Four ferritic spheroidal graphite (SG) cast irons (3.4C-3.9Si, 3.5C-2.7Si, 3.5C-2.0Si, and 2.0C-2.1Si, in wt pct) were chosen to study the eutectic cell morphology and the related tensile embrittlement. For the three test materials with high carbon concentration, the results indicate that the average eutectic cell wall size and the amount of cell wall inclusions decrease with decreasing silicon concentration. Compared to the test material with 3.5C-2.0Si, which has many inclusions dispersed in the ferrite matrix, the one with 2.0C-2.1Si shows larger average eutectic cell wall size and larger degree of inclusion clustering in the cell walls. Tensile embrittlement may occur in two temperature ranges, namely, the intermediate low-temperature range at the end of the upper elongation shelf and the intermediate high-temperature range of around 400 ЊC. In both cases, the brittle cracks are initiated preferentially at the inclusion clusters in the eutectic cell wall region. Hence, the two tensile embrittlements occur only for the materials with a larger degree of inclusion clustering in the eutectic cell walls.

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To co-fire with commercial LTCC (Low Temperature Co-fired Ceramic) materials at 850oC ~ 880 oC, different contents of B2O3 were added to the Bi2O3-ZnO-Nb2O5 (BZN) ceramics. The dielectric properties of BZN ceramics sintered at low temperatures were studied. According to the test results, the cubic phase of BZN was transformed into orthorhombic in all the test materials. A BiNbO4 phase was formed in test materials with 2 ~ 5 wt% of B2O3 addition. The BiNbO4 phase was inhibited by extra ZnO addition. The phase transformation of cubic BZN was controlled during the synthesis process of cubic and orthorhombic ZnO-Nb2O5 phase with excess ZnO content. The Cubic and orthorhombic phases of BZN could coexist and be sintered densely at 850 oC/2hr.