Experimental Investigation of Isothermal Section in the La–Co–Ni System at 723 K

Abstract

The isothermal section of the La–Co–Ni ternary system at 723 K has been constructed in this work by using X-ray diffraction (XRD), scanning electron microscopy, and energy dispersion spectroscopy techniques (SEM-EDS). The experimental results show no existence of ternary compounds at 723 K. The isothermal section consists of 16 two-phase regions and 8 three-phase regions. La3Co and La3Ni, La2Co3 and La2Ni3, La2Co7 and La2Ni7, and LaCo5 and LaNi5 form a continuous solid solution. The ternary solid solubility of Ni in LaCo13 phase and La2Co1.7 phase was determined to be 15.61 at.% and 9.61 at.%, respectively. The solid solubility of Co in the LaNi3, La7Ni3, and LaNi phases was 18.07 at.%, 5.62 at.%, and 8.49 at.%, respectively. The present experimental results are important for the design of La(Fe,Si)13-based magnetic refrigeration materials.