Investigation of the composites of epoxy and micro-scale BaTi₄O₉ ceramic powder as the substrate of microwave communication circuit

BaTi₄O₉ (BT4) ceramic was sintered at 1270 °C and ground into fine ceramic powder with average particle size of about 3 μm. After that, the micro-scale BT4 ceramic powder with different concentrations (from 5 to 70 wt%) was mixed with O-Cresol Novolac (OCN) epoxy resin to form flexible epoxy-BT4 composites. The dielectric constant of epoxy-BT4 composites was first measured from 100 kHz to 100 MHz at room temperature by using the “plate method”. The measured dielectric constants of epoxy-BT4 composites were compared with the values predicted by Lichtenecker equation. We would show that the measured results were well fitted with the predicted values. In order to investigate the composites of epoxy and micro-scale BT4 ceramic powder for the application of microwave communication, the dielectric constants of epoxy-BT4 composites were also measured from 1 to 10 GHz at room temperature by using a “square cavity resonator” method. As the measured frequencies were at the range of GHz, the dielectric constants of epoxy-BT4 composites were almost unchanged with the increase of frequency. It conjectured that epoxy-BT4 composites could be used as the flexible substrates to fabricate the microwave filters and antennas.