Phase reaction of ceria in LPS–SiC with Al2O3–Y2O3and AlN–Y2O3additives

Abstract

AbstractDense SiC with addition of CeO2was obtained by liquid phase sintering using different additives (Y2O3, Al2O3) and (Y2O3, AlN). The total amounts of additives (Al2O3+ Y2O3) and (AlN + Y2O3) were fixed at 10 mass.% and 10 vol.%, respectively. Two different molar ratios of Al2O3:Y2O3additives, 1:1 and 5:3, were selected for investigation. Ratios of AlN:Y2O3were selected as 3:2 and 4:1. Influences of both different ratios of Al2O3:Y2O3and AlN:Y2O3and amounts of CeO2on sintering behaviour were investigated. The phase reaction products were identified by X-ray diffraction and microstructures were investigated using scanning electron microscopy with energy dispersive X-ray spectroscopy techniques. In the samples using Al2O3+ Y2O3as sintering additives, the CeO2was dissolved in Y4Al2O9phase during sintering. The oxidation state of Ce4+changed to Ce3+and Ce3+occupies Y3+positions, causing increases in lattice parameters for Y4Al2O9with CeO2content. In samples with AlN + Y2O3as sintering additives, Y10Al2Si3O18and Y2Si3N4O3were formed in the CeO2-free and CeO2containing compositions. During sintering, the CeO2dissolves in oxynitrides via a similar mechanism as in the Y4Al2O9phase.