Dielectric Characterization of (Bi_(1-x)Fe_x) NbO_4 Ceramics Prepared by Wet-Chemical Route

摘要

(Bi_(1-x)Fe_x)NbO4 powders with 0.00 ≤ x ≤ 0.75 were prepared by a wet-chemical route. Pellets from these powders were made and sintered at temperatures between 500 and 1100 °C. The dielectric properties were analyzed as a function of the thermally activated structural and morphologic evolution. The structure was studied by X-ray diffraction (XPD) and the morphology by scanning electron microscopy (SEM). The XRD results revealed that the substitution of bismuth by iron was successful for x = 0.25 and 0.50, with the formation of the non-stoichiometric phases Bi_(1.34)Fe_0._(66)Nb_(1.34)O_(6.35) and Bi_(1.721)Fe_(1.056)Nb_(1.134)O_7. The dielectric properties were measured by impedance spectroscopy method in the frequency range of 10~2–10~6 Hz as a function of temperature (200-330 K). For the samples with x ≥ 0.25 treated at 800 and 1100 °C, the dielectric constant and the dielectric losses remain practically constant with the frequency and temperature. The dielectric relaxation mechanisms were studied using the complex modulus formalism.