Synthesis and characterisation of lanthanide-based dioxide

Abstract

In the present work, the microstructure and structure of La_0·25Ce_0·52Nd_0·17Pr_0·06(OH)₃ and La_0·25Ce_0·52Nd_0·17Pr_0·06O₂ is obtained from transmission electron microscopy and X-ray diffraction measurements. Space group P6₃/m is assigned to the structure of La_0·25Ce_0·52Nd_0·17Pr_0·06(OH)₃. Lanthanides are assigned to Wyckoff positions 2c. Cell parameters are a = 6·375(5) Å and c = 3·753(5) Å. The thermal decomposition of this compound was studied by differential scanning calorimetry. The process is exothermal with an enthalpy change ΔH° value of −254±10 kJ mol⁻¹. The decomposition kinetics is complex and two global processes with E_a values of 98±4 and 61±2 kJ mol⁻¹ were observed. The product is a lanthanide dioxide. Space group Fm3m is assigned to the La_0·25Ce_0·52Nd_0·17Pr_0·06O₂. Lanthanides are distributed in Wyckoff positions 4a. The cell parameter is a = 5·479(5) Å. Nanopores in the oxide surface are obtained using this method and characterised by STEM measurements.