Microwave dielectric polymer-ceramics sintered at near room-temperature with moisture-proof ability

(1-x)H3BO3-xPE (x = 0.0-0.5) microwave dielectric polymer-ceramics (composite ceramics) with ultra-low sintering temperatures (60-110 degrees C) were prepared via the traditional solid-state method to improve the moisture-proof ability of H3BO3 matrix ceramics. X-ray diffraction (XRD), back-scattered scanning electron microscopy (EDS-SEM), and Raman spectroscopy confirmed that H3BO3 and PE could coexist without intermediate phases. As the x value increased, the dielectric Q value and resonant frequency (Q x integral) decreased from 116,000 GHz (at 15.0 GHz) to 37,000 GHz (at 16.3 GHz), the relative permittivity (epsilon r) varied between 2.83 and 2.14, and the temperature coefficient of the resonant frequency (tau integral) shifted from -147 ppm/degrees C to +27 ppm/degrees C in the (1-x)H3BO3-xPE (0.0 < x < 0.5) microwave ceramics at their optimal sintering temperatures. A near-zero tau integral value (+9 ppm/degrees C) was obtained in the 0.7H3BO3-0.3 PE composite, which simultaneously exhibited an epsilon r value of -2.38 and a Q x integral value of -46,000 GHz (at 15.7 GHz) after sintering at 100 degrees C for 1 h. Interestingly, through the hydrolysis experiment (24-384 h), the Q x integral values of the 0.7H3BO3-0.3 PE and/or 0.6H3BO3-0.4 PE polymer-ceramics were basically maintained at approximately 35,000-40,000 GHz. These results showed that the novel (1-x)H3BO3-xPE polymer-ceramics should be the potential candidates for ultra-low temperature cofired ceramic (ULTCC) technology.