Beta-SiC powder was synthesized by carbothermal reduction of silica contained in rice hull ash, and porous ceramics were fabricated by conventional sintering. Electrical conductivity and Seebeck coefficient were measured as functions of temperature under Ar atmosphere to evaluate their applicability to thermoelectric energy conversion. Thermoelectric properties of beta-SiC ceramics fabricated from rice hull ash were comparable to those fabricated from a commercial high-purity powder.
Composites in the TiN-TiO2 system were fabricated by decomposition and sintering of the TiN particles coated with Ti-alkoxy-derived gel. Non-linear current-voltage (I-V) characteristics was obtained in a suitable composition. Model experiments with TiN/TiO2/TiN (metal-insulator-metal) structure indicated that Poole-Frenkel emission through a thin (0.2 micrometer) insulating TiO2 was a predominating mechanism for the non-linearity. Proper insertion of thin insulating layers into the intergranular regions in metallic solids in composite forms was ...
Porous SiC ceramics fabricated from hollow particles and polycarbosilane (PSC) are promising materials for high-temperature thermoelectric energy conversion. Reaction sintering of PCS-impregnated compacts of SiC hollow particles gave rise to porous microstructures with the hollow shape remaining. The repetition of the PCS-impregnation and sintering process resulted in only a slight increase in density but in a great improvement in thermoelectric properties.
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