High-temperature oxidation of europium (II) sulfide

Abstract

The process of high-temperature oxidation of EuS in the air was explored in the temperature range of 500-1000°C. The oxidation reaction enthalpy was determined (ΔH 0 exp =-1718.5 kJ/mol). The study of oxidation products allowed to establish the mechanism of EuS oxidation with oxygen. At 500-600°C, EuS is oxidized to a mixture of Eu 3+ -containing compounds (Eu 3 S 4 , Eu 2 O 2 S). In the range of 700-1000°C, only europium sulfate Eu 2 O 2 SO 4 is formed. The structure refinement for Eu 2 O 2 SO 4 was performed by the Rietveld method. The luminescence intensity of europium oxysulfate Eu 2 O 2 SO 4 with characteristic 4f-4f transitions from the 5 D 0 state was investigated as a function of oxidation temperature.

Synthesis of Samarium OxysulfateSm2O2SO4 in the High-Temperature Oxidation Reaction and Its Structural, Thermal and Luminescent Properties

“…The temperature increase to 700 • C leads to a sharp increase in the reaction rate, and the complete oxidation of the sample is reached for one hour. Such behavior differs significantly from the EuS oxidation process [35] where such pronounced rate temperature dependence is not observed. This effect is obviously related to the fact that only one reaction occurs during the Sm 2 O 2 S oxidation, in contrast to the EuS oxidation process, in which several parallel competing processes are realized.…”

“…A sample of Sm 2 O 2 SO 4 for structural analysis was obtained by oxidizing samarium oxysulfide in the air at 900 • C for 10 h. The Rietveld refinement was carried out by using TOPAS 4.2 [50] which accounts the esd's of each point by a special weight scheme. All peaks were indexed by a monoclinic cell (C2/c) with the parameters close to those of Eu 2 O 2 SO 4 [35] and; therefore, the crystal structure of Eu 2 O 2 SO 4 was taken as a starting model for Rietveld refinement. The Eu 3+ site in the Eu 2 O 2 SO 4 structure was considered as occupied by the Sm 3+ ion.…”

“…As it is known from the reported results, the initial material granules, under certain conditions, are able to maintain the original shape and size in the thermal decomposition process [28][29][30]. At the same time, the compounds with the stoichiometric lanthanide ion content attract attention in order to find efficient luminescent materials with low concentration quenching and to investigate specific mechanisms of luminescence quenching in them [31][32][33][34][35][36][37][38][39][40]. At the same time, the consideration of lanthanide-containing materials cannot be restricted only by their luminescent properties.…”

Thermal Stability and Decomposition Products of P-Doped Ferrihydrite

“…3363 and 1622 cm −1 are assigned to the stretching and bending OH vibrations of the lattice and to the adsorbed water, respectively [ 2 , 47 , 49 , 50 , 51 ]. The bands at 974, 1050, and 1123 cm −1 are derived from sulfate–ferrihydrite complexes [ 52 ] and these bands can be associated with symmetric v1 and antisymmetric v3 stretching bands of SO4 tetrahedra [ 53 , 54 ]. This artifact resulting from the presence of residues of the reagents used in the synthesis was observed previously [ 24 ].…”

Structural Features of Y2O2SO4 via DFT Calculations of Electronic and Vibrational Properties

“…As to the Re 2 O 2 SO 4 oxysulfates, the crystal structure of Nd 2 O 2 SO 4 [28] was solved in the non-centrosymmetric (I222) space group and thus this class of compounds can be a candidate for NLO materials. On the other hand, the crystal structure of Sm 2 O 2 SO 4 [29] and Eu 2 O 2 SO 4 [30] was solved in the centrosymmetric (C2/c) space group.…”