<p>The study of the physicochemical properties of rare-earth electroslag systems is fundamental and crucial for the preparation of reduced activated ferritic/martensitic (RAFM) steel. The effects of Y₂O₃ and CaO/Al₂O₃ (C/A) on the melting temperature, viscosity, and electrical conductivity of the slag were investigated in this paper. The results indicated that the melting temperature initially decreased and then increased as the Y₂O₃ content rose from 3&#xa0;wt pct to 15&#xa0;wt pct. The changes of high-melting phases, CaYAlO₄ and MgAl₂O₄, were the fundamental cause of the variation in the melting temperature. The slag exhibited the lowest melting temperature and viscosity, when the Y₂O₃ content was 9&#xa0;wt pct. The melting temperature decreased with an increase in C/A, and a moderate increase in C/A could improve the flowability of the slag. The viscosity of slag exhibited a continuous reduction as the C/A ratio increased from 0.9 to 1.1. When the Y₂O₃ content was 9&#xa0;wt pct and the C/A ratio was 1.0, the activation energy for slag electrical conductivity was minimized at 54.62 kJ·mol⁻¹, resulting in the lowest energy required for the migration of conductive ions and the highest electrical conductivity. Raman spectroscopy results indicated that the transformation of Q⁰_Al, Q¹_Al, Q²_Al, Q³_Al, and Q⁴ structural units in the slag, which led to changes in the degree of polymerization, was the primary factor influencing the viscosity of the slag.</p>