What is the Difference Between Zinc Blende and Wurtzite

Zinc blende and wurtzite are both crystal structures found in compounds like zinc sulphide (ZnS). These structures play important roles in various fields, including materials science and semiconductor technology.

What is the difference between zinc blende and wurtzite? When considering their crystal structures, zinc blende has a cube-like arrangement, while wurtzite has a hexagonal base with a specific stacking pattern.

Key Areas Covered

1. What is Zinc Blende 
      – Definition, Features, Structure  
2. What is Wurtzite
      – Definition, Features, Structure 
3. Similarities Between Zinc Blende and Wurtzite
      – Outline of Common Features
4. Difference Between Zinc Blende and Wurtzite
      – Comparison of Key Differences
5. FAQ: Zinc Blende and Wurtzite
      – Answers to Frequently Asked Questions

Key Terms

Zinc Blende, Wurtzite, Zinc Sulphide

What is Zinc Blende

Zinc blende is a crystal structure formed by zinc sulphide (ZnS). It is also called sphalerite. It takes various colours, from yellow to black, depending on the impurities present within. Zinc blende is the most stable form of zinc sulphide. This compound is ionic. Zinc readily loses two electrons (2+) to achieve a stable electron configuration, while sulfur gains two electrons (2-) to fill its outer shell.  Hence, zinc sulphide is formed by the electrostatic attraction between the two opposite ions.

Zinc blende adopts a face-centered cubic (FCC) lattice. Here, sulfur ions occupy the corners and centers of each cube face, creating a network of tetrahedral holes. Half of these holes are then filled with zinc ions, leading to a tetrahedral coordination geometry around both Zn and S. This arrangement maximizes electrostatic attraction and packing efficiency.

Zinc blende can conduct electricity under certain conditions, making it a good semiconductor. This compound is, therefore, used in solar cells, photodetectors, and transistors.

When excited by certain types of energy (like ultraviolet light), zinc blende can absorb energy and then re-emit it as visible light. This phenomenon, known as luminescence, is used in cathode-ray tubes and electroluminescent displays.

What is Wurtzite

Wurtzite is a form of zinc sulphide having a hexagonal crystal structure, unlike zinc blende. This is like a hexagonal base formed by sulfur atoms. Zinc ions then occupy half of the tetrahedral voids within this structure but in a specific stacking pattern. This unique arrangement, denoted as ABAB…, creates a layered effect, distinct from the cubic distribution of zinc blende.

Wurtzite also conducts electricity under certain conditions, which makes it a semiconductor. Its conductivity is regulated by doping, where some zinc atoms are replaced by other elements. This feature is useful in transistors and other electronic components. Wurtzite is piezoelectric. This means that when subjected to mechanical stress, it generates electricity. This makes it valuable in pressure sensors and microelectromechanical systems.

When exposed to specific energy sources, this compound emits light; hence, this material is studied for the development of light-emitting diodes.

Similarities Between Zinc Blende and Wurtzite

1. Both zinc blende and wurtzite have the same chemical formula, ZnS.
2. The presence of ionic bonds can be seen in both structures.
3. Both have semiconductor properties.

Difference Between Zinc Blende and Wurtzite

Definition

• Zinc blende is a crystal structure characterized by a cubic arrangement of atoms, while wurtzite is a crystal structure characterized by a hexagonal arrangement of atoms.

Crystal Structure  

• Zinc blende’s crystal structure is a cubic lattice, while wurtzite’s crystal structure is a hexagonal lattice.

Stability

• Zinc blende is thermodynamically more stable than wurtzite under normal conditions.

Atoms

• Wurtzite packs atoms slightly less efficiently compared to zinc blende because of the hexagonal arrangement.

Piezoelectricity

• Wurtzite exhibits piezoelectricity while zinc blende lacks that property.

Conclusion

Zinc blende (sphalerite) and wurtzite are two crystal structures. Both share the same chemical formula and some properties like being semiconductors. However, the main difference between zinc blende and wurtzite is their crystal structures. Zinc blende has a cube-like arrangement, while wurtzite has a hexagonal base with a specific stacking pattern.

FAQ: Zinc Blende and Wurtzite

1. Is wurtzite a piezoelectric?

Yes, wurtzite is a piezoelectric material. The piezoelectric effect refers to the ability of certain crystals to generate an electric potential (voltage) when mechanical stress is applied.

2. What type of ore is zinc blende?

Zinc blende is a type of sulfide ore, which means it’s a mineral that contains zinc in the form of a sulfide compound.

3. Why is zinc blende more stable than wurtzite?

Zinc Blende’s structure has a cubic close packing (CCP) arrangement. But the wurtzite structure has a hexagonal close packing (HCP) arrangement. This is why zinc blende is more stable than wurtzite.

4. Is wurtzite hexagonal?

Yes, wurtzite is a hexagonal crystal structure. In the wurtzite structure, the atoms are arranged in a hexagonal lattice with alternating layers of atoms.

5. Is wurtzite a rare mineral?

Wurtzite is a rare and unstable material. It is a high-temperature polymorph of the more common mineral sphalerite.

Reference:

1. “Sphalerite.” Wikipedia. Wikipedia Foundation.
2. “Wurtzite.” Wikipedia. Wikipedia Foundation.

Image Courtesy:

1. “Zincblende structure” By Catvector – Own work (CC BY-SA 4.0) via Commons Wikimedia
2. “Wurtzite cell GIF” By Physicoro – (CC BY-SA 3.0) via Commons Wikimedia