Influence of atmosphere on phase transitions of praseodymium oxide at high temperature using high temperature X-ray diffraction and thermogravimetry

High temperature X-ray diffraction analysis and thermogravimetric analysis up to 1400°C and 1500°C, respectively were used to examine the resulting phases and lattice parameters of praseodymium oxide in situ in N₂ and O₂ atmosphere. In N₂ (log(pO₂/Pa)=1.5), a superlattice reflection of the C-type rare earth structure was detected between 700°C and 1000°C before the decomposition of the defect fluorite into A-type rare earth structure. On the other hand, In O₂ (log(pO₂/Pa)=5.0), such a superlattice reflection was not observed. At the phase transition from defect fluorite (PrO_X) to A-type rare earth structure (Pr₂O₃) for the powder sample on the Pt plate heater, no selective orientation occurred for the Pr₂O₃ in N₂ (above 900°C), however, a strong c-axis orientation of Pr₂O₃ perpendicular to the Pt plate was observed in O₂ (above 1400°C). Such results have not been previously reported. Thermogravimetric analysis helped to identify intermediate phases.