Low Temperature Sintering Characteristics of Hot Press Sintered SrFe 12 O 19 Ferrites for Use in Microwave LTCC Circulators

Abstract The SrFe 12 O 19 ferrites with different amounts of Bi 2 O 3 additive were prepared by a hot press sintering process at a low fired temperature of 870 °C in order to be compatible to the LTCC (low temperature co-fired ceramics) technology, and their low temperature sintering characteristics were investigated, including the crystal phase composition, sintering density, porosity, and magnetic properties. Results show that the addition of Bi 2 O 3 promotes the formation of SrFe 12 O 19 phase structure and increases the sintering compactness and magnetic properties of the ferrites fabricated at 870 °C. The ferrites with Bi 2 O 3 content from 2 wt% to 4 wt% exhibit a compact microstructure with sintering density higher than 4.65 g·cm −3 and porosity lower than 10%, which contributes to the enhanced saturation magnetization M s and intrinsic coercivity H ci above 252.4 kA·m −1 and 312.9 kA·m −1 , respectively. Moreover, the potentiality of the SrFe 12 O 19 ferrites for use in microwave LTCC circulators was also discussed based on their low temperature sintering characteristics.