Preparation and properties of porous BaTiO3 nanostructured ceramics produced from cuboidal nanocrystals

Abstract

The preparation and properties of BaTiO3 nanostructured ceramics with porosity level in the range of percolation limit (33% and 37% porosity) produced by partial sintering of cubic nanoparticles are presented. Hydrothermally synthesized cuboid-like particles were produced by using Field-Assisted Sintering Technique facility in which temperature and pressure were selected to ensure the consolidation of mechanically stable porous nanoceramics, while preserving as much as possible the starting grain shape. Nanosized grains in the range of (10–40) nm and multiscale porosity ranging from a few nm to hundreds of nm were observed in the sintered ceramics. The dielectric constant of porous nanoceramics assumes low values of ~280–320 and shows a flat thermal response typical to nanostructured ceramics, without a net ferroelectric-paraelectric peak, followed by a Curie-Weiss dependence in the paraelectric state, with negative Curie Weiss temperatures and lowered Curie constant, as result of porosity and ultrafine grain size. A strong conductivity relaxation around room temperature related to air-ceramic interface phenomena indicated a possible sensitivity of these ceramics for gas sensing. Preliminary qualitative tests with saturated acetone vapours have shown a good response of both resistive and reactive components of such porous BaTiO3 nanoceramics and possible gas sensing interface-related mechanisms were discussed.