Middleton W.M. (ed.) Reference Data for Engineers: Radio, Electronics, Computer and Communications
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TABLE
2.
PHYSICAL
PROPERTIES
Density
at
20
“C
Wm3)
2.70
13.67
6.62
1.78*
5.73
3.5
1.82
9.80
2.46
3.12
8.65
1.54
Relative
Hardness
Melting
Point (“C)
Boiling
Point (“C)
Atomic
Symbol Number
Ac
89
A1
13
Am
95
Sb
51
ArorA
18
Actinium
Aluminum
Americium
Antimony
Argon
Arsenic (gray)
Astatine
Barium
Berkelium
Beryllium
Bismuth
Boron
Bromine
Cadmium
Calcium
Californium
Carbon
Cerium
Cesium
Chlorine
Chromium
Cobalt
Copper
Curium
Dysprosium
Einsteinium
Erbium
Europium
Fermium
Fluorine
2.9
3
1
050
660
994
630.5
-189.2
820t.
302
725
1278
271.3
-7.2
320.9
842
2 300
3 200
2 467
2
600
1750
-185.7
615**
337
1
640
2 970
1560
2
550**
58.8
165
1 487
As
33
At
85
Ba
56
Bk
97
Be
4
Bi
83
B
5
Br
35
Cd
48
Ca
20
Cf
98
C
6
Ce
58
cs
55
c1
17
Cr
24
co
27
cu
29
Cm
96
DY
66
Es
or
E
99
Er
68
Eu
63
Fm
100
F
9
3.5
3
2.5
9.5
2.0
2.22
6.9
1.87
3.21*
lot
2.5
0.2
>3
500
795
28.5
-100.98
4 827
3 468
690
-34.7
2 612
2 900
2 595
2 600
7.14
8.9
8.96
13.51
8.54
9
5
3
1 890
1 495
1083
1 340
1
407
9.05
5.26
1
497
826
-220
27
1312
29.78
937.4
1
063
2 220
<-272§
1461
156
113.5
-259.14
2 410
1535
-156.6
920
2 900
1439
-188
1.69*ti
Francium
Gadolinium
Gallium
Germanium
Gold
Fr
87
Gd
64
Ga
31
Ge
32
Au
79
Hf
72
He
2
Ha
67
H
1
In
49
I
53
Ir
77
Fe
26
Kr
36
La
57
Lw
103
Pb
82
Li
3
Lu
71
Mg
12
Mn
25
Md or Mv
101
Hg
80
677
3 000
2 403
2 830
2 966
7.89
5.91
5.36
19.3
13.31
0.1664*
8.803
0.08375*
7.31
4.93
22.4
7.87
3.448*
6.15
1.5
6.2
2.5
Hafnium
Helium
Holmium
Hydrogen
Indium
Iodine
Iridium
Iron
Lanthanum
Lawrencium
Lead
Lithium
Lutetium
Magnesium
Manganese
Mendelevium
Mercury
Krypton
4 602
-268.94
2 600
-252.8
2
050
1.2
184.3
4 527
3 000
-152.3
3 469
6.15
4
11.34
0.53
9.84
1.74
7.44
13.55
1.5
0.6
2
5
.O
1.5
327.4
179
1652
65
1
1 244
1 744
1336
3 327
1100
2 097
-38.87
356.9
4-9
OF
THE
ELEMENTS
Latent Heat Specific Heat
Thermal
Linear Elasticity
Tensile
of Fusion at
20
"C
Conductivity at Expansion at
Modulus Strength
(4.184
J/g)
(4.184
J/g"C)
20
"C (W/cm"C)
20
"C
(1O4/T)
(GN/m*)
(MN/m2)
93 0.226
2.18 22.9 71.1 61.8
38.3 0.049
0.19 8.5-10.8 77.5 10.3
6.7 0.125 1.7
x lo4
0.082 4.7
324
12.5
16.2
13.2
3.8
23
75.6
58.4
50.6
10.1
0.425 1.64 12
