Sintering of α-Al2O3 nanocrystalline ceramic from large α-Al2O3 polycrystalline nanoparticles

Fine nanoparticles (NPs) exhibit higher sintering activity than large ones and are usually desired for sintering of nanocrystalline (NC) ceramics with fine grains. This paper demonstrates that large α-Al2O3 polycrystalline (PC) NPs with a mean particle size of 62 nm show a similar sintering activity as α-Al2O3 single-crystal (SC) NPs with a mean particle size of 16 nm.α-Al2O3 NC ceramics sintered from the 62 nm α-Al2O3 PC NPs and 16 nm α-Al2O3 SC NPs by two-step sintering exhibit a similar mean grain size of about 75 nm and a similar relative density of about 99.5%. It may be because the 62 nm α-Al2O3 PC NPs and 16 nm α-Al2O3 SC NPs have a similar mean grain size of about 19 nm. These results imply that NC ceramics with fine grains may be sintered from large PC NPs with fine grain sizes.