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Dielectric Materials Used in Communication

Materials used for insulators and dielectrics in communication apparatus are many and varied. A few of the common materials are listed in Table IV.

The power factors in Table IV indicate the dielectric losses in the materials. For paper dielectrics the dielectric constants range from about 3 to 5, and the power factors vary from about 0.1 to 0.5 per cent, depending on the nature of the paper-impregnating substance. Ceramic dielectrics such as titanium dioxide are used in radio circuits where constancy of capacitance with temperature change is desired and where the capacitors must be physically small.

TABLE IV

ELECTRICAL CHARACTERISTICS OF MATERIALS USED FOR INSULATORS

AND DIELECTRICS (From references 3 and 13.)

Dielectric Power Factor - Per Cent Machine-Material Constant 60 cycles 1000 cycles 106 cycles ability

Cellulose acetate

6-8

7

. .

3-6

Very good

Cellulose nitrate

4-7

5-9

5

5

Very good

Fiber

4-5

6-9

5

5

Very good

Glass, Pyrex

4.5

0.5

0.2

Very poor

Mica, clear India

7-7.3

0.03

0.02

0.02

Bakelite, "low loss"

5.3

2.5

1.4

0.7

Poor

Porcelain, "wet process"

6.2-7.5

2

1

0.7

Very poor

Rubber, hard

2-3

1

1

0.5-0.9

Fair

Steatite

6.1

1

0.4

0.3

Very poor

Styrene (polymerized)

2.4-2.9

0.02

0.02

0.03

Good

Titanium dioxide

90-170

0.1

0.06


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Last Update: 2011-05-04