0.0294 0.084 13.3
0.307 2
0.107
0.055 0.91 29.8
0.145 25
0.165 0.24 0.64.3
0.042
0.052 97
0.226 0.072
x
lo4
0.11 0.69 6.2
0.1001 0.69 12.3
0.0921 3.94 16.5
19.2 0.079
18
16.1 0.031 2.96 14.2
0.073
294
31.4
53.9
20.6
4.9
206
108
71.6
117
70.6
55.9
88.8
237
221
113
1.25 13.9
x
1v
15 3.415 17
x
lo4
0.057 0.24 33 2.9
15.8 0.052
43.5
x
104 93
33 0.032 1.4
6.5 515
65
0.108
0.79
11.7 196
201
0.89
x
IO4
0.045
6.3 0.030 0.35 28.7
159 0.79 0.71 56
17.7 13
88 0.249 1.55 25.2 45.1 89.7
64.8 0.107
23 157 283
2.7 0.033 0.084
Continued
on
next page
4-1
0
TABLE
2
(CONT). PHYSICAL
Density
Atomic at
20
"C
Relative Melting Boiling
Symbol Number (g/cm3) Hardness Point
("C)
Point
("C)
Molybdenum
Neodymium
Neon
Neptunium
Nickel
Niobium
Nitrogen
Nobelium
Osmium
Oxygen
Palladium
Phosphorus
Platinum
Plutonium
Polonium
Potassium
Praseodymium
Promethium
Protactinium
Radium
Radon
Rhenium
Rhodium
Rubidium
Ruthenium
Samarium
Scandium
Selenium
Silicon
Silver
Sodium
Strontium
Sulfur
Tantalum
Technetium
Tellurium
Terbium
Thallium
Thorium
Thulium
Tin
Titanium
Tungsten
Uranium
Vanadium
Xenon
Yitterbium
Yttrium
Zinc
Zirconium
Mo
42
Nd
60
Ne
10
Np
93
Ni
28
Nb
41
N
7
No
102
os
76
0
8
Pd
46
P
15
Pt
78
Pu
94
Po
84
K
19
Pr
59
Pm
61
Pa
91
Ra
88
Rn
86
Re
75
Rh
45
Rb
37
Ru
44
Sm
62
sc
21
Se
34
Si
14
Ag
47
Na
11
Sr
38
S
16
Ta
73
Tc
43
Te
52
Tb
65
T1
81
Th
90
Tm
69
Sn
50
Ti
22
w
74
U
92
V
23
Xe
54
Yb
70
Y
39
Zn
30
Zr
40
10.2
7.05
0.8387%
20.45
8.9
8.57
1.1649*
22.48
1.3318*
12
1.82
21.45
19.82
9.2
0.86
6.63
15.37
5
4.40%
20
12.44
1.53
12.2
7.7
2.5
4.81
2.4
10.49
0.97
2.6
2.07
16.6
11.49
6.24
8.27
11.85
11.5
9.33
7.3
4.54
19.3
18.7
5.68
5.495%
6.98
5.51
7.14
6.4
6
5
7.0
4.8
4.3
0.5
6
0.3
6.5
2
7
2.7
0.4
1.8
2.0
7
2.3
1.2
1.8
4
7
2.5
4.7
2 610
1
024
-248.7
640
1453
2 468
-209.9
3 000
-218.4
1552
44.1
1769
639.5
254
935
1
027
1
227
700
-7
1
3 180
1
966
63.65
38.5
2 250
1072
1539
217
1410
960.8
97
769
116
2 996
2 200
1356
449.5
303.5
1
800
1
545
1675
3 410
1133
1890
-111
824
1
495
231.89
419.4
1852
4 800
3 027
-245.9
3 902
2 732
5
127
-195.8
5
000
-183
2 927
280
3 827
3 235
962
774
3 127
2 027
4 027
1525
5
627
3 727
688
3 900
1 900
2 727
685
2 355
2 212
892
1384
444.6
-61.8
5 425
4 700
990
2 800
1457
4 200
1
727
2 270
3 260
5
660
3 818
3 400
-107
1
421
2 927
907
4 317
*gL.
