Fine terbium carbonate particles were produced using the precipitation reaction between Tb(NO3)3 and Na2CO3 solutions in water, as an easy, cost-effective and simple method. To optimize the method the Taguchi experimental design (TED) method was used to evaluate the optimal values of the parameters influencing the precipitation process i.e. the conecntrations of terbium and carbonate solutions (CTb, CCa), the flow rate at which the cation solution was added to the anion solution (FTb) and the reactor temperature (Temr) which were optimized through an orthogonal array design (OA9). The influence of these factors on the dimensions of the product were quantitavely studied through analysis of variance (ANOVA), and it was found that terbium carbonate particles could be obtained in nano-scale dimensions through controlling CTb and Temr. Next the carbonate salt was subjected to an one-step thermal decomposition treatment, as a precursor, to obtain terbium oxide nanoparticles. Products were studied using X-ray diffraction (XRD), SEM, FT-IR and thermal analysis, and were also evaluated as photocatalysts for the UV-induced degradation of methyl orange (MO).