Correlation of the crystal structure, bond characteristics, and microwave dielectric properties of (1-x)MgTiO3 – xCa0.5Sr0.5TiO3 ceramic for DRA applications

Abstract

In this current work, we report the impact of Ca_0.5Sr_0.5TiO₃ in the crystal structures, microstructures, and the dielectric performances in the microwave region on MgTiO₃ perovskite ceramic with standard formula of (1-x)MgTiO₃-xCa_0.5Sr_0.5TiO₃ [x = 0.025–0.1] (referred to as (1-x)MTO-xCSTO). The samples were prepared by employing the well-known solid-state reaction route. The crystal structure analysis was carried out using X-ray diffraction and Rietveld refinement confirms the existence of a dual phase in the composition. Scanning electron microscope techniques have been utilized to examine the crystal structure and microstructural characteristics of materials. The dense and homogeneous microstructures of (1-x)MTO-xCSTO materials have been verified by the SEM images. The various vibrational modes associated with the composition were identified from the Raman spectroscopy and the variation of the width of the spectra is correlated with the dielectric performance. The dielectric parameters were obtained from the vector network analyzer and the temperature coefficient (at the resonating frequency) and quality factor from the TE_01δ mode of (1-x)MTO-xCSTO compound. The bond strength, bond valency, and tolerance factor of the samples were correlated with the quality factor and temperature coefficient. The (1-x)MTO-xCSTO composition exhibits exceptional thermal stability due to a linearly zero temperature coefficient. The variation of quality factor with the variation of Ca_0.5Sr_0.5TiO₃ was correlated with the variation of the width of the Raman spectra. Among all the compositions, x = 0.05 shows a high-quality factor and nearly zero temperature coefficient.

Further, the infrared reflectance spectra of the optimum composition have been analyzed and the various phonon modes were identified using the standard harmonic oscillator model. Furthermore, the dielectric resonator antenna has been developed with (1-x)MTO-xCSTO ceramics as resonators, and several antenna parameters have been analyzed by HFSS software. The observed microwave dielectric properties and the antenna characteristics indicate that the (1-x)MTO-xCSTO (for x = 0.05) composition can be a prominent dielectric resonator for 5G applications operating at the C frequency band.