Colossal dielectric response in barium iron niobate ceramics obtained by different precursors

Ba(Fe_0.5Nb_0.5)O₃ (BFN) ceramics were synthesized by a traditional mixed oxide method (BFN-M), as well as a columbite method (BFN-C) with FeNbO₄ precursor. X-ray diffraction reveals that both the ceramics and precursor have a pure monoclinic phase. BFN-C samples showed improved microstructure with less pores and smaller grain size. Dielectric properties of the BFN ceramic were characterized in a broad frequency range (0.1 Hz to 10 MHz) and a temperature range from -120 to 300 °C. A Debye-like relaxation was found in a low-frequency range, where a high-temperature dielectric anomaly was observed too. The relative low-dielectric loss suggests that columbite method should be a better choice for the synthesis of A(Fe_0.5B_0.5)O₃ ceramics.