Re-investigation the phase equilibria and thermodynamic assessment of the Nd-Sn binary system

Abstract

The Nd-Sn phase diagram has been investigated within the range of 20–80 at.% Sn using X-ray diffraction (XRD), scanning electron microscope equipped with energy dispersive spectrometer (SEM-EDS), and differential scanning calorimetric (DSC). In addition to the nine known compounds, Nd₅Sn₃, Nd₅Sn₄, Nd₁₁Sn₁₀, NdSn, Nd₃Sn₅, NdSn₂, Nd₃Sn₇, Nd₂Sn₅ and NdSn₃, two reported compounds, Nd₃Sn and Nd₂Sn_3, as well as two new compounds Nd₂Sn and Nd₄Sn₅, have been detected. The formation of Nd₂Sn, Nd₄Sn₅ and Nd₂Sn₃ has been determined as follows: Nd₂Sn forms by peritectoid reaction Nd₃Sn + Nd₅Sn₃ → Nd₂Sn at 1134 °C; Nd₄Sn₅ and Nd₂Sn₃ form by peritectic reaction at 1168 °C and 1146 °C, respectively. Nd₃Sn and Nd₃Sn₅ are only stable at high temperatures, Nd₃Sn forms by a peritectic reaction at 1163 °C and decomposes at 1114 °C, and Nd₃Sn₅ is formed via a peritectic reaction at 1153 °C and decomposes at 1136 °C. Additionally, five invariant reaction temperature have been updated. The Nd-Sn system was modeled using the Calphad approach, incorporating new experimental data along with all other available experimental information. A comprehensive thermodynamic description of the Nd-Sn system has been obtained, and extensive comparisons between calculated and experimental data indicating that almost all adopted experimental and theoretical data are satisfactorily matched.