Effects of spark plasma sintering on ferroelectricity of 0.8Bi(3.15)Nd(0.85)Ti(3)O(12)-0.2CoFe(2)O(4) composite ceramic

摘要

The 0.8Bi(3.15)Nd(0.85)Ti(3)O(12) (BNdT)-0.2CoFe(2)O(4) (CFO) composite multiferroic ceramics have been fabricated by spark plasma sintering (SPS) at 850 degrees C. The relative density of as-sintered SPS ceramic reaches 97.4 (+/- 0.3)%. The composites are composed of pure BNdT and CFO phases without any preferred c-orientation. The a-orientation preference is more obvious perpendicular to the pressure direction. The average grain-sizes of BNdT and CFO are 163 and 146 nm, respectively. The BNdT phase has more grains below 100 nm (similar to 20%). The super energy-dispersive X-ray analyses suggest no serious reaction between BNdT and CFO. The Raman spectrum verifies the nano-structure of the SPS ceramic via the broadening bands and peak shifts. The Curie temperature of the SPS ceramic declines to 560 degrees C with stabilized dielectric loss. The grain boundary resistance plays a dominant role on impedance above 700 degrees C. The remanent polarization approaches to 15.2 mu C/cm(2) (300 kV/cm) with lower coercive fields (-89/+95 kV/cm).