This document discusses various electrical and magnetic materials. It covers semiconductors and their properties including single crystals, N-type and P-type semiconductors. It also discusses soft and hard magnets, superconductors, MEMS materials, nanomaterials, smart materials, shape memory alloys, piezoelectric materials and piezoceramic materials.

1. 4. ELECTRICAL AND
MAGNETIC MATERIALS

2. CH 4 ELECTRICAL AND MAGNETIC MATERIALS
• Semiconductors materials
• single crystals
• soft and hard magnets
• superconductors
• MEMS materials
• nano materials
• smart materials
• shape memory alloys
• Piezoelectric Materials
• piezoceramic materials
• Magnetostrictive Materials
• Metglasmaterials

3. • The goal of electronic materials is to generate and control
the flow of an electrical current
• Electronic materials include:
1. Conductors: have low resistance which allows electrical
current flow
2. Insulators: have high resistance which suppresses
electrical current flow
3. Semiconductors: can allow or suppress electrical
current flow
Semiconductors materials

4. • Good conductors have low resistance so electrons flow
through them with ease
• Best element conductors include:
– Copper, silver, gold, aluminum, & nickel
• Alloys are also good conductors:
– Brass & steel
• Good conductors can also be liquid:
– Salt water
Semiconductors materials

5. • The atomic structure of good
conductors usually includes
only one electron in their
outer shell.
– It is called a valence
electron.
– It is easily striped from the
atom, producing current
flow.
Copper Atom
Conductor Atomic Structure

6. Insulators
• Insulators have a high resistance so current does not flow
in them.
• Good insulators include:
– Glass, ceramic, plastics, & wood
• Most insulators are compounds of several elements.
• The atoms are tightly bound to one another so electrons
are difficult to strip away for current flow.

7. • Semiconductors are materials that essentially can be
conditioned to act as good conductors, or good insulators,
or any thing in between
• Common elements such as carbon, silicon, and
germanium are semiconductors
• Silicon is the best and most widely used semiconductor.
Semiconductors

8. Semiconductor Materials
(a) II III IV V VI
B C
Al Si P S
Zn Ga Ge As Se
Cd In Sb Te
(b) Elemental IV
compounds
Binary III-V
compounds
Binary II-VI
compounds
Si, Ge SiC, SiGe AlP, AlAs,
AlSb, GaP,
GaAs, GaSb,
InP, InAs,
InSb
ZnS, ZnSe,
ZnTe, CdS,
CdSe, CdTe

10. Semiconductor Valence Orbit
• The main characteristic of a semiconductor element is that
it has four electrons in its outer or valence orbit.

11. Crystal Lattice Structure
• The unique capability of
semiconductor atoms is
their ability to link together
to form a physical structure
called a crystal lattice.
• The atoms link together
with one another sharing
their outer electrons.
• These links are called
covalent bonds.
2D Crystal Lattice Structure

13. Types of Semiconductor
Materials
• The silicon doped with extra electrons is
called an “N type” semiconductor.
– “N” is for negative, which is the charge of an
electron.
• Silicon doped with material missing
electrons that produce locations called
holes is called “P type” semiconductor.
– “P” is for positive, which is the charge of a
hole.

14. Current Flow in N-type Semiconductors
• The DC voltage source has
a positive terminal that
attracts the free electrons in
the semiconductor and pulls
them away from their atoms
leaving the atoms charged
positively.
• Electrons from the negative
terminal of the supply enter
the semiconductor material
and are attracted by the
positive charge of the atoms
missing one of their
electrons.
• Current (electrons) flows
from the positive terminal to
the negative terminal.

15. Current Flow in P-type Semiconductors
• Electrons from the
negative supply terminal
are attracted to the
positive holes and fill them.
• The positive terminal of the
supply pulls the electrons
from the holes leaving the
holes to attract more
electrons.
• Current (electrons) flows
from the negative terminal
to the positive terminal.
• Inside the semiconductor
current flow is actually by
the movement of the holes
from positive to negative.

16. single crystals
• Certain minerals, such as quartz and the gemstones, often
occur as single crystals; synthetic single crystals, especially
silicon and gallium arsenide, are used in solid-state
electronic devices such as integrated circuits and light-
emitting diodes (LEDs)

17. Single crystal
turbine blades

20. Soft and hard magnets
• It was established that a small coil carrying a current behaved like
a bar magnet, i.e. as a magnetic dipole with magnetic moment μ
and this led Ampere to suggest that the origin of the magnetic
effect in materials lies in small circulating currents associated
with each atom
• These so-called amperian currents
each possess a magnetic moment
(μ =IA), and the total moment of
the material is the vector sum of all
individual moments
• The amperian currents are now identified with the motion of
electrons in the atom.

21. • Soft magnets are easily magnetized and demagnetized, exhibit
high values of saturation magnetization, low coercivity, and high
permeability.
• On the other hand, hard magnetic materials also exhibit high
saturation magnetization but are characterized by high coercivity,
being difficult to magnetize and demagnetize.
• Coercivity in a magnetic material is a measure of whether it is
able to resist an outside magnetic field without losing magnetism.

25. superconductors
• A superconductor is any
material that conducts
electricity without offering any
resistance to the flow of the
electric current.

27. • superconductors have zero resistance to current flow
below Tc

28. MEMS materials
• In the most general form,
MEMS consist of mechanical
microstructures, microsensors,
microactuators and
microelectronics, all
integrated onto the same
silicon chip.
• MEMS is a process technology
used to create tiny integrated
devices or systems that
combine mechanical and
electrical components.

30. The first commercial accelerometer from Analog
Devices (1990); its size is less than 1 cm2 (left), and
(b) capacitive sense plates, 60 microns deep (right)
• Automotive airbag sensors were one of the first commercial
devices using MEMS.
• They are in widespread use today in the form of a single
chip containing a smart sensor, or accelerometer, which
measures the rapid deceleration of a vehicle on hitting an
object.
• The deceleration is sensed by a change in voltage
• An electronic control unit
subsequently sends a
signal to trigger and
explosively fill the airbag.

34. Nanomaterials
• Nano-sized particles exist in nature and can be created from a
variety of products, such as carbon or minerals like silver, but
nanomaterials by definition must have at least one dimension
that is less than approximately 100 nanometers
• Nanotechnology is the science and applications of nano-
materials, and is growing at an ever increasing pace
• Nanomaterials can be categorized into four types such as:
o inorganic-based nanomaterials;
o carbon-based nanomaterials;
o organic-based nanomaterials; and
o composite-based nanomaterials.

36. smart materials

39. shape memory alloys

45. Piezoelectric Materials

48. Piezoceramic materials