The effects of different annealing conditions on the phase formation with NaZn13 structure were investigated in La(Fe1–xCox)11.9Si1.1 (x=0.068) compounds. It was found that the 1:13 phase was not formed directly from the melt upon cooling but via a peritectic reaction between the pro-peritectic γ-Fe and the La-rich phase. Annealing temperature was very important for the formation of 1:13 phase. Ice water was confirmed to be a preferable quenching medium. La(Fe1–xCox)11.9Si1.1 (x=0.068) compounds with almost single 1:13 phase were obtained at 1473 K after 15 d.
