59.
Various sialon materials have been prepared by pressureless sintering at 1775 and 1825 °C using Y
2O
3 and/or Ce0
2 as sintering aids. Constant molar amounts of the oxide mixtures were added in the ratios Y
2O
3/CeO
2: 100/0, 75/25, 50/50, 25/75, 0/100 corresponding to 6.0 and 9.25 wt% for the pure Y
2O
3 and pure CeO
2, respectively. Only one of the compositional series reached full density at 1775 °C with cerium replacing yttrium, whereas at 1825 °C all compositional series except one became dense. The samples sintered showed that yttrium but not cerium stabilizes the sialon phase in these ceramics. The dense cerium-sialon ceramics sintered at 1825 °C have as good hardness and indentation fracture toughness as the corresponding yttrium-sialon ceramics, or even higher for the sialon type of materials. For the mixed - sialon materials the hardness decreased as the amount of a sialon phase decreased by increasing cerium-doping.
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