Molibdato de zinco (ZnMoO4) e seus compósitos com TiO2 para aplicações em componentes de alta frequência em comunicações

Abstract

Currently, the telecommunications area presents new demands and, consequently, challenges in the development of antennas, among them, the need for higher data transmission and greater information transport capacity. Thus, research into new dielectric ceramics ensures the evolution of telecommunications systems. In this work, the dielectric properties of composites based on zinc molybdate and titanium dioxide (ZnMoO4-TiO2) and possible application as dielectric resonator antenna (DRA) was investigated. The ZnMoO4 phase (ZMO) and its ceramic composites were obtained at low sintering temperatures in the proportions of 0.22, 0.27, and 0.36 in mole % of TiO2 and identified by X-ray diffraction. The insertion of TiO2 in the ZMO altered the structural characteristics and consequently the dielectric properties. In the radio frequency (RF) range, the samples exhibit low values of relative permittivity (εr) and dielectric loss tangent (tan δ), where their values decrease as frequency increases. The normalization curves showed the presence of short-range movement of charge carriers, with a thermally activated relaxation process (formation of relaxation peaks). The conductivity (σ) inthe samples obeys Jonscher's power law. Similar activation energies (Ea) (σdc e pela Z”) indicate that the samples have the same insulating character. The ZMT36 sample is the only one that does not show RF thermal stability in the range of 100 kHz to 1 MHz. The Nyquist diagrams were well adjusted using an equivalent electrical circuit, making it possible to measure the contributions of the grain region and grain boundary of the material in the electrical response of the samples. The measurements in microwaves (MW) show that these materials have low εr and tgδ, and the TiO2 addition in mol of 0.22 and 0.27 have a resonant frequency temperature coeficiente tend to zero (– 7.39 and + 2.18 ppm °C-1, respectively). In antenna measurements, ZnMoO4 showed a gain of 4.63 dBi, radiation efficiency of 82.37%, and bandwidth of 1.147 GHz. All composites had their properties improved and exhibited good performance in terms of gain above 5 dBi, bandwidth (498 – 622 MHz), efficiency above 97%, and operating frequency range of 5.288 – 5.428 GHz. Thus, ZMO forms LTCC composites with TiO2 showing its applicability in RF and MW devices.