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Fully dense aluminum nitride (AlN) ceramics were synthesized by self-propagating high-temperature synthesis (SHS) method using AlN powder as raw material with Y2O3 additive.The sintering behavior was studied at different sintering temperatures and additive contents.The change of phase compositions,secondary phase distribu-tions and grain morphologies during sintering process were investigated.It is shown that fully dense ceramics using AlN powder prepared by SHS method can be obtained when the sintering temperature is above 1830 ℃.Both Y2O3 content and sintering temperature have an important influence on the formation of Y-Al-O phase and grain shape.When Y2O3 content is identified,the grain mor-phology converts from polyhedron into sphere-like shape with the rise of sintering temperature.At a certain sintering temperature,the grain size decreases with the increase in Y2O3 content.The influencing mechanisms of different Y-Al-O secondary phases and sintering temperatures on the grain size and morphology were also discussed based on the experimental results.