Chapter 4, Problem 4.17P

Interpretation Introduction

(a)

Interpretation:

The number of Schottky defects per unit cell is to be determined for the given ZnS sample.

Concept introduction:

In ionic materials, most common defects found is the Schottky defect in which stoichiometric number of cations and anions are missing from the crystal lattice and the electoral neutrality of the crystal is preserved.

The relationship between the theoretical density $\left(\rho \right)$ of an alloy, number of atoms of all the constituent species present in the alloy $\left(n_i\right)$ present in a unit cell and volume of a unit cell $\left(V\right)$ is:

  $\rho =\frac{{\displaystyle \sum n_i\times {\left(\text{A}\text{.M}\right)}_i}}{V\times N_{\text{A}}}$ ....... (1)

Here, ${\left(\text{A}\text{.M}\right)}_i$ is the atomic mass of the species $i$ in the alloy and $N_{\text{A}}$ is the Avogadro's number.

Volume of a unit cell $\left(V\right)$ is calculated using the lattice parameter $\left(a_0\right)$ as:

  $V={\left(a_0\right)}^3$ ....... (2)

Interpretation Introduction

(b)

Interpretation:

The number of Schottky defects per ${\text{cm}}^3$ is to be determined for the given ZnS sample.

Concept introduction:

Number of cells per unit volume of the cell is:

  $\text{Number of unit cells}=\frac{1}{V}$ ....... (3)