Colossal relative permittivity and low dielectric loss in BaFe0.5Nb0.5O3 ceramics prepared by spark plasma sintering

Abstract

BaFe0.5Nb0.5O3 (BFN) ceramics has been prepared using a rapid process where the powder was synthesised using mechanical milling of the components then consolidated by spark plasma sintering (SPS) for 5 min at 1100 °C. X-ray diffraction results confirmed the pure cubic phase of the prepared SPS BFN ceramic. The average grain size as measured by SEM analysis was ~300 nm. Complex impedance measurements revealed giant dielectric constant (ε′ ~ 2.3 × 104) and low dielectric loss (tanδ ~ 0.48) for the SPS BFN ceramic at room temperature and 1 kHz. Two thermally activated relaxation peaks were observed in the spectra of imaginary part of modulus (M″). These relaxations were attributed to the Debye-like relaxation process in grains (at high frequency and low temperature) and non-Debye Maxwell-Wagner (M-W) polarization effect at grain-boundary (at low frequency and high temperature).

Keywords

• Ball-mill
• Spark plasma sintering
• Ceramics
• Dielectric properties
• Impedance spectroscopy