Slip Casting and Thermoelectric Property of CrSi₂

Slip casting is one of the techniques being used to produce ceramics, siliside and carbide preformings with a complex shape. In this investigation, the effects of iron, which contaminates pulverized CrSi2, on the relationship between slip viscosity and pH, the density of the green state, and the thermoelectric property of the sintered CrSi2 have been examined. The results obtained are as follows. The iron content in CrSi2 powder increases linearly with increasing ball-milling duration. After the milling duration of 8.85×105 s, 2.3 mass% of Fe is introduced to the powder with an average particle size of 1.05 μm. The slip viscosity increases and the apparent density of the green sample decreases with the iron content. However, since the iron acts as a sintering accelerator, the density of sintered CrSi2 is increased. The thermoelectric power α, the electrical resistivity ρ and power factor α2⁄ρ of the sintered CrSi2 are about 21%, 30% and 11% lower than those of high purity one at room temperature, respectively. At the temperature difference of 800 K, however, the effective maximum power of the CrSi2, is only a few per cent lower than that of the high purity one and is independent of the iron content in the CrSi2 powder. Therefore, whenever using the slip casting technique, it is not necessary to remove the contaminating iron from the CrSi2 powder, and CrSi2 thermoelectric materials can easily be produced. As an application of the technique, trial products of the sintered CrSi2 caps with straight and complex shapes have been made.