Cuboidal vs equiaxed: The role of nanopowder assembly during BaTiO3 ceramic pressing step

The functional properties of BaTiO3 ceramics, produced by using the same pressing/sintering strategy from nanopowders with two distinct morphologies (cuboidal/equiaxed nanoparticles) and similar particle sizes, are comparatively investigated. The sintered ceramics exhibit similar nanoscale structures, with faceted crystalline grains and crystalline inclusions, clean grain boundaries and well-defined 90 degrees lamellar domains extending in some entire grains or finer nanodomains inside grain regions. The differences in the functional behavior originating from the different nanopowder morphology are described in terms of the nanoparticle assembly during the pressing step. The numerically simulated green body densification indicated a more efficient assembly resulting in higher density for the cubic particles (0.90 vs . 0.84 relative density) and a more homogeneous pore distribution in the spherical-derived ones. As a result of the higher density after sintering, the functional properties are enhanced in cuboid-originated ceramics. For comparison, the ceramic produced from cubic nanoparticles sintered at T-1 / T-2 = 1,250/800 degrees C shows higher permittivity (room temperature value of similar to 2100 - cubic vs. -1700 - rounded), enhanced ferroelectric characteristics (cubic: Ps = 8.57 mu C cm(-2) , Pr = 0.95 mu C cm(-2) , and Ec = 2.3 kV cm(-1) , with respect to Ps = 6.06 mu C cm(-2) , Pr = 0.4 mu C cm(-2) , and Ec = 1.4 kV cm(-1) , for spherical - derived ones, measured at E-max = 29.3 kV cm(-1) ) and a stronger dc-field dependence of their permittivity of similar to 12 % (cubic) vs. only similar to 2 % (spherical), for a dc-applied field in the range of -15 kV cm(-1) < E-dc < 15 kV cm(-1) . In contrast, the spherical particles-derived ceramics contain fewer defects and have a more homogeneous and finer porosity distribution in the ceramic volume and consequently, they are more stable and sustain larger field applications in comparison with the cubic-derived counterparts.