+diamond.
i36
atm.
526
atm. **sublimes. t+At
15
"C.
4-1
1
hOPERTIES
OF
THE
ELEMENTS
Latent Heat Specific Heat
Thermal
Linear
Elasticity Tensile
of
Fusion
at
20
"C
Conductivity at
Expansion at
Modulus
Strength
(4.184
J/g)
(4.184
J/g"C)
20
"C (W/cm°C)
20
"C (104/oC)
(GN/m2)
(MN/m2)
69.0 0.065
0.045
1.46
4.57
x
1cv
4.9 343
1177
317
73.8
68.0
6.2
0.112
0.064
0.247
0.9
0.52
13.3 206
7.1
34.0
3.3
34.2
5.0
27.1
0.031
0.218
0.059
0.177
0.032
0.61
0.70
0.69
0.08
0.99
5
117
147
137
157
11.8
8.9
125
3.0
0.032 54
14.5 0.177
0.458
83
0.035
50.0 0.060
6.1 0.080
0.061
1.5 8.1
90
9.1
29.4
16.0 0.077
0.005
37
430.0 0.176 0.84 2.8-7.3
24.3 0.056 4.08 18.9
27.5 0.295 1.35 71
25
9.3 0.175 26.4
x
104 6.4
41.0 0.036 0.54 6.6
25.3 0.047 0.060 16.8
108
70.6
148
186
20.6
490
11.0
7.2 0.031 0.39 28
549
13.7
2 650
17.0 0.028 0.41 11.1
14.4
100.0
44.0
0.054
0.142
0.034
0.64
0.2
1.99
23
8.5
4.3
403
343
83.4
12.0 0.028 0.25 13.4
98.0 0.115 0.60
8
5.9
x
lV
24.1 0.09
1.1 17.39 82.4 103
0.066
5.6 73.5 294
4-1
2
REFERENCE
DATA
FOR ENGINEERS
+
,@~~~~~~~'~
*
ACTINIDES
+3
+3
+3
+3
+3
+2
+2 +3
c3
+3
13
+3
+3
+2
+3
La
+4Ce
Pr Nd Pm
+3Srn+3Eu
Gd
Tb
Dy
Ho Er
Tm
+3Yb
Lu
57 58 59 60 61 62 63 64 65 66 67 68 69 70
71
AC
Th
+5Pa:2
U :2Np:;Pu$Arn
Crn
+4Bk
Cf
Es
fm
Md No
Lw
89 90 91 +692 +693 +694 +6 95 96 97 98 99
loo
101 102 103
+3
+4
+4
+3
+3
+3
+3
+3
+3 +3
Fig.
1.
Periodic classification
of
the elements.
INSULATING MATERIALS
where,
The permittivity,
E,
of
an
insulating material is
€0
=
permittivity
of
free space,
P
=
flux
density from dipoles within the
dielectric medium,
E
=
electric-field intensity,
P/E
=
electric susceptibility.
defined
by
€
=
€0
+
(P/E)
1000 1400
DEG.C
DEGREES CELSIUS
Fig.
2.
Temperature-emf characteristics of thermocouples.
4-1
3
CHART
1.
GALVANIC
SERIES
IN
SEA WATER
Corroded end (anodic) Lead
Magnesium
Magnesium alloys Muntz metal
Zinc
Naval brass
Galvanized steel
Galvanized wrought
iron
Nickel (active)
Inconel (active)
Aluminum:
Tin
Manganese bronze
52SH, 4S, 3S, 2S, 53ST
Aluminum clad Yellow brass
Admiralty brass
Aluminum bronze
Copper
A17ST, 17ST,
24ST
Ambrac
Cadmium Red brass
Aluminum: Silicon bronze
70-30 copper-nickel
Mild steel Comp.
G,
bronze
Wrought iron Comp.
