The effects of sintering time and temperature on the dimensional change and magnetic properties have been observed in barium ferrite permanent magnet. The starting material was a commerical calcined barium ferrite powder containing small amounts of $SiO_2$ and PbO. The specimens of cylindrical shape...
The effects of sintering time and temperature on the dimensional change and magnetic properties have been observed in barium ferrite permanent magnet. The starting material was a commerical calcined barium ferrite powder containing small amounts of $SiO_2$ and PbO. The specimens of cylindrical shape were sintered in air at $1100\,^\circ\!C,\; 1150\,^\circ\!C,\; 1200\,^\circ\!C,\; 1250\,^\circ\!C$, and $1300\,^\circ\!C$ for 30 minutes, 1 hour, 2 hours, and 4 hours. The axial and radial dimensional changes under these sintering conditions were accurately measured. Density was observed to increase with progress of sintering, but at $1300\,^\circ\!C$ it decreases with increasing sintering time. As sintering progressed, remanence, coercive force, and(BH) max. initially increased with sintering temperature and time. But above $1250\,^\circ\!C$ these properties drop sharply with increasing sintering time and temperature. This effect is attributed to the formation of new phases that could not be clearly identified by Xray diffraction.
The effects of sintering time and temperature on the dimensional change and magnetic properties have been observed in barium ferrite permanent magnet. The starting material was a commerical calcined barium ferrite powder containing small amounts of $SiO_2$ and PbO. The specimens of cylindrical shape were sintered in air at $1100\,^\circ\!C,\; 1150\,^\circ\!C,\; 1200\,^\circ\!C,\; 1250\,^\circ\!C$, and $1300\,^\circ\!C$ for 30 minutes, 1 hour, 2 hours, and 4 hours. The axial and radial dimensional changes under these sintering conditions were accurately measured. Density was observed to increase with progress of sintering, but at $1300\,^\circ\!C$ it decreases with increasing sintering time. As sintering progressed, remanence, coercive force, and(BH) max. initially increased with sintering temperature and time. But above $1250\,^\circ\!C$ these properties drop sharply with increasing sintering time and temperature. This effect is attributed to the formation of new phases that could not be clearly identified by Xray diffraction.
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