Powder mixtures of AlN and ZrO
2(PSZ), in which the amounts of ZrO
2 content were 6∼70mol%, were hot-pressed at 1200∼2000°C for 30 minutes under a pressure of 20MPa in reducing atmosphere. When the amount of ZrO
2 in the powder mixture was 33mol% (ZrO
2/AlN=1/2), all raw powders of AlN and ZrO
2 completely reacted, giving a good sintered composite material with brilliant golden colour and finely dispersed reacted products of AlON Spinel, α-Al
2O
3 and ZrN. For the systems above 33mol% ZrO
2, excess ZrO
2 (cubic phase) remained as an unreacted material, while below 33mol% ZrO
2 unreacted AlN remained. In the case of the ratio of ZrO
2/AlN=1/2, a good sintered composite material was obtained and its bending strength σ
f, toughness
KIc, Vickers hardness
HV and Youngs modulus
E were 448MPa, 2.72 MN/m
3/2, 15.3GPa, and 354GPa, respectively. ZrN, one of the reaction products, was oxidized by the heat-treatment at 750°C in air and changed to ZrO
2. This oxidation reaction of ZrN to ZrO
2 gave volume expansion of about 27%. The effect of the surface compressive stress and microcracks arising from this volume expansion on the mechanical properties of the sintered body were discussed.
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