Evaluation of the High-Temperature/High-Efficiency Thermoelectric Device Consisted of Refractory Semiconducting Ceramics

对多孔碳化硅和碳化硼这两种耐火材料的高温热电转换效率进行了研究，得到了以下结果：首先，对于多孔性碳化硅，以实心和中空的碳化硅微粉为原料，采用常规烧结工艺，获得了孔隙率不同、粒度分布呈双峰分布的微结构。材料的热电性能测试表明，多孔碳化硅的单晶基质中弥散着非常细小的气孔，具有较大的热电转换优值。其次，对于碳化硼，通过改变CVD工艺条件制备了具有不同颗粒尺寸和不同晶轴取向程度的恒定组成碳化硼厚膜陶瓷，并对其热电性能进行了研究。研究发现，具有任意晶轴取向的细晶多晶应该具有较高的能量转换效率。

Investigations on the high-temperature thermoelectric conversion efficiency of refractory semiconductors, namely porous SiC and boron carbide were carried out and the following results were obtained.First, for porous SiC,microstructures with various porosities and bimodal grain-size distributions were achieved by normal sintering process employing both solid and hollow fine particles of SiC as starting materials. Measurement of thermoelectric properties of the resultant materials has shown that porous SiC of its single-crystalline matrix dispersed with very fine pores would give large figures of merit for thermoelectric conversion.Second, for boron carbide, thick-film ceramics with constant composition yet with different grain sizes and different degrees of crystal axis orientation were fabricated by varying the CVD conditions, and their thermoelectric characteristics were investigated. It was found that fine-grained polycrystals with random crystal-axis orientation should give high energy conversion efficiency.