Electroceramic based on Ca3-xBaxZrSi2O9 solid solutions for microwave and radiofrequency application

Abstract

The structural and dielectric characterization of the Ca3ZrSi2O9 (CZS) ceramic compound and the Ca3-xBaxZrSi2O9 (BaCZS) solid solution were investigated for their application in radiofrequency (RF) and microwave (MW) antenna devices. All of the samples were synthesized using the solid-state route. The structural characterization of the samples was performed by X-ray powder diffraction pattern. Infrared and Raman spectroscopy were used to correlate the absorption bands of the main chemical bonds in the materials. Scanning electron microscopy was used to examine the surface and microstructure of the samples. Dielectric properties at MW and RF ranges were analyzed using the Hakki-Coleman and Silva-Fernandes-Sombra methods. The CZS electrocemaric showed a dielectric relative permittivity (ε’) of 10.96, a dielectric loss (tan δ) of 8.28 × 10−4 at 10.20 GHz, and a resonant frequency temperature coefficient (τf) of −44.30 ppm °C−1. The influence of Ba ions on the CZS phase was evaluated using molar ratio variations (x = 0.15, 0.30, and 0.45), denotated as Ca2.85Ba0.15ZrSi2O9, (0.15BaCZS), Ca2.70Ba0.30ZrSi2O9, (0.30BaCZS), and Ca2.55Ba0.45ZrSi2O9 (0.45BaCZS), respectively. Among these samples, 0.45BaCZS showed a τƒ of approximately zero (−5.78 ppm °C−1), demonstrating an improvement in the material with the addition of Ba. Preliminary tests at MW and RF showed that the permittivity values and dielectric losses varied accordingly with the increase in the proportion of barium, as well as τƒ. For the dielectric resonator antenna (DRA) tests, the samples operated below −10 dB, between 6.57 and 7.7 GHz, behaving like materials used in microwaves devices for C-Band applications.