abstract
The orientation and grain aspect ratio, size and distribution of BaLa4Ti4O15 (BLT) ceramics have been studied as a function of sintering temperature with a view to elucidating a general principle by which the microwave properties (MW) can be understood/tuned in systems which exhibit anisotropic grain structures. For BLT sintered at 1500 degrees C, epsilon(r) reaches a maximum of 51, with tan delta minimum at 0.002 and tau(epsilon r) = -17 ppm/degrees C but epsilon(r) subsequently varies non-linearly as sintering temperature increases. Since epsilon(r) and tau(epsilon r) are directly proportional in the absence of a phase transition, the variation of tau(epsilon r) as a function of the sintering temperature is also nonlinear. This behaviour is related with variations in the orientation and grain aspect ratio, size and distribution with the sintering temperature and it is demonstrated that by controlling sintering conditions, microwave dielectric properties can be tuned. It is proposed that this is a general phenomenon which can also be used to explain the variation and tune the properties of other ceramic systems with anisotropic grain structures. (C) 2016 Elsevier Ltd. All rights reserved.
keywords
PEROVSKITE-RELATED COMPOUNDS; COMPOSITE CERAMICS; THICK-FILMS; MICROSTRUCTURE; PERMITTIVITY; (BA
subject category
Materials Science
authors
Mahajan, A; Reaney, IM; Vilarinho, PM
our authors
Amit Mahajan
PhD Student
Paula Maria Lousada Silveirinha Vilarinho
Vice Directoracknowledgements
The authors acknowledge Fundacao para a Ciencia e a Tecnologia (FCT), Fundo Europeu de Desenvolvimento Regional Portugal (FEDER), QREN-COMPETE Portugal, and the Associate Laboratory CICECO (PEst-C/CTM/LA0011/2013) for funding support. Amit Mahajan acknowledges FCT for financial support (SFRH/BD/65415/2009).