Download This PaperCrystal Structures of Praseodymium Nitrate Complexes with Urea, Precursors for Solution Combustion Synthesis of Nanoscale Praseodymium Oxides
11 Pages Posted: 13 Apr 2020
Abstract
Abstract. Crystal structures of praseodymium nitrate complexes with urea (Ur), [Pr(Ur) 2 (H 2 O) 2 (NO 3 ) 3 ] and [Pr(Ur) 4 (NO 3 ) 3 ], were studied. The coordination polyhedra of Pr have the basis of a distorted pentagonal bipyramid with axial water or O-coordinated urea molecules, equatorial urea molecules and bidentate cyclic nitrato groups occupying three bifurcated equatorial vertices. These complexes serve as precursors in solution combustion synthesis of nanocrystalline praseodymium oxides. Combustion of [Pr(Ur) 4 (NO 3 ) 3 ] begins at ~330°C and finishes at ~400°C producing basic carbonate. For preparing Pr 6 O 11 and Pr 2 O 3 , further annealing at higher temperature (>460°C and >770°C, respectively) is necessary.
Keywords: Rare-earth nitrates, Urea, Rare-earth oxides, Thermal analysis, X-ray techniques
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