Electrophoretic Deposition of Ferroelectric Composites for Applications in Electronic Scanning Systems
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ELECTROPHORETIC DEPOSITION OF FERROELECTRIC COMPOSITES FOR APPLICATIONS IN ELECTRONIC SCANNING SYSTEMS. E. Ngo, P.C. Joshi, M. W. Cole, C. W. Hubbard Army Research Laboratory Weapons and Materials Directorate Attn: AMSRL-WM-MC; Building 4600 Email: [email protected] Aberdeen Proving Ground, MD 21005, U.S.A. ABSTRACT
We have investigated the electrophoretic deposition (EPD) as a low cost and conformal method of fabricating barium strontium titanium (BST) based composite thick films. The films were deposited at a controlled rate on platinum substrate in acetone-based slurry under electric bias. Acetone-aerosol OTS surfactant dispersion was used as dispersive medium. Conformal BST based thick films of 1080 µm were obtained. The dielectric constant and dielectric loss factor of Ba0.60Sr0.40TiO3 and Ba0.60Sr0.40TiO3 – 20wt% compositions were 603.3 and 0.029 and 327.0 and 0.002, respectively. The low frequency electronic properties of the electrophoretic films were also compared with those of the bulk BST ceramics. In addition, the optical and the structural properties of the films are also discussed. The various techniques employed include x-ray diffraction, SEM and surface profilometer.
in Tc below room temperature reduces the dielectric loss due to disappearance of the ferroelectric hysteresis. Electrophoretic deposition (EPD) is a simple, cost effective and conformal method of depositing thick films. The deposition occurs in a solution under bias. This phenomenon occurs due to the charge on the surface of the particle that is attracted to the opposite polarity on the surface of the DC
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I. INTRODUCTION Ba(1-x)Sr(x)TiO3 (BST) is a continuous solid solution between barium titanate and strontium titanate over the entire range of concentration. The Curie temperature of Ba(1x)Sr(x)TiO3 decreases linearly with increasing strontium titanate concentration. As a result, the transition temperature and, hence, the electrical and optical properties of Ba(1x)Sr(x)TiO3 can be tailored over a broad range to meet the requirements of various electronic applications. It has been reported that barium strontium titanate based composite materials, Ba(1-x)Sr(x)TiO3-MgO, posses significantly reduced dielectric constant and dielectric loss compared to that of pure Ba(1-x)Sr(x)TiO3.1 These BST-MgO bulk composite materials have also demonstrated excellent dielectric loss and dielectric tunability characteristics at X-band and K-band frequencies. By optimizing the Ba/Sr ratio and MgO content, the Curie temperature can be shifted below the room temperature making the material paraelectric under normal operating conditions. 2 The non-linearity of the dielectric properties with respect to applied DC voltage makes these composite materials attractive for tunable microwave devices particularly for phased array antenna. In addition, a decrease
Figure 1. Basic
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