Pr(NO3)(3). 6H(2)O was used as a precursor to produce PrO1.833 at 600 degreesC in an atmosphere of static air. Thermal processes occurred were monitored by means of thermogravimetry, differential thermal analysis and mass spectrometry. IR-spectroscopy and X-ray characterized the intermediates and final solid products. The results showed that, Pr(NO3)(3). 6H(2)O decomposes through ii endothermic weight loss processes. Five dehydration steps occurred at 130, 180, 200, 230 and 250 degreesC, leading to the formation of crystalline nitrate monohydrate. Which decomposes to Pr(NO3)(2) at 340 degreesC. The latter, decomposes to PrO1.833 at 465 degreesC, via four different intermediates PrO(NO3) at 430 degreesC, and nonstoichiometric unstable, PrO0.25(NO3)(2.5) at 362 degreesC; PT(O)(0.5)(NO3)(2) at 382 degreesC and Pr(O)(0.75)(NO3)(1.5) at 400 degreesC. The gaseous decomposition products identified by mass spectroscopy were water vapor and nitrogen oxides (NO, NO2 and N2O5). The activation energy was determined nonisothermally for the thermal processes monitored throughout the decomposition course. The final product PrO1.833 has a surface area of 46.3 m(2)/g.