Synthesis , Structure and Complex Study of Properties of EuErCuS 3

The crystal structure of the first-synthesized compound EuErCuS3 was determined from X-ray powder diffraction data: orthorhombic crystal system, space group Pnma, structural type Eu2CuS3: a = 10.1005(2) Å, b = 3.91255(4) Å, c = 12.8480(2) Å; V = 507.737(14) Å3, Z = 4, and ρx = 6.266g/cm3. The temperatures and enthalpies of reversible polymorphic transitions and of incongruent melting of the compound were determined by DSC: Tα↔β= 1524 K, ΔНα↔β = 2.3±0.2 kJ∙mol-1;Tβ↔γ = 1575 K, ΔНβ↔γ = 0.7±0.1 kJ∙mol-1;Tγ↔δ=1602 K; ΔНγ↔δ= 1.3±0.1 kJ∙mol-1; and Tm =1740±6 K, ΔНcr=-3.5±0.3 kJ∙mol-1.IR spectra were recorded in the range from 50 to 400 cm-1. The compound was found to be IR-transparent in the range 4000400 cm-1. The compound was characterized by Raman spectroscopy. The observed spectra featured both Raman lines and luminescence. Ab initio calculations of the EuErCuS3 crystal structure and phonon spectrum were performed, the frequencies and types of fundamental modes were determined, and the involvement of constituent ions in the IR and Raman modes was assessed from an analysis of the ab initio displacement vectors. The vibrational spectra were interpreted. EuErCuS3 experiences a ferromagnetic transition at 4.8K. Its microhardness is 2850MPa. The data obtained can serve as the basis for predicting the properties of EuLnCuS3 compounds. Valence states for Eu (2+) and Er (3+) are proved both by XRD and optical methods. Prime Novelty Statement The prime novelty of this research is the complex study of the crystal structure and multifunctional properties of EuErCuS3 multication sulfide. The crystals compound are orthorhombic symmetry which melts incongruently. This compound has a 3 high-temperature polymorphic transitions and is a wide-gap semiconductor which contains the magnetic ion Er 3+ experiencing a lowtemperature ferromagnetic transition. Valence state of Eu 2+ ion is determined via XRD and optical techniques. Ab initio calculations of the EuErCuS3 crystal structure and phonon spectrum were performed, the frequencies and types of fundamental modes were determined, and the involvement of constituent ions in the IR and Raman modes was assessed from an analysis of the ab initio displacement vectors. Prime Novelty Statement