Effects of various oxide fillers on physical and dielectric properties of calcium aluminoborosilicate-based dielectrics

Physical and dielectric properties of LTCC (low temperature co-fired ceramics) materials based on a typical calcium aluminoborosilicate glass and various fillers such as Al₂O₃, BaTiO₃, CaTiO₃, TiO₂, ZrO₂, MgO and SiO₂ were investigated. Densification, crystallization and thermal and dielectric properties were found to strongly depend on the type of filler. The XRD patterns of Al₂O₃, BaTiO₃, CaTiO₃ and MgO samples demonstrated crystalline phases, CaAl₂Si₂O₈, BaAl₂Si₂O₈, CaTiSiO₅ and CaMgSi₂O₆, respectively, as a result of firing at 850 °C. For the sample containing CaTiO₃ filler, specifically, dielectric constant increased drastically to approximately 19.9. A high quality factor of >210 and a high TCE (temperature coefficient of expansion) of >8.5 ppm/°C were obtained for the composition containing MgO or SiO₂. Near zero TCF (temperature coefficient of frequency) was obtained for the samples containing TiO₂. The purpose of this work is to investigate the effects of various ceramic fillers on physical and dielectric properties and ultimately to provide the technical guidelines for the proper choice of filler in various LTCC systems.