Low temperature sintering behavior of La-Co substituted M-type strontium hexaferrites for use in microwave LTCC technology

The La-Co substituted Sr1-xLaxFe12-xCoxO19 (x=0-0.5) ferrites with appropriate Bi2O3 additive were prepared by conventional sintering method and microwave sintering method at low sintering temperatures compatible with LTCC (low temperature co-fired ceramics) systems, and their sintering behavior was chiefly investigated, including the crystal structure, saturation magnetization Ms, magnetic anisotropy field Ha, intrinsic coercivity Hci, and Curie temperature TC. Experiment results clearly showed that the pure M-type crystal phase was successfully obtained when the La-Co substitution amount x did not exceed 0.3. However, the single M-type phase structure transformed to multiphase structure with further increased x, where the M-type phase coexisted with the non-magnetic phase such as α-Fe2O3 phase, La2O3 phase, and LaCoO3 phase. Appropriate La-Co substitution improved the Ms (>62 emu/g), Ha (>1400 kA/m), and Hci (>320 kA/m) for the ferrites with x varying from 0.1 to 0.3, but the TC decreased with increasing substitution amount. Moreover, the microwave sintered ferrites could provide larger Hci and similar Ms compared with the conventional sintered ferrites.

Graphical AbstractCurie temperature of the La-Co substituted Sr1-xLaxFe12-x CoxO19 ferrites prepared by different sintering methodsFigure optionsDownload as PowerPoint slide