abstract
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 degrees C, and enhanced all the relevant measured properties, which showed a good correlation with sintered density. Maximum values of dielectric constant (epsilon(rmax) = 5087) and dielectric loss (tan delta = 0.009) were measured at the phase transition temperature (T-c = -3 degrees C) and at a constant frequency of 10 kHz for the FG BST ceramics sintered at 1250 degrees C, which also showed a flatter temperature-dependent dielectric profile. (C) 2013 Elsevier Ltd. All rights reserved.
keywords
GRAINED BARIUM-TITANATE; MICROWAVE DEVICES; SPINEL POWDER; THICK-FILMS; CERAMICS; FINE; FERROELECTRICS; PERMITTIVITY; SUSPENSIONS; COMPOSITES
subject category
Materials Science
authors
Kaushal, A; Olhero, SM; Antunes, P; Ramalho, A; Ferreira, JMF
our authors
Ajay Kaushal
Post-Doc Fellowship
José Maria da Fonte Ferreira
Retired Professor
Susana Maria Henriques Olhero
Assistant ProfessorProjects
Development of microelectromechanical systems by gelcasting - GELMEMS (PTDC/CTM/099489/2008)
acknowledgements
A. Kaushal and S.M. Olhero would like to thank the Foundation for Science and Technology of Portugal (FCT) for the financial support under the grants SFRH/BPD/77598/2011 and SFRH/BPD/87486/2012, respectively. The authors would also like to thank CICECO for the work at the University of Aveiro and FCT for the financial support under the project PTDC/CTM/099489/2008.