Co/Ti-substituted M-type hexagonal ferrites for high-frequency multilayer inductors

The sintering behavior, microstructure and permeability of Co/Ti-substituted M-Lype hexagonal ferrites BaCoxTixFe12-2xO19 (1.0,s-;x 14) was studied for applications as multilayer inductors in the high-frequency range up to 2 GHz, Single-phase M-type ter rites were obtained after calcination at 1000 degrees C. The saturation magnetization and coercivity decrease with x and hysteresis measurements illustrate a gradual transition of the anisotropy from uniaxial to planar. Addition of 5 wt% of a BBSZ glass allows densification at 900 degrees C through liquid-phase sintering. The permeability of samples sintered at 900 degrees C increases with the Co/Ti substitution and reaches its maximum of mu' = 16 at 1 MHz at x = 1.3 with a resonance frequency fr >= 1 GHz. Monolithic ferrite multilayer inductors were fabricated with printed Ag coil patterns by co-firing at 900 degrees C. It is shown that Co/Ti-substituted hexagonal M-type ferrite is an excellent material for the high-frequency multilayer inductors. (C) 2015 Elsevier B.V. All rights reserved.