Nano-ferroelectric based core-shell particles: towards tuning of dielectric properties

For microwave agile devices such as tunable resonators or phase shifters, low loss components exhibiting electric-field dependent dielectric properties are seeked. Ferroelectric/low loss dielectric composites are good candidates to improve dielectric properties of BaxSr1-xTiO3 (BST) for such applications. Nanosized ferroelectric powders have been successfully encapsulated in a thin surrounding shell made of a binary oxide. The conservation of the ferroelectric transition in the composite has been shown while preserving the size of the ferroelectric cores after sintering. The dielectric properties of the composite can be tuned by changing the relative core/shell sizes, the intercore distance, the nature of the dielectric phase. Various synthesis routes have been used according to the required design of the final nanocomposite. Dielectric performances are presented and compared among the different nano-ferroelectric core-shell based particles obtained. (C) 2004 Elsevier Ltd and Techna Group S.r.1. All rights reserved.