Thermal stability of (Co,Cu)Z-hexaferrite and its compatibility with Ag at 900°C

Z-type hexaferrite with the composition Ba3Co1.4Cu0.6Fe24O41 was studied as a candidate material for low-temperature cofiring technology. The samples were prepared by solid-state reaction at 1250 degrees C and sintered and cosintered with Ag at 900 degrees C. Bi2O3 was used as a sintering additive, which was necessary for the sintering at 900 degrees C. The samples were characterized with X-ray diffraction, electron microscopy, and energy-dispersive spectroscopic analysis. The compatibility study of (Co,Cu)Z-hexaferrite with Ag revealed the degradation of the Z-hexaferrite. However, the present study shows that the (Co,Cu)Z-hexaferrite was compatible with Ag and that the degradation was caused by the thermal instability of (Co,Cu)Z-hexaferrite. The effect of the observed changes in phase composition on the permittivity and permeability of the samples was measured at 10(6)-10(9) Hz.