Exploration of impurity migration behavior in the process of lanthanum purification by Czochralski method

•It is proposed for the first time to purify La by Czochralski method.•Equilibrium separation coefficients of impurities were calculated using the liquidus equation.•The relationship between effective separation coefficients of impurities and pulling speeds was calculated by BPS model.•The purity of La can reach more than 99.995 % after purification by Czochralski method. In order to improve the purification efficiency of La, the Czochralski (Cz) method was introduced into the purification of rare earth metal La for the first time in this work. And the migration behavior of Al, Fe and Ni impurity in the process of La purification by Czochralski method was obtained. The equilibrium separation coefficients k0 of Al, Fe and Ni were first calculated by the slope of liquidus. As k0