Question

Which material among the following possesses excellent dielectric properties and good reliability for use in making capacitors?
1. Silicon monoxide
2. Silicon dioxide
3. Tin oxide
4. Chromium oxide

Answer 1

Correct Answer - Option 2 : Silicon dioxide

Concept:

The SI unit of the dielectric strength is volts per meter (V/m)

It is also common to see related units as volts per cm(V/cm), megavolts per meter(MV/m)

Dielectric strength is defined as for a pure electrically insulating material, the maximum electric field that the material can withstand under ideal conditions without undergoing electrical breakdown and becoming electrically conductive (i.e. without failure of its insulating properties).

The different materials and their dielectric strength are shown below:

Substance	Dielectric strength (MV/m)
Helium	0.15
Air	3
Sulfur hexafluoride	8.5 - 9.8
Alumina	13.4
Window glass	9.8 - 13.8
Borosilicate glass	20 - 40
Silicon oil, mineral oil	10 - 15
Benzene	163
Polystyrene	19.7
Neoprene rubber	15.7 - 26.7
Distilled water	65 - 70
Fused silica	470 - 670
Waxed paper	40 - 60
Mica	118
Diamond	2000

 

The most common dielectric materials include aluminum & tantalum oxide, ceramic, plastic film, polymer, glass, mica, and paper.

• For high-frequency applications, ceramic capacitors are a good option. However, these capacitors have a poor aging performance.
• Mica and glass capacitors are suitable for applications that demand extremely high stability, reliability, and tolerance to high voltages and temperatures. However, these capacitors are typically expensive and are, therefore, not commonly used in low-cost devices.
• Aluminum or tantalum plate capacitors with an oxide dielectric material are widely used for applications that require high capacitance.

Silicon-based dielectrics such as silicon dioxide and silicon nitride are commonly used in high-density capacitors.

Capacitors with silicon dielectrics are ideal for applications that demand high stability, reliability, and tolerance to high temperatures.

The performance characteristics of these capacitors make them a suitable choice for use in harsh environment applications.

Strengths of silicon-based dielectrics

1. High stability at high temperature
2. High potential for miniaturization
3. Leakage current stability at high temperature
4. Low failure rate

Limitations

• Limited maximum capacitance
• Charge leakage

Conclusion:

Option 2 is correct.