M,
bronze
Cast
iron
Ni-resist Nickel (passive)
Inconel (passive)
13% chromium stainless steel (type 410-active) Monel
50-50 lead-tin solder
18-8 stainless steel type 304 (active)
18-8-3 stainless steel type 316 (active)
18-8 stainless steel type 304 (passive)
18-8-3 stainless steel type 316 (passive)
Protected end (cathodic or most noble)
It is often convenient to use the relative permittivity,
E,,
defined by
er
=
€/EO
The relative permittivity,
E,.,
is a function of temper-
ature and frequency. From Table
9,
which gives the
values of
E,.
as a function of frequencies at room tem-
perature,
it
is easy to get values
of
E
from
E
=
€,./Eo
In
the international system
of
units, the permittivity
of vacuum
is
equal to
E,,
=
8.854
x
F/m
and we have
Coulomb’s Law
F
=
(1/4w~n~~-)(qlqdR~)
Gauss’s Law
aJ
=
(Eg€,.)-l2qj
The dissipation factor of an insulating material
(Table
9)
is defined as the ratio of the energy dissipated
to the energy stored
in
the dielectric per hertz, or as the
tangent
of
the loss angle. For dissipation factors less
than
0.1,
the dissipation factor may be considered
equal to the power factor of the dielectric, which is the
cosine of the phase angle by which the current leads
the voltage.
Many of the materials listed
are
characterized by a
peak dissipation factor that occurs somewhere in the
frequency range, this peak being accompanied by a
rapid change in the permittivity. These effects are the
result of a resonance phenomenon occurring in polar
materials. The position
of
the dissipation-factor peak in
the frequency spectrum is very sensitive to temperature.
An increase in the temperature increases the frequency
at which the peak occurs,
as
illustrated qualitatively in
Fig.
3.
Nonpolar materials have very low losses without
a noticeable peak;
the
permittivity remains essentially
unchanged over the frequency range.
Another effect that contributes to dielechic losses is
that of ionic
or
electronic conduction.
This
loss,
if
present, is important usually at the lower end of the fre-
quency range only and is distinguished by the fact that
the dissipation factor varies inversely with frequency.
TABLE
3.
THERMOCOUPLES
AND
THEIR
CHARACTERISTICS
e
d
P
Platinum/Platmum Platiuum/Platinum Carbon/Silicon
Copper/Constantan Iron/Constantan Chromel/Constantan Cbromel/Alumel Rhodium
(1
0)
Rhodium
(13)
Carbidc
Composition, percent
100
Cul60 Cu
40
Ni
100
Fe/60 Cu
40
Ni
90
Ni
10
Cr/
90
Ni
10
Cr/
P1/90
Pt
10
Rh
Pt/X7
Pt
13
Rh C/SiC
55
Cu
45
Ni
94
Ni 2A13
Mn
1
Si
*Range
of
application, "C
-200
to
+
300 -200
to
+
1100
0
to
+
1100 -200
to
+
1200
0
to
+
1450
0
to
+
1450
0
to
+
2000
Resistivity, p&an
1.75 49 10 49 70
49
70
29.4 10 21
Temperature cocfficicnt
of
0.0039 0.00001 0,005 0,00001 0.00035 0.0002 0.00035 0.000125 0.0030 0.0018
resistivity, per "C
Melting temperature, "C
emfin millivolts; refer-
ence junction at 0°C
Influence
of
temperature
and gas atmosphere
Particular applications
1085 1190
100°C
4.24mV
200 9.06
300 14.42
Subject to oxidation
and alteration above
400
"C due
to
Cu,
above
600"
due
to
con-
stantan
wire. Ni-plat-
ing
of
Cu tube gives
protection
in
acid-con-
taining gas. Contamina-
tion
of
Cu
affects
calibration greatly.
Resistance to oxide.
atm. good. Resistance
to
reducing atm. good.
Requires protection
from acid fumes.
Low temperature,
industrial. Intemal-
combustion engine.
Used as a tube elemcnt
for measurements in
steam linc.
