Fig. 3(c) shows the XRD pattern of the products of the sample containing 40% excess Mg and B2O3 which was ball milled for 7.5 h and then subjected to VCS. The XRD pattern indicates that ZrB2 was produced with the formation of minor phase, Mg3B2O6. Comparing this XRD pattern with that given in Fig. 3(b), it can be inferred from the relative peak heights of the products that the amount of Mg3B2O6 increased, which is in accord with the excess usage of Mg and B2O3. The peaks of residual ZrO2 are not visible in this pattern; probably due to high amount of unreacted excess reactants. When this product was subjected to leaching, it was inferred from the XRD pattern given in Fig. 3(d) that although a great amount of ZrO2 was reduced to ZrB2 as compared to Fig. 1(b), a very small amount of ZrO2 still remained unreacted. It is also seen in this pattern that Mg3B2O6 could not be removed from the final product.