Efeitos da adição de TiO2 nas propriedades elétrica da matriz Sr2TiSi2O8 e suas aplicações em ressoadores dielétricos (Banda C)

Abstract

In this work, we present the study of electric properties in the radiofrequency (RF) region (f < 300 MHz) and microwaves (MW) (300 MHz < f < 300 GHz) of the ceramic matrix Sr2TiSi2O8 (STS) with the addition of TiO2 and its applications in dielectric resonator antennas (DRA) and telecommunication systems. We conducted X-ray diffraction and scanning electron microscopy (SEM) analyses for material

characterization and determination. Complex impedance spectroscopy (CIS) techniques were applied to investigate the electrical properties of the matrix and composites. High relative dielectric permittivity (ε′r) values were obtained for STS20 (ε′r = 2.8×103), STS15 (ε′r = 2.2×103), and STS25 (ε′r = 1.8×103) after the addition of TiO2. Nyquist diagrams were used to measure the contributions of grains and grain boundaries to the electrical response of the samples in an R-CPE circuit association. The samples exhibited grains and grain boundaries (340 °C to 460 °C) with decreasing resistance as temperature increased. The temperature coefficient of capacitance (TCC) at low frequencies was more influenced by temperature. In the microwave region, the addition of TiO2 improved the dielectric performance of the material by increasing the dielectric permittivity (εr) and reducing the dielectric losses (tanδ) at moderate concentrations, with tanδ values of 1.75×10−2 for STS and tanδ = 2.02×10−3 for STS20. The temperature coefficient of resonant frequency (τf) showed a value of –22.30 ppm/°C. In numerical simulations, the results were excellent, with a directivity of 5.79 dBi, a gain of 4.38 dBi, and a radiation efficiency of 72.15% for STS, as well as 97.99% efficiency for the STS25 sample. The results demonstrate that the samples can operate in C-band electronics (4 GHz < f < 8 GHz) as defined by the Institute of Electrical and Electronics Engineers (IEEE). This range is suitable for applications in high-frequency Wi-Fi devices, 5G networks, and weather radar systems.