Chlorination of Pr2O3 and Pr6O11. Crystal structure, magnetic and spectroscopic properties of praseodymium oxychloride

The reactions of Pr2O3 and Pr6O11 with Cl2(g) were studied thermodynamically and experimentally, and proposed in the systems Pr2O3/Cl2(g) and Pr6O11/Cl2(g). A kinetic analysis was performed on Pr6O11 chlorination, which differs from with other light rare earth oxide chlorinations. The praseodymium oxychlorides obtained by full chlorination of Pr6O11 at 425 °C and 800 °C are different, being well characterized by X-ray diffraction, scanning electron microscopy, magnetic susceptibility measurements and X-ray photoelectron spectroscopy. The crystal structures of the oxychlorides were refined with the Rietveld method. The comparison between the theoretical magnetic moment of Pr3+ and the estimated magnetic moment in the praseodymium oxychloride obtained at 425 °C revealed the presence of Pr3+ and Pr4+, whereas no significant difference was observed between the theoretical and the experimental values of Pr3+ obtained for the praseodymium oxychloride prepared at 800 °C. These observations are consistent with the analyses in the X-ray photoelectron spectra for both oxychlorides. Finally, a general formula of PrO1+xCl is proposed for the oxychlorides synthesized at T < 800 °C.