鐵氧磁體與低溫共燒陶瓷之燒結性質

Abstract

The co-firing behaviour of Ni-Cu-Zn ferrite, LTCC, and Ag has been investigated in the present study. Various amounts of ferrite, LTCC, and Ag powders are mixed and sintered at different temperatures. The interactions between these materials are observed. Laminated specimens composing of ferrite, LTCC, and Ag layers are also prepared by sintering in air or N2. The magnetic properties of the samples are measured by superconducting quantum interference device magnetometer (SQUID) and impedance analyzer. X-ray diffraction is used for the phase identification. The material distribution is investigated by electron probe X-Ray micro-analyzer (EPMA). The addition of bismuth oxide enhances the densification and the grain growth of ferrite. An addition of 0.4 wt% bismuth oxide in ferrite leads to a high permeability. The change of Fe2+ to Fe3+ in ferrite is intrigued by the presence of LTCC and further promoted by the addition of silver. Such oxidation is also enhanced with the increase of the sintering temperature. The oxidation of ferrite and the presence of the α-Fe2O3 seriously degrade the saturation magnetization. A new glass phase is formed during the cofiring of ferrite, LTCC, and silver in air. This glassy phase flows at elevated temperature and affects the diffusion of the material in the samples. When the samples are sintered in N2, copper and silver form a solid solution, which also becomes a liquid phase at high temperature. The Ag-Cu liquid flows toward the ferrite layer and results in the dispersion of silver particles within ferrite in the laminated specimens.