Effect of temperature and atmosphere on thermolysis of Ce1-xPrx(HCOO)3 precursor for obtaining a palette of pigments based on praseodymium-doped ceria Ce1-xPrxO2

Abstract

For the first time, the possibility of obtaining nanostructured Ce_1-xPr_xO₂ oxides by the precursor method using mixed Ce_1-хPr_х(HCOO)₃ (0 ≤ x ≤ 1) formates as a precursor was demonstrated. Thermal decomposition of precursors upon heating in air and inert atmosphere is a pseudomorphic process, i.e. the three-dimensional architecture of the crystalline aggregates of the precursor is inherited by the product of its thermolysis. For the first time, the patterns of formation of the morphology, composition, properties and nature of oxides formed as a result of thermal decomposition of Ce_1-хPr_х(HCOO)₃ in an inert helium atmosphere, where both the composition of the precursor and the temperature of its heating are of great importance, have been revealed. The charge transfer band (O²⁻→Pr⁴⁺) determines the presence of red and red-brown coloration in Ce_1-xPr_xO₂ powders. The reducing atmosphere resulting from the decomposition of the organic component of the precursor (HCOO⁻) to form CO and H₂ causes a decrease in the Pr⁴⁺/Pr³⁺ ratio in the Ce_1-xPr_xO₂ oxides, which greatly affects their color characteristics. The Ce_1-xPr_xO₂ fluorite structure is retained for the composition with x = 0.5, and at higher praseodymium concentrations, other oxides are formed. Thus, the products of thermolysis of Ce_0.25Pr_0.75(HCOO)₃ and Pr(HCOO)₃ formates are the (Ce_0.25Pr_0.75)₂O₃ oxide with the cubic structure Ce₂O₃ and Pr₂O₃, the powders of which have a yellow-green and yellow color, respectively. The following methods were used to describe the properties of the obtained samples: X-ray diffraction, SEM and EDX, Raman spectroscopy, excitation and luminescence spectra, UV–Vis–NIR spectra, and the electron density functional method.