Unraveling the dielectric and electrical properties of binary BaTiO3/Ba0.98Ca0.01Mg0.01Fe12O19 composites

Abstract

In this study, composite materials of barium titanate (BaTiO3 or BTO) phase embedded with different contents of Ba0.96Ca0.02Mg0.02Fe12O19 (BCMFO) hexaferrite phase as (BTO)1-x/(BCMFO)x (x = 0.00, 0.02, 0.05, 0.10, and 1.00) composites were prepared. The successful formation of the desired samples was established via X-ray diffraction. Additional peaks showing a chemical reaction between the two phases as a result of the heat treatment were not found. The co-existence of the two-component phases was further confirmed via field emission scanning electron microscopy and energy dispersive X-ray spectroscopy, wherein rounded spherical grains (with nanometric size < 200 nm) correspond to the BTO phase while plates-like shaped grains with larger size (with micrometric size) correspond to the BCMFO hexaferrite phase. This study also investigates the impact of the composition ratio of BCMFO to BTO composites on electrical and dielectric properties through comprehensive parameter-based analyses using impedance spectroscopy. Parameters explored include conductivity, dielectric constant, dielectric loss, dissipation factor, and complex modulus, alongside Nyquist analysis of Cole-Cole modulus functions. The activation energies range from approximately 40 to 431 meV. The study suggests the involvement of electron-hole hopping, polaronic, and ionic mechanisms in conduction within intra-grains and grain boundaries. Results reveal strong dependencies of all dielectric parameters on both frequency and composition ratio. Nyquist plots demonstrate distinct semicircles reflecting contributions from intra-grain, grain boundary, and BCMFO components. The extent of dielectric loss is found to be influenced by factors such as porosity, density, homogeneity, and grain size, influenced by sintering and composition conditions. The presence of these semicircles in Nyquist plots indicates different relaxation phenomena associated with charge carrier mobility within the grain boundary and the grain itself. Additionally, the diameter of these semicircles correlates with the resistance values of both grain boundary and grain. These findings suggest the potential for tuning dielectric parameters by adjusting composition ratios, particularly relevant for applications in micro-device technologies such as multilayer chip capacitors and multilayer chip inductors, facing new challenges.