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

authors	Kaushal, A; Olhero, SM; Antunes, P; Ramalho, A; Ferreira, JMF
nationality	International
journal	MATERIALS RESEARCH BULLETIN
author keywords	Oxides; Electronic materials; Microstructure; Mechanical properties; Dielectric properties
keywords	GRAINED BARIUM-TITANATE; MICROWAVE DEVICES; SPINEL POWDER; THICK-FILMS; CERAMICS; FINE; FERROELECTRICS; PERMITTIVITY; SUSPENSIONS; COMPOSITES
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.
publisher	PERGAMON-ELSEVIER SCIENCE LTD
issn	0025-5408
year published	2014
volume	50
beginning page	329
ending page	336
digital object identifier (doi)	10.1016/j.materresbull.2013.11.028
web of science category	Materials Science, Multidisciplinary
subject category	Materials Science
unique article identifier	WOS:000331920500054