화학공학소재연구정보센터
Advanced Functional Materials, Vol.19, No.7, 1071-1081, 2009
Textured Microstructure and Dielectric Properties Relationship of BaNd2Ti5O14 Thick Films Prepared by Electrophoretic Deposition
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.