The rare earth carbonates, M2(CO3)3·xH2O, of Y(III), Ce(III), Nd(III), Sm(III), Gd(III) and Yb(III) have been synthesized by a novel synthetic method involving the reaction of aqueous solutions of the Y(III), Ce(III), Nd(III), Sm(III), Gd(III) and Yb(III) acetate salts with urea at ~90-95 oC. A study of the IR absorption spectra (4000-400 cm- 1) of the formed products clearly indicates the absence of bands due to urea and shows the characteristic bands of carbonate ion. A general mechanism describing the formation of Y(III), Ce(III), Nd(III), Sm(III), Gd(III) and Yb(III) carbonates, M2(CO3)3·xH2O, is suggested.