Question

If the following point defect is introduced: Mg2+ ions substitute for yttrium ions in Y2O3. Would we add 3 Mg2+ ions,remove 2 Y3+ ions , and would one of the Mg2+ ions go to a interstitial site to conserve the number of crystallographic sites or would there be a vacancy created? What would the Kroger-Vink notation be?

Answer 1

In this case, the more likely scenario is Mg²⁺ will replace the Y³⁺ in the system with one Mg²⁺ going to interstitial sites.

The size of Mg²⁺ is 86 pm while the size of Y³⁺ is 104 pm. Because of nearly same size, the Mg²⁺ ions are likely to replace the Y³⁺ in the crystal structure. As a consequence, the excess Mg²⁺ is likely to remain in the interstitial site.

For this case, the Kroger-Vink notation can be written as: