ULTCC Glass Composites Based on Rutile and Anatase with Cofiring at 400 °C for High Frequency Applications
The article presents the very first materials to the Ultra-Low Temperature Co-fired Ceramic (ULTCC) technology with the sintering temperature of 400 °C. The dielectric composites are based on a rutile and anatase with commercial GO17 sealing glass. In addition to the bulk samples, also the tape casting procedure is introduce to showing its feasibility to co-firing with commercial Ag electrodes at 400 °C. The structural, microstructural, thermal and microwave dielectric properties in the green and sintered samples were investigated. The optimum amount of glass to fabricate substrates was found to be 30 vol.%. The ULTCC substrates with the anatase TiO₂A-30GO17 and rutile TiO₂R-30GO17 were sintered at 400 °C showed a relative permittivity of 9.9 and 15 and a dielectric loss of 0.006 and 0.003, respectively, at the measurement frequency of 9.9 GHz. The temperature dependences of the relative permittivity were +70 and −400 ppm/°C, respectively. Moreover, the coefficients of thermal expansion of the substrates were 7.4 and 8.3 ppm/°C in the measured temperature range of 50–300 °C. A preliminary test to study the feasibility of the anatase TiO₂A-30GO17 for a dual band antenna was performed due its relative stable temperature behavior.