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The shrinkage behavior of fine zirconia powders containing 2.9 and 7.8 mol% Y2O3 was investigated to clarify the effect of Y2O3 concentration on the initial sintering stage. The shrinkage of powder compact was measured under both conditions of constant rates of heating (CRH) and constant temperatures. CRH measurements revealed that when the Y2O3 concentration of fine zirconia powder increased, the starting temperature of shrinkage shifted to a high temperature. Isothermal shrinkage measurements revealed that the increase in Y2O3 concentration causes the shrinkage rate to decrease. The values of activation energy (Q) and frequency-factor term (β0) of diffusion at initial sintering were estimated by applying the sintering-rate equation to the isothermal shrinkage data. When the Y2O3 concentration increases, both Q and β0 of diffusion increase. It is, therefore, concluded that the increase in Y2O3 concentration of fine zirconia powder decreases the shrinkage rate because of increasing Q of diffusion at the initial stage of sintering.