Doping MgO with Al3+ produces the solid solution Mg1−xAlxO1−x∕2
CHEMISTRY · Single correct · CBSE · Chemistry · d- and f-Block Elements · d- and f-Block Elements
Problem
Doping MgO with Al3+ produces the solid solution Mg1−xAlxO1−x∕2. Which statement best explains why cation vacancies form during this substitution?
(a) Because Al3+ is smaller than Mg2+, extra space appears in the lattice and neighbouring Mg2+ ions shift out of their sites, creating vacancies.
(b) The higher charge of Al3+ requires removal of some Mg2+ ions so the crystal remains electrically neutral.
(c) The substitution increases the lattice energy, pushing some Mg2+ ions into interstitial positions and leaving their original sites vacant.
(d) To preserve neutrality, the lattice forms O2− vacancies instead; the resulting distortion is observed as cation vacancies.