1535 1190
100°C
5.28mV
200 10.78
400 21.82
600 33.16
800 45.48
1000 58.16
Oxidizing and reducing
atmosphere have little
used in dry atmosphere.
Resistance to oxidation
good
to
400
"C. Resis-
tance to reducing atmo-
sphere good. Protect
from oxygcn, moisturc,
sulphur.
effect
on
accuracy. Best
Low temperature, indus-
trial. Steel annealing,
boilcr flues, tube stills.
Used in reducing or
ncu-
tral atmosphere.
1400 1190
100°C
6.3mV
200 13.3
400 28.5
600 44.3
Chrome1 attacked by
sulphurous atmosphere.
Resistance
to
oxidation
good. Resistance to
reducing atmosphere
poor.
1400 1430
100°C
4.1 mV
200 8.13
400 16.39
600 24.90
800 33.31
1000 41.31
1200 48.85
1400 55.81
Resistance to oxidizing
atmosphere very good.
Resistance
to
reducing
atmosphere
poor.
Affected by sulphur,
reducing or sulphurous
gas,
SO,
and
H,S.
Used in oxidizing atmo-
sphere. Industrial.
Ccramic kilns, tubc
stills, electric furnaces.
1755
1700
100
200
400
600
800
1000
1200
1400
1600
1°C
0.643mV
1.436
3.251
5.222
7.330
9.569
11.924
14.312
16.674
100
"C
200
400
800
1000
1200
1400
1600
6no
0.646mV
1.464
3.398
5.561
7.927
10.470
13.181
15.940
18.680
Resistancc to oxidizing atmosphcrc vcry good.
Resistance
to
reducing atmosphere poor. Susccpti-
ble to chemical alteration by As, Si,
1'
vapor in
reducing gas (C02,
H2,
HIS,
SO2).
Pt corrodes eas-
ily above
1000
"C. Used in gas-tight protecting
tube.
International Standard
630
to
1065
"C.
Similar to Pt/PtRh
(10)
but bas higher emf.
3000 2700
1210
"C
353.6 mV
1300 385.2
1360 403.2
1450 424.9
Used as tube element.
Carbon sheath chemi-
cally incrt.
Steel furnace and ladle
temperatures. Labora-
tory measurements.
JJ
rn
n
rn
JJ
rn
2
c)
rn
:
3
6
1
JJ
D
5
m
JJ
v)
*
For prolonged use; can be used at higher temperature
for
short periods.
TABLE
4.
THERMAL
ELECTROMOTIVE
FORCE
OF
PLATINUM-RHODIUM
ALLOYS
VERSUS PLATINUM*
Electromotive Force (mV)
Percent Rhodium
Temp.("C)
0.5 1.0 5.0 10.0 20.0 40.0 80.0 100.0
0
0.00
0.00
0.00
0.00
0.00
0.00 0.00
0.00
100 +0.10 +0.18 +0.54 +0.64 +0.63
+0.65 +0.62
+0.70
200 0.20 0.37 1.16 1.43 1.44 1.52 1.49 1.61
300 0.29 0.57 1.82 2.32 2.40
2.55 2.55
2.68
400 0.39
0.76 2.49 3.25
3.47 3.70 3.77 3.91
500 0.48 0.94 3.17 4.22
4.63 4.97
5.12 5.28
600 0.58 1.12 3.86 5.22 5.87
6.36 6.60
6.77
700 0.67 1.30 4.55
6.26 7.20
7.85 8.20 8.40
800 0.76 1.48 5.25 7.33 8.59
9.45
9.92 10.16
900 0.85 1.66 5.96
8.43 10.06 11.16 11.76 12.04
1000 0.94 1.84 6.68
9.57 11.58
12.98 13.73 14.05
1100 1.03 2.02 7.42 10.74 13.17 14.90 15.81 16.18
1200 1.13 2.20 8.16 11.93 14.84
16.91 17.99
18.42
*
From
Smithsonian
Physical
Tables,
9th revised ed., Vol.
120
(Washington, DC: Smithsonian
Institution,
1969).
TABLE
5.
