Microwave dielectric properties of Mg3(VO4)2–xBa3(VO4)2 ceramics for LTCC with near zero temperature coefficient of resonant frequency

The Mg3(VO4)2–xBa3(VO4)2 ceramics have been investigated to obtain a low-temperature co-fired ceramic (LTCC). The highest quality factor (Qf) of approximately 114,000 GHz was obtained when the ceramic with x = 0.2 was sintered at 950 °C for 5 h in air. The temperature coefficient of resonant frequency (τf) of the ceramics sintered at 1025 °C varied from −90 to 60 ppm/°C as the amount of xBa3(VO4)2 increased, and was a near zero value in the sample obtained at x = 0.5 where the dielectric constant (ɛr) and the Qf values were approximately 12 and 55,000 GHz, respectively. In order to reduce the sintering temperatures of Mg3(VO4)2–xBa3(VO4)2 ceramics, the effects of Li2CO3 addition as a sintering aid on the microwave dielectric properties of Mg3(VO4)2–0.5Ba3(VO4)2 ceramics were also characterized in this study. The Li2CO3 addition was effective in reducing the sintering temperature without detrimental effects on the Qf values of the ceramics. One result: the microwave dielectric properties of Mg3(VO4)2–0.5Ba3(VO4)2 with 0.0625 wt%-doped Li2CO3 ceramic, which was sintered at 950 °C for 5 h in air, has a ɛr value of 13, a Qf value of 74,000 GHz, and a τf value of −6 ppm/°C.