Acceleration effect of the ternary carbonate of Li/Na/K on the CO₂-absorption rate of lithium zirconate was studied. Potassium carbonate additive in lithium zirconate powder clearly produces the absorption-rate acceleration as a result of the formation of the binary carbonate of Li/K, which melts at around 500°C. The experimental results obtained revealed that the lithium zirconate powder with the ternary carbonate of Li/Na/K (ternary-type lithium zirconate) shows a more accelerated absorption rate at 500°C, and particularly at 450°C, than does the powder with the binary carbonate of Li/K (binary-type lithium zirconate). At 500°C, the reaction-yield range of CO₂ absorption by a ternary-type lithium zirconate, which shows complete melting of the carbonate formed during the reaction, is 2.3times as long as that by a binary-type. Furthermore, even at 450°C, this ternary type has the range of the complete melting, which is as long as that by the binary-type at 500°C, whereas the binary-type does not have the range. The difference of the acceleration effect between the ternary and the binary carbonate was attributed to the difference of the length of this reaction-yield range.