Bismuth titanates candidates for high permittivity LTCC

Bi2O3–TiO2 composites are known to possess attractive microwave dielectric properties. However, producing LTCC analogues with equally promising dielectric properties is problematic. Here, we show that judicious choice of both TiO2 starting powders and dopants can produce composites with excellent properties. Three TiO2 powders were evaluated: 1 μm-anatase, 1 μm-rutile and a nanosized (30 nm) mixture of 75–25 anatase-rutile. The best dielectric properties were obtained by using uncalcined nanosized anatase/rutile with Bi2O3 powder. By doping this Bi2O3–TiO2 powder mixture with 0.112 wt.% CuO dielectric properties of Q × f = 9000 GHz, ɛr = 80 and τf = 0 ppm/K (at 300 K) were obtained at a sintering temperature of 915 °C.