abstract
An alternative approach to tailor the temperature coefficient of permittivity (TC epsilon(r)) of high Q dielectric BaO-Re2O3-TiO2 (Re: rare earth elements) thick films is presented. 10- to 80-mu m-thick BaNd2Ti5O14 (BNT) films are fabricated by electrophoretic deposition on Pt foils under different processing conditions. Observed anisotropic grain growth is facilitated by constrained sintering. The increase of the sintering temperature increases markedly the aspect ratio of the grains, decreases the dielectric permittivity and TC epsilon(r), changes from -114 to +12 ppm degrees C-1. By controlling the sintering temperature, near-zero TC epsilon(r), high Q thick films can be fabricated with 45 < epsilon(r) < 70. These findings are of technological relevance since they demonstrate that control of substrate constraint and sintering conditions can be used to control grain anisotropy and thus microwave properties of the BaO-Re2O3-TiO2. The thick films facilitate scaling to small device sizes for high frequency operation. Similar observations are expected in other microwave systems thus opening further technological opportunities.
keywords
MICROWAVE CERAMICS; PHASE-EQUILIBRIA; RIGID SUBSTRATE; SOLID-SOLUTION; BAO.ND2O3.5TIO2; IMPROVEMENT; RESONATORS; EVOLUTION
subject category
Chemistry; Science & Technology - Other Topics; Materials Science; Physics
authors
Fu, Z; Vilarinho, PM; Wu, AY; Kingon, AI
our authors
Aiying Wu
Researcher
Paula Maria Lousada Silveirinha Vilarinho
Vice Directoracknowledgements
The authors acknowledge Prof. Ian Reaney from the Department of Engineering Materials of the University of Sheffield for profitable discussions, Rosario Soares from the Central Laboratory of the University of Aveiro for the assistance with experiments that supported the construction of pole figures, and an anonymous referee for constructive suggestions leading to this present version. The authors appreciate the financial support from FCT and FEDER, Portugal and the EuropeanNetwork of Excellence FAME, under the contract FP6-500159-1. FuZhi acknowledges FCT for financial support (SFRH/BD/19327/2004).