Synthesis of Rare Earth Halides

The resulting materials were prepared by a co-melt and recrystallization method. The starting materials include lithium chloride (LiCl, Alfa Aesar, 99.9%), lithium bromide (LiBr, Alfa Aesar, 99.9%), trivalent rare earth bromides (MBr₃, Alfa Aesar, >99.9%), and metal chlorides (MCl₃, MCl₄, Alfa Aesar, > 99.9%). Raw materials with stoichiometric ratio were directly put and sealed in a quartz tube at ~10 Pa under vacuum. The quartz tube was heated for 4 h to reach 550–650 °C and kept at 650 °C for 12 h. Then the quartz tube was cooled down to 25 °C within 10–48 h.