and 0.15, the hexagonal phase disappears and only the tetragonal phase is fitted. The Raman spectra confirmed the disappearance of hexagonal phase in benefit of tetragonal phase as the Bi(3+) substitution increases. Based on Mössbauer analyses results, all the samples are in paramagnetic state at room temperature and the Fe is oxidized under Fe(3+) without the presence of Fe(2+) or Fe(4+) ions. The dielectric measurements as function of temperature are studied and tree broad and relaxor phase transitions were detected: from rhombohedral to orthorhombic phase T(R-O) and to tetragonal ferroelectric phase T(O-T) then to cubic paraelectric phase T(m). These phase transitions were displaced to the lower temperature with increasing of Bi(3+) substitution. The values of ε′(r) increase gradually with increasing of Bi(3+)contents which confirmed the enhancement of dielectric properties of BaTi(0·80)Fe(0·20)O(3) by Bi substitution on Ba site. The diffuse phase transitions were described by fitting the modified Uchino relation. The Cole–Cole analyses showed that both the grain and grain boundaries resistivity values are higher for Bi(3+) substituted samples which are responsible to the dielectric properties improvement.