Due to the addition of SrCl2, each Sr2+ ion replaces two Na+ ions, but occupies one Na+ lattice point. Thus, this exchange of Na+ ion by Sr2+ ion makes one cationic vacancy. SrCl2 doped =10−3 mol per 100 mol =10−5 mol per 1 mol ∴ Cation vacancies =10−5 mol per 1 mol =10−5×N0mol−1 =10−5×6.02×1023
Total =6.02×1018 cationic vacancies mol−1