RESISTIVITIES
OF
METALS
AND
ALLOYS
Material
Resistivity Temperature Temperature
Form
(x
104
fl.cm) ("C) Coefficient ("C-l)
Alumel
Aluminum
Antimony
Arsenic
Beryllium
Bismuth
Boron
Brass
(66
Cu
34
Zn)
Cadmium
Carbon
Cerium
Cesium
Chromax
(15
Cr,
35
Ni, balance Fe)
Chrome1
Chromium
Cobalt
Constantan
(55
Cu,
45
Ni)
Copper (commercial annealed)
Gallium
Gold
Hafnium
Indium
Iridium
solid
liquid
solid
liquid
solid
solid
liquid
solid
liquid
solid
diamond
graphite
liquid
solid
solid
liquid
solid
liquid
solid
liquid
solid
liquid
solid
33.3
20.3
2.62
123
39.2
35
128.9
115
1.8
x
10'2
3.9
34
7.5
5
x
1020
1400
78
36.6
20
18.83
100
70-110
4.57
2.6
9.7
44.2
21.3
27
53
30.8
1.7241
2.44
2.19
32.1
29
9
5.3
0
670
20
800
20
0
20
300
20
0
20
400
20
15
20
20
30
20
0
20
0
0
20
20
1083
20
30
0
1063
20
0
20
157
20
20
0.0012
0.0039
0.0036
0.0042
0.004
0.002
0.0038
-0.0005
0.00031
0.0001 1-0.000054
0.0033
+0.0002
0.0039
0.0034
0.00498
0.0039
Continued
on
next page
-1
6
REFERENCE
DATA
FOR ENGINEERS
TABLE
5
(COAT).
RESISTIVITIES
OF
METALS
AND
ALLOYS
Resistivity Temperature Temperature
Material
Form
(X
10"
R,cm)
("C)
Coefficient
("C-l)
Iron
KovarA
(29
Ni,
17
Co,
0.3
Mn, balance
Fe)
Lead
PbO,
Lithium
Magnesium
Manganese
MnOz
Manganin
(84
Cu,
12
Mn,
4
Ni)
Mercury
Molybdenum
Monel metal
(67
Ni,
30
Cu,
1.4 Fe,
1
Mn)
Neodymium
Nichrome
(65
Ni.
12
Cr,
23
Fe)
Nickel
Nickel-silver
(64
Cu,
18
Zn,
18
Ni)
Niobium
Osmium
Palladium
Phosphor bronze
(4
Sn,
0.5
P,
balance Cu)
Platinum
Plutonium
Potassium
Praseodymium
Rhenium
Rhodium
Rubidium
Ruthenium
Selenium
Silver
Sodium
Steel
(0.4-0.5
C, balance
Fe)
Steel, manganese
(13
Mn,
1
C,
86
Fe)
Steel, stainless
(0.1 C, 18
Cr,
8
Ni, balance
Fe)
Strontium
Sulfur
Tantalum
Thallium
Thorium
Tin
Titanium
Tophet
A
(80
Ni,
20
Cr)
Tungsten
wZ05
wo3
Uranium
Zinc
Zirconium
liquid
solid
liquid
solid
liquid
solid
solid
solid
solid
solid
solid
liquid
solid
solid
liquid
solid
liquid
solid
9.71
45-84
98
21.9
92
45
9.3
4.46
5
6
000
000
44
95.8
21.3
5.17
4.77
42
79
100
6.9
28
12.4
9
10.8
9.4
10.5
150
13
7
68
19.8
5.1
12.5
10
1.2
1.62
9.7
4.6
13-22
70
90
23
13.1
18.1
18
11.4
47.8
2
x
1023
108
5.48
450
2
x
10"
29
35.3
6
40
20
20
400
20
230
20
20
20
20
20
20
-50
0
20
20
18
20
20
20
20
20
20
20
20
20
62
20
25
20
20
20
20
20
20
100
20
20
20
20
20
20
20
20
20
20
25
20
20
20
20
0
420
20
20
0.0052-0.0062
0.004
0.003
0.005
0.004
f
0.0002
0.00089
0.0033
0.002
0.00017
0.0047
0.00026
0.0042
0.0033
0.003
0.003
0.006
0.0046
0.0038
0.003
0.001
0.003
0.004
0.0021
0.0042
0.00014
0.0045
0.0021
0.0037
0.0044
4-1
7
TABLE
6.
