Sm–Sm2Se3 phase diagram and properties of phases

Abstract

A Sm–Sm2Se3 phase diagram has been studied from 1000 K until melting. This system forms three congruently melting compounds: SmSe (ST NaCl, a = 0.6200 nm, T_m = (2400 ± 50) K, and H = 2750 MPa), Sm₃Se₄ (ST Th₃P₄, a = 0.8925 nm, T_m = (2250 ± 30) K, and H = 3350 MPa), and Sm₂Se₃ (ST Th₃P₄, a = 0.8815 nm, T_m = (2150 ± 40) K, and H = 5300 MPa). There are eutectics between Sm and SmSe phases and between SmSe and Sm₃Se₄ phases at 2.5 at % Se, 1300 K and at 54.5 at % Se, 2100 K, respectively. Within the extent of Sm₂₊ Sm₂³⁺ Se4–Sm₂³⁺Se₃ solid solution (ST Th₃P₄), the experimentally determined percentages of Sm₂₊ ions correspond with the values calculated from the formula compositions of samples. The bandgap width for SmSe_1.45 and SmSe_1.48 phases is ΔE = (1.90 ± 0.05) eV.