An investigation on the thermal and microstructural properties of low-cost pressureless sintered silicon nitride (Si3N4) ceramics incorporated with Y2O3-SiO2-MgO

Abstract

Y2O3-SiO2-MgO-incorporated silicon nitride (Si3N4) ceramics were investigated systemically to obtain cost-effective production and the effect of sintering temperature on the microstructure and thermal properties was studied. An alpha-Si3N4 starting powder was used for preparing the samples and sintered under a pressure of one bar nitrogen gas pressure at 1650, 1700, 1750, 1800, and 1850 degrees C for 2 h. The crystallisation behaviour of the ceramics was promoted by sintering temperatures as evidenced by the XRD results. A different secondary phase, melilite (Y2Si3O3N4) formation, was detected using SEM micrographs of the final microstructures of the samples sintered at higher temperatures above 1700 degrees C which had a positive effect on thermal properties. The values of thermal conductivity increased by about 75.5% with increasing sintering temperature. The highest thermal conductivity (53.58 W/(mK)) was achieved with the highest sintering temperature of 1850 degrees C. The results revealed that ternary sintering additives, such as Y2O3-SiO2-MgO, had a potential for low-cost production of Si3N4 ceramics with enhanced thermal properties.