La2-xRxCuO4 (R: Pr, Y, Nb) polycrystalline ceramics have been prepared by a spark plasma sintering process. Analysis of the microstructure and phase composition shows that pure La2CuO4 ceramics with a high density can be obtained, and no impurity phases appear. All the samples exhibit a metal-semiconductor transition behavior at similar to 750 K, which could be ascribed to the decreasing charge density as a result of loss of oxygen atoms and various conduction mechanisms in these La2CuO4-based ceramics. Our results indicate that the La1.98Y0.02CuO4 ceramics show large thermoelectric power similar to 1.0 x 10(-3) mu W.(m.K-2)(-1), and the evaluated ZT can reach 0.17 at 330 K, which potentially make them useful for thermoelectric applications.