New LTCC-hexaferrites by using reaction bonded glass ceramics

Hexaferrites are usually prepared according to the standard mixed oxide method with high sintering temperatures of up to 1350 °C, which are not suitable for low temperature cofired ceramics (LTCC) technology. In this work, the sintering temperature of BaFe12O19 was reduced to 900 °C by the development of reaction-bonded glass ceramics systems for LTCC-hexaferrites. Low amounts of reactive glasses (<7 vol.%) based on boron and zinc oxide were used as sintering additives to achieve full densification at 900 °C. The influence of variation in glass–ceramics compositions, different processing parameters, advanced powder preparation by using high-energy milling and the calcination temperature on achieving high-μ ferrites at 900 °C was studied. The magnetic properties of these LTCC-hexaferrites were characterized by a coaxial airline method and impedance measurements in the frequency range of 0.1–10 GHz. The influence of phase composition and microstructure on magnetic properties was also discussed.