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

A series of (1- x) BaWO 4 - x CuO low-temperature sintered composite ceramics were prepared via co-firing the mixture of BaWO 4 and CuO in the first part of this study. The sintering temperature of BaWO 4 was decreased from 1150 °C to 950 °C when a little amount of CuO was used as sintering aids. The 0.95BaWO 4 -0.05CuO sample heated at 950 °C for 4 h had good dielectric performance (Q × f ~ 31,847 GHz, ε r ~ 7.99, τ f ~ −81.7 ppm/°C). However, the negative τ f was too large to apply to practice. To solve this problem, the rutile phase TiO 2 nano-particle with a large positive temperature coefficient of +450 ppm/°C was added as τ f compensator in the second part of the study. TiO 2 powders not merely improved the temperature stability, but promoted the grain growth. However, the ε r value increased from 10.5 to 12.6 and Q×f value decreased slightly as TiO 2 content increased from 0.30 to 0.45. The 0.65 (0.95BaWO 4 -0.05CuO) −0.35TiO 2 composite ceramic displayed an optimum performance (Q × f ~ 22,012 GHz, ε r ~ 11.21, τ f ~ −2.9 ppm/°C). Such a sample was chemically compatible with silver, implying that it can be implemented on LTCC applications. [ABSTRACT FROM AUTHOR]