Biomedical Engineering Reference
In-Depth Information
2500
x=0.01
x=0.05
x=0.10
2000
1500
1000
500
0
0
50
100
150
200
250
300
350
400
Temperature(°C)
Figure 13.20
Dielectric constant versus temperature curves for Bi
1-x
Dy
x
FeO
3
(x=0.01,
0.05 & 0.1) at 10 kHz.
values of V, the current is proportional to V and can be described by Ohm's
law: I = V/R, where R is the electrical resistance. h e resistance R depends
on the intrinsic resistivity ρ of the material and on the dimensions of the
sample (length l and area A through which the current passes):
R = ρl/A
or
ρ =RA/l
(13.7)
In most materials (e.g., metals), the current is carried by electrons (elec-
tronic conduction), whereas in ionic crystals, the charge carriers are ions
(ionic conduction). h e electrical conductivity (the ability of a substance
to conduct an electric current) is the inverse of the resistivity ρ, therefore:
σ
= 1/
ρ
(13.8)
Since the electric i eld intensity in the material is E = V/L.
13.4.2.2 Measurement
h e dc electrical conductivity measurements were carried out in the tem-
perature range from 300 K to 800 K in air atmosphere using the laboratory
made two-probe method setup. h e dc current was measured by digital
picoammeter model DPM-100. h e dc power supply of range 0-8 volts
was used to supply i xed dc voltage across the sample.