ELECTRICAL RESISTIVITY
OF
ROCKS
AND
SOILS*
Resistivity
(Cl.cm)
Igneous Rocks
Granite
107-1
09
Lava
flow
(basic)
106-1
07
Lava, fresh
3
x
105-106
Quartz vein, massive
>
106
Marble
4
x
108
Marble, white
10'0
Marble. yellow
10'0
Schist, mica
107
Shale, bed
105
Shale, Nonesuch
104
Limestone
104
Limestone, Cambrian
104-1
05
Sandstone
105
Sandstone, eastern
3
x
103-104
Clay, blue
2
x
104
Clay,
fire
2
x
105
Clayey earth
104-4
x
104
Gravel
105
Sand,
dry
105-106
Sand, moist
105-106
Metamorphic Rocks
Sedimentary
Rocks
Unconsolidated Materials
*
From
Smithsonian Physical Tables,
9th revised ed., Val.
120
(Washington, DC: Smithsonian Institution,
1969).
Increase
in
temperature increases the loss due to ionic
conduction because of increased ionic mobility.
The data given on dielectric strength are accompa-
nied by the thickness of the specimen tested because
the dielectric strength, expressed in volts/mil, varies
inversely with the square root of thickness, approxi-
mately.
The direct-current volume resistivity of many mate-
rials
is influenced by changes in temperature or humid-
ity. The values given in the table may be reduced
several decades by raising the temperature toward the
higher end of the working range of the material, or by
raising the relative humidity of the air surrounding the
material to above
90
percent.
MAGNETIC MATERIALS*
All materials that are magnetized by
a
magnetic
field
are
called magnetic materials. Depending on the
magnetic response,
various
kinds of magnetism
are
classified. Most magnetic materials of commercial
*
This section was contributed by the late Gilbert
Y.
Chin.
TABLE
7.
SUPERCONDUCTIVITY
OF
SOME METALS,
ALLOYS,
AND
COMPOUADS*
Material Critical Temperature
(K)
NbC
Niobium
TaC
Pb-As-Bi
Pb-Bi-Sb
Pb-Sn-Bi
Pb-As
MoC
Lead
Bi6T1,
Lanthanum
Tantalum
Vanadium
TaSi
Mercury
PbS
Tin
Indium
ZrB
wc
Rhenium
Mo~C
Thallium
w2c
Au2Bi
cus
TiN
Thorium
VN
Aluminum
Gallium
Tic
zinc
Uranium
Osmium
Zirconium
Cadmium
Titanium
Ruthenium
Hafnium
N2Pbj
10.1
9.22
9.2
9.0
8.9
8.5
8.4
7.7
7.2
7.2
6.5
5.5
5.2
4.4
4.3
4.2
4.15
4.1
3.8
3.71
3.38
2.82
2.8
2.57
2.4
2.4
2.05
1.84
1.6
1.4
1.32
1.3
1.15
1.12
1.1
0.95
0.75
0.71
0.54
0.54
0.53
0.47
0.35
*
hformation on recently discovered ceramic superconductors
is posted at
www.ceramics.nist.gov/srd
and at www.iastate.edu.
importance today are ferromagnets or ferrimagnets.
Iron, nickel, cobalt, and their alloys are examples of
ferromagnets; spinel ferrites and garnets are examples
of ferrimagnets. These exhibit spontaneous magnetism
and develop
a
flux density
B
upon application of
a
magnetic field of strength
H
in accordance with
B=F&+J
In
this equation,
po
=
1.257
x
H/m is the per-
meability of free space, and
J
is the magnetic polar-
ization. The units of
B
and
d
are
teslas (T) or webers