A Schottky defect in ZrO_2 would consist of: [a] One Zr vacancy and two O vacanc

Question

A Schottky defect in ZrO_2 would consist of: [a] One Zr vacancy and two O vacancies [b] Two Zr vacancies and one O vacancy [c] One Zr vacancy and one Zr interstitial [d] Two Zr vacancies and two Zr interstitials [e] None of the above Diffusion involving a heat treatment that is used to transport impurity atoms farther into the substrate and to form an oxide layer on the surface in an oxidizing environment is known as: [a] Predeposition diffusion [b] Postdeposition diffusion [c] Drive-in diffusion [d] Interstitial diffusion [e] Vacancy diffusion It is observed that after a certain amount of impurities are added to a metal, a material with a different crystal structure than the original metal's crystal structure forms. This structure is known as: [a] Substitutional solid solution [b] Interstitial solid solution [c] Interstitial transformation [d] Secondary phase

Explanation / Answer

A1. The answer is (a) one Zr vacancy and two O vacancies.

Explanation: Schottky defects belong to the category of Intrinsic point defects. A schottky defect consists of charge balancing cation and anion vacancies. Zr has a charge of +4, whereas, O has a charge of -2 in ZrO2. Thus Schottky defect in ZrO2 would consist of one Zr and two O vacancies.

A2. The answer is (e) Vacancy diffusion.

Explanation: In vacancy diffusion, the impurity atom jumps from one lattice site to another and is responsible for the movement vacancy. Thus, when the vacancy moves to the surface, oxide layer easily occupies the vacant site on the surface.

A3. The answer is (b) interstitial solid solution.

Explanation: In the interstitial solid solution, distorted crystal lattice is formed and that is different from the original.

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