Sintering of layered ferrite-BaTiO3 ceramics: Analysis of interfaces and effects of shrinkage mismatch

In the present work, densification and microstructure evolution of cobalt ferrite (FCO), nickel-cobalt ferrite (FNICO) and BaTiO3 (TB) ceramics under different sintering conditions were investigated. Subsequently, layered ferrite-BaTiO3 samples were formed by uniaxial pressing of the corresponding ceramic powders. These green samples were sintered with two different sintering schedules, aiming to study the ferrite-BaTiO3 interfaces after sintering. The analyses were made at the cross section of the interfaces and at the interface surfaces after separation of the layers. The sintered layered samples were utilized to analyze sintering mismatch, diffusion at the interfaces and identification of some newly formed phases. EDS analysis across the TB-FCO interface showed evidences of diffusion. It was observed that the FNICO layers were detached from TB during sintering, but the same was not observed in the TB-FCO samples, although shrinkage mismatch resulted in some defects. XRD analyses suggested the presence of Ti2O at the TB-FCO interface and BaTiNiFe10O19 at the TB-FNICO interface as products of the reactions between the ferrites and BaTiO3.