摘要
The functional properties of BaTiO_(3)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°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)=1250/800℃shows higher permittivity(room temperature value of∼2100-cubic vs.∼1700-rounded),enhanced ferroelectric characteristics(cubic:P_(s)=8.57μC cm^(-2),P_(r)=0.95μC cm^(-2),and E_(c)=2.3 kV cm^(-1),with respect to P_(s)=6.06μC cm^(-2),P_(r)=0.4μC cm^(-2),and E_(c)=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∼12%(cubic)vs.only∼2%(spherical),for a dc-applied field in the range of-15 kV cm^(-1)<Edc<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.
基金
supported by the Romanian Ministry of Education and Research,CNCS-UEFISCDI Research Grant No.PN-Ⅲ-P1-1.1-PD-2021-0531.
