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.