Highly pure -sialon powders (z=2 and 3) derived from silicon-diimide were sintered by HIP without additives . The sinter ing behavior was compared with that of mixed powders of Si3N4 AN and A2 In synthesized powders , full density was attained after HPing under 160MPa at 1500 (z=3) and 1600 (z=2) for 2h, respectively. These temperatures were found to be 100 to 300 lower than that required to complete the sialon formation in mixed powders. After HlPing at the lowest temperature necessary for

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... densification, little grain growth was observed and maximum hardnesses of 16 .5GPa (z=2) and 15.0GPa (z=3) were obtained. Fracture toughness was 3 to 4MPa•12 by the indentation method . Flexural strength was as low as 250 to 300MPa.