Co-firing of spatially varying dielectric Ca-Mg-silicate and Bi-Ba-Nd-titanate composite

A spatially variant dielectric Ca-Mg-silicate (CMS)/Bi-Ba-Nd-titania (BBNT) composite, in which periodic BBNT inclusions were embedded in the CMS matrix, was fabricated using the thermoplastic extrusion. The co-firing behavior of the composite was evaluated in terms of its shrinkage compatibility, thermoplastic compatibility, and chemical compatibility. The noticeable shrinkage mismatch between CMS and BBNT materials was observed. Such shrinkage mismatch strongly affected the interfacial bonding types of the composites. The good interfacial bonding was observed for the composite having BBNT inclusions in the CMS matrix; however, the interfacial cracking and matrix cracking for the opposite design (i.e., CMS inclusions in the BBNT matrix). In addition, the (Ca, Zn)-rich glassy phase in the CMS region migrated into the BBNT region, forming an interfacial reaction layer. The dielectric properties of the CMS, BBNT, and CMS-BBNT mixture were measured to evaluate the spatially variant dielectric CMS/BBNT composite as a novel dielectric substrate.