The effect of B2O3 impurity in the original B powder on the phase formation of MgB2 during the sintering process

The B2O3 impurity in the original B powder affects the sintering process of MgB2. Mg particles and B2O3 impurity accelerate the solid–solid reaction between Mg and B. The B2O3 impurity could not react with Mg particles before Mg melting. Combined with the thermal analysis and phase identification, the influence of the B2O3 impurity in the original B powder on the phase formation of MgB2 during the sintering process was investigated. It is found that how the B2O3 impurity in the original B powder affects the sintering process of MgB2 depends on the reactivity of Mg particles in the original powder. If the Mg particles in the original powder are small and reactive enough, the B2O3 impurity could react with them before Mg melting during the sintering process and accelerate the solid–solid reaction between Mg and B. Otherwise, the B2O3 impurity could not react with Mg particles before Mg melting and depress the solid–solid reaction between Mg and B.