Structural, mechanical and dielectric properties of Ba0.6Sr0.4TiO3—The benefits of a colloidal processing approach

• We synthesize micro-sized granules of Ba0.6Sr0.4TiO3 electroceramic material.
• The study disclosed a need of protecting BST powders against hydrolysis.
• An improvement in various properties of BST-FG has been observed.
• Study shows an in-depth understanding of processing electroceramics in water media.

This paper reports on the benefits gathered from a proper colloidal dispersion/deagglomeration of a Ba0.6Sr0.4TiO3 (BST) powder in water followed by spraying the aqueous suspension against liquid nitrogen to obtain homogeneous granules. The density of green compacts derived from the freeze granulated (FG) powder was compared with that of compacts prepared from the same starting BST powder but non-granulated (NG). The sintering ability of the greens and the density, mechanical and functional properties of the obtained ceramics sintered at various temperatures properties were shown to be strongly enhanced by the freeze granulation step. Freeze granulation enabled decreasing the optimal sintering temperature for 50 °C, and enhanced all the relevant measured properties, which showed a good correlation with sintered density. Maximum values of dielectric constant (εrmax=5087εrmax=5087) and dielectric loss (tan δ = 0.009) were measured at the phase transition temperature (Tc = −3 °C) and at a constant frequency of 10 kHz for the FG BST ceramics sintered at 1250 °C, which also showed a flatter temperature-dependent dielectric profile.

Spherical freeze granules of BST materials.Figure optionsDownload as PowerPoint slide