Investigation on the 773 K Isothermal Section of the Er-Ni-Si Ternary Phase Diagram by X-ray Powder Diffraction

Abstract

The isothermal section phase diagram of Er-Ni-Si ternary system at 773 K was created by x-ray powder diffraction (XRD) analysis in this paper. Seventeen known ternary compounds ErNiSi, ErNi₂Si₂, ErNiSi₂, Er₂Ni₃Si₅, ErNiSi₃, Er₃Ni₆Si₂, ErNi₁₀Si₂, Er₃NiSi₂, ErNi₂Si, ErNi₅Si₃, ErNi₄Si, ErNi₆Si₆, Er_33.3Ni_18.7−10.7Si₄₈₋₅₆ (Er₂NiSi₃), Er₃Ni₂Si₄, Er_33.3Ni_8.7−4.7Si₅₈₋₆₂ (Er₄NiSi₇), Er₈Ni₃₁Si₁₁, and Er₅Ni₂Si₃ (unknown structure type, similar to Dy₅Ni₂Si₃) have been testified. A new compound Er₃₇Ni₃Si₆₀ (unknown structure type) has been confirmed by excluding its XRD pattern as a superposition of nearby phase patterns. Part diffraction peaks have obvious movement with the change of Si content in Er₂NiSi₃ solid solution, and more moving directions are not consistent, especially at (002) and (110) planes. At the same time, quasi–binary solid solutions were detected in Er₂Ni_17−xSi_x, ErNi_5−xSi_x, Er₂Ni_7−xSi_x, ErNi_3−xSi_x, ErNi_2−xSi_x, ErNi_−xSi_x, and ErSi_−xNi_x compounds. Other binary compounds of the Er-Ni-Si system do not show any visible solubility of the third element. If the mixture of α-ErSi₂ and β-ErSi₂ phases is regarded as one ErSi₂ phase, the 773 K isothermal section of the phase diagram of Er-Ni-Si system consists of 55 three phase regions and ten solid solution lines.