Nature And Properties of Semi-Conductor Ceramics

Introduction: Semi-conductor ceramics are chemical compounds which are very useful in manufacturing processes as a result of their unique features. This article examines the nature and properties of five semi-conductor ceramics, as well as their uses in the manufacturing sector. Good knowledge of these semi-conductor ceramics will improve their use.

Alumina as a semi-conductor ceramic

Alumina is also known as alumina oxide. It is a semi-conductor ceramic. It is sourced from nature in mineral form. It can also be produced as a synthetic material, through the melting of solid aluminum materials. Alumina is found in various forms, that is why it is said to be amorphous. For example, alumina which is found in crystal form, is known as corundum.

The following table displays the physical, chemical and mechanical properties of alumina.

Table 1: Properties of alumina (aluminum oxide), a semi-conductive ceramic

Uses of Alumina in semi-conductor ceramics: The purposes for which alumina is used is related to its physical, chemical and mechanical characteristics as a semi-conductor ceramic. They are as follows:

• Coating of equipment that are used as furnaces, because alumina has the capacity to withstand very high temperature;

• Used for the production of jewelry

• Used for the production of cutting equipment, because of its hard nature; and

• Used for the production of sand paper which is used to smoothen rough surfaces.

Silicon Nitride as a semi-conductor ceramic

Silicon nitride is a semi-conductor ceramic which is synthetically produced. The production processes which are very expensive and require specialized equipment, are as follows:

   i.         Direct nitridation: In this process, silicon powder and nitrogen gas is burnt at very high temperature conditions to produce silicon nitride.

ii.         Nitridation: Here, the reaction of silicon powder crystals in a bonding process, leads to the production of silicon nitride.

In the same vein, the physical, chemical and mechanical properties of silicon nitride are highlighted in the table below:

Table 2: Properties of Silicon Nitride as a semi-conductor ceramic

Uses of Silicon Nitride in semi-conductor ceramics, include the following:

• It is used in the construction of turbines;

• For the production of equipment and tools which are used in surgical procedures;

• Critically useful in the fabrication of dental and orthopedic implants;

• Useful for the synthesis of microchips;

• Silicon nitride is light weighted and therefore suitable for aircraft manufacture, to facilitate stable movements;

• Used for the formation of ultra-violet light-emitting diodes.

Boron Nitride as a semi-conductor ceramic

Boron nitride is a semi-conductor ceramic which is not commonly found in the environment. It is a rare substance, which is mostly used in its synthetic form, that is, man-made. It is also known as white graphite, because of its close resemblance to granite.

The production cost of Boron Nitride is high and expertise is required to operate the production equipment. High cost of producing synthetic forms of the substance makes it difficult for some industries to access it. This is in spite of the advantages of its use in production activities that require semi-conductor ceramics.

Table 3: Properties of Boron Nitride as a semi-conductor ceramic

Forms of Boron Nitride as a semi-conductor ceramic: Boron Nitride is a peculiar kind of semi-conductor ceramic, because it occurs in three main crystalline forms namely

   i.         H-BN (hexagonal boron nitride – This is soft, lubricating and has low electric conductivity. The shapes generated from this form of boron nitride is usually dense.

ii.         C-BN, which is produced from subjecting H-BN to very high heat. The products of C-BN are very hard; and

   iii.         W-BN, which is formed under lower temperatures than C-BN. W-BN is very useful in the production of hard shapes. It also has a lower density, relative to the other forms of boron nitride.

Uses of boron nitride as a semi-conductor ceramic include the following

• Production of heat sinks.

• Construction of furnaces.

• Synthesis of optic materials.

• Preparation of cosmetics; and

• Fabrication of cutting materials.

Aluminum Nitride as a semi-conductor ceramic

Description: Aluminum nitride is a semi-conductor ceramic. It  is solid aluminum that appears in nitride form. It is a popular choice of semi-conductor ceramics because of its non-toxic nature, as it can be safely used in manufacturing activities. Aluminum nitride is produced synthetically through the combination of aluminum and nitrogen.

Table 4: Properties of aluminum nitride as a semi-conductor ceramic

Uses of aluminum nitride as a semi-conductor ceramic:

• It is used as a heat sink for electrical and electronic applications.

• The substance is deployed for electrical applications in situations where high temperature and heat dissipation is considered a challenge.

• It is combined in the production of plastics and materials made of resin.

• It is used in the production of packaging for electrical equipment.

• Aluminum nitride is also used to produce a thin material known as RF filter, used in mobile phones as an acoustic resonator.

• It is used in the fabrication of microphones.

Silicon Carbide as a semi-conductor ceramic

Silicon carbide is a semi-conductor ceramic which is also known as carborundum. It is found in a natural state in a rare mineral known as moissanite. Tests carried out on samples of silicon carbide showed the presence of isotopes of silicon and carbon. Such elements are also found in star dust which has its origin in space.

Other sources of silicon carbide: Silicon carbide can also be mass produced in crystalline and powdery form. There are two methods of producing synthetic silicon carbide. These are the Lely method and Chemical vapor deposition. Both methods require specialized equipment and a high degree of expertise.

Properties of Silicon Carbide as a semi-conductor ceramic

Uses of Silicon Carbide as a semi-conductor ceramic:

• Silicon Carbide is used in the production of resistant and hard materials such as bullet-proof vests.

•  It is used in the fabrication of jewelry.

• Formulation of abrasives.

• Construction of car clutches and car brakes.

• Used in photocatalytic processes as well as the production of field-emission transistors.

• Production of energy saving machines and equipment.

• Assemblage of solar powered systems and electric vehicles, due to its ability to support high electricity voltages.

• It is favored as a good substitute to high carbon combustion materials in production processes, to safeguard the environment.

Conclusion:

Semi-conductor ceramics are distinguished by their ability to withstand high temperature, their hardness and their ability to conduct electricity well. These traits also include their ability to resist corrosion, wear and tear, ionic bonding characteristics, color and shape. These distinguishing features also determine the suitability of their application.