High thermal stability of the YNbO4 − CaYTiNbO7 composites for radio frequency and microwave applications

Abstract

The present work shows present the dielectric properties of YNO – CYNTO ceramic composites at Radio Frequency (RF) and Microwave (MW) regions. X-ray diffraction showed that the addition of CaTiO3 (CTO) on YNbO4 (YNO) caused the formation of the CaYTiNbO7 (CYNTO) phase. In the RF analysis, a typical universal dielectric response in the frequency of the temperature-dependent conductivity was found; the frequency-dependent AC conductivity at different temperatures indicates that the conduction process is thermally activated. Regarding the values of the temperature coefficient of capacitance (TCC) was observed a change of signal with the increment of CTO. Besides, the activation energies of composites were calculated and demonstrated an increase with addition of the CTO. In the MW range, it was observed that permittivity and dielectric loss enhance with the addition of CTO. Moreover, the addition caused the improvement of the thermal-stability of YNO where τf value for YCT5% was equal to +0.64 ppm.°C−1. The composites were analyzed as antennas presenting a reflection coefficient below - 10 dB at the resonant frequency, realized gain of 5.10–5.45 dBi, bandwidth of 129–355 MHz and radiation efficiency above 95%. The results obtained indicate that YNO – CYNTO system would be interesting candidates in microwave operating devices.