Increased thermal stability and dielectric properties of Ba2TiSi2O8-CaTiO3 composites for high frequency applications

This work investigated composites formed from Ba₂TiSi₂O₈ – CaTiO₃ in the microwave region, as well as their dielectric properties, dielectric permittivity (ε’_r), dielectric loss (tan δ), and quality factor (Q x fr). Solid-state synthesis was employed for the preparation of the Ba₂TiSi₂O₈ ceramic matrix and the composites were obtained by mixing the matrix with 1%, 3%, 5% and 9% CaTiO₃ by weight. The structural characterization was performed through X-ray diffraction (XRD), and the phases were confirmed by Rietveld refinement. Scanning electron microscopy (SEM) was performed to analyze the surface morphology of the samples. The temperature coefficient of resonant frequency (τ_f) was obtained to verify the thermal stability of the samples. An analysis of τ_f, obtained through the Silva-Fernandes-Sombra (SFS) method, revealed that the addition of 5% CaTiO₃ provided a significant improvement in the thermal stability of the material (BTS5, τ_f = − 9.57 ppm∙ºC^− 1). It is noteworthy that the value obtained for this parameter is within the range required for applications in electronic devices operating in the microwave region. The Hakki-Coleman method was used to analyze the dielectric properties of the samples in the microwave region, through which it was possible to observe a subtle increase in the dielectric permittivity (11.00 ≤ ε’_r ≤ 16.71) and a decreased level of the dielectric loss (tan δ) of the samples. Finally, the dielectric resonator antenna (DRA) configuration was used to analyze the potential of the samples operating in the HE_11δ mode.