Effect of CuO and TiO2 on the sintering temperature and dielectric properties of BaWO4 for LTCC applications

Abstract A series of (1-x) BaWO4-xCuO low-temperature sintered composite ceramics were prepared via co-firing the mixture of BaWO4 and CuO in the first part of this study. The sintering temperature of BaWO4 was decreased from 1150 °C to 950 °C when a little amount of CuO was used as sintering aids. The 0.95BaWO4-0.05CuO sample heated at 950 °C for 4 h had good dielectric performance (Q × f ∼ 31,847 GHz, er ∼ 7.99, τf ∼ −81.7 ppm/°C). However, the negative τf was too large to apply to practice. To solve this problem, the rutile phase TiO2 nano-particle with a large positive temperature coefficient of +450 ppm/°C was added as τf compensator in the second part of the study. TiO2 powders not merely improved the temperature stability, but promoted the grain growth. However, the er value increased from 10.5 to 12.6 and Q×f value decreased slightly as TiO2 content increased from 0.30 to 0.45. The 0.65 (0.95BaWO4-0.05CuO) −0.35TiO2 composite ceramic displayed an optimum performance (Q × f ∼ 22,012 GHz, er ∼ 11.21, τf ∼ −2.9 ppm/°C). Such a sample was chemically compatible with silver, implying that it can be implemented on LTCC applications.