Thermoelectric properties and thermal stress simulation of pressureless sintered SiC/AlN ceramic composites at high temperatures

Abstract

This paper provides a detailed study of the thermoelectric properties of SiC/AlN composites in a wide temperature range. Evaluation of thermal stress durability of the composites was simulated and analyzed. SiC/AlN composites with 0–30 wt% of AlN were produced by the pressureless sintering method. Phase analysis, densification, and microstructure of the obtained composites were inspected. SiC/AlN ceramics had a porous structure with porosity ranging from 23.77% to 31.74%. Complete 2Hss SiC/AlN solid solution was formed and its content increased with the increment of AlN wt%. Addition of AlN to SiC ceramics gave a harmonic structure with elongated grains morphology. Electrical resistivity and thermoelectric properties of the investigated ceramics were evaluated in the temperature range of 25–1000 K. The results were essentially dependent on AlN content, microstructure and temperature. SiC/AlN composites gave identical behavior of the p-type semiconductors with outstanding thermoelectric properties at high temperatures. The lowest electrical resistivity of 1.5 × 105 µOhm × cm and the highest Seebeck coefficient of 370 µ V/K were recorded for 30% AlN composite at 1000 K. Figure of merit (ZT) increased dramatically with increasing the AlN content. 30% AlN composites recorded ZT value 130 times larger than that of the 0% AlN composite. Thermoelectric power factor was markedly enhanced by increasing AlN wt%. Thermal stress analysis of the different ceramics was simulated by finite element method up to a temperature of 1773 K. SiC/AlN composites gave splendid thermal stress durability with uniform transition and distribution of heat. SiC/AlN composites are strongly nominated to be used effectively in thermoelectric power generation and high-temperature applications.