Physics Final Essay
The understanding of physics and science has unlocked our current living standard and
economic development. America has invested in scientific research and development and we are
continually reaping the benefits. Technology is the practical application of scientific knowledge.
Quantum mechanics allows the technology in our cellphones work. Laws of electricity and
mechanics are all around us in the technology we use each day. One of the great advances in
technology came from the discovery and advancement piezoelectricity. Piezoelectric devices and
sensors are all around used daily.
What is it? The roots of the word come for press or squeeze, peizein,
and electricity. From the oxford dictionary, piezoelectricity is electric
polarization in a substance (esp. certain crystals) resulting from the application
of mechanical stress. Piezoelectric substances are able to convert mechanical
signals (such as sound waves) into electrical signals, and vice versa. These
properties occur naturally in minerals such as Berlinite, Sucrose, Quarts,
Topaz, and the Tourmaline group of minerals.
Pressure or force exerted on these substances polarizes the
structure inside the crystal and exerts and electric charge.
Normally the electric charge inside is in balance. This has to do
with the crystallographic structure. If you squeeze the crystals
you force the electric charge out of balance and get a positive
charge at one end and a negative charge at the other. It is kind
of like a battery. Now the effects of the charges (their dipole
moments) no longer cancel one another out and net positive
and negative charges appear on opposite crystal faces. By squeezing the crystal, you've produced
a voltage across its opposite faces. An electrical current passing through it also mechanically
deforms these crystals.
The discovery of these natural resources and their properties has had a significant impact
on our modern world. The Dutch East India Company originally brought the crystals to Europe
as gemstones. Large tourmaline crystals have a beautiful trigonal structure and vary in color
from dull brown and rather rock like to bright greens, reds, and purple.
These days these highly useful minerals are being mined for their application properties
from San Diego and Brazil to very productive
mines across the African continent. They are often
found when mining for other economic minerals
like copper or other gemstones.
Piezoelectricity was discovered and
developed in 1880 by Jacques and Pierre Curie
when studying how pressure generates electrical
charge in crystals such as quartz and tourmaline.
Pierre Curie was a French physicist, a pioneer in
crystallography, magnetism, piezoelectricity and
radioactivity. Clearly, he was a very busy man. In
1880, Pierre and his older brother Jacques demonstrated that an electric potential was generated
when crystals were compressed, the first demonstration of naturally occurring piezoelectricity.
Their initial experiments were rather innovative considering that they were performed with
nothing more than tinfoil, glue, wire, magnets and a jeweler's saw.
Shortly afterwards, to aid their work, they invented the Piezoelectric Quartz Electrometer.
In 1881, they demonstrated the reverse effect of piezoelectricity. Crystals could be made to
deform when subject to an electric field. These specific naturally occurring crystals and their
properties have been synthesized and refined in laboratories around the world. Almost all digital
electronic circuits now rely on this in the form of crystal oscillators.
Between 1882 and 1917 the core of the piezoelectric science was established, and
applications were being developed. At this time, identification of piezoelectric crystals on the
basis of asymmetric crystal structure was categorized. The reversible exchange of electrical and
mechanical energy was being harnessed. The laws of thermodynamics were used in quantifying
and calculating these complex relationships between mechanical, thermal and electrical forces
proved to be very productive.
In the following 25 years much more work was done to make this core knowledge grow
into a versatile and complete framework of piezoelectric laws, theory’s, and categories which
defined the 20 natural crystal classes in which piezoelectric effects occur. Mathematicians and
physicists defined all 18 possible macroscopic piezoelectric coefficients after a rigorous
thermodynamic treatment of crystal solids using tensorial analysis.
During the 25 years of research and analysis the world did not hold its breath for
piezoelectricity. A science of such subtlety as to require tensorial analysis just to define relevant
measurable effects was up against another burgeoning science, electro-magnetism. That field at
the time was maturing from a science to a technology, producing highly visible and amazing
machines.
Piezoelectricity was obscure even among crystallographers; the mathematics required to
understand it was complicated, and no publicly visible applications had been found for any of the
piezoelectric crystals.
War is an economic driver as well as a driver of science and research. In war
governments bring out the big buck to get the upper hand on their rival. This is how
piezoelectricity got its big break. Submarines were all the rage in World War I. But the
technology was crude and submarine warfare was supremely dangerous. Developments in
navigation systems implemented piezoelectric sensors in the form of sonar. These sensitive
receptors could turn vibrations under the water into
electrical signals. The piezoelectric crystal bends in
different ways at different frequencies. This bending is
called the vibration mode. The crystal can be made into
various shapes to achieve different vibration modes to
“see” under water.
Its use and success in submarine sonar in World
War I generated intense development interest in
piezoelectric devices. The success stimulated intense
development activity on all kinds of piezoelectric devices.
Megacycle quartz resonators were developed as frequency stabilizers for vacuum-tube
oscillators, resulting in a ten-fold increase in stability. New classes of material testing methods
were developed based on the propagation of ultrasonic waves and how these crystals responded
to them. Elastic and viscous properties of liquids and gases could be determined with
comparative ease for the first time. Another advance in technology in this time was that
previously invisible flaws in metal structural members could be detected.
New ranges of transient pressure measurement were opened up permitting the study of
explosives and internal combustion engines, along with a host of other previously immeasurable
vibrations, accelerations, and impacts. During their testing phase piezoelectric sensors were used
to measure the force of exploding atomic bombs.
Following World War I, most of the classic piezoelectric applications with which we are
now familiar were conceived and reduced to practice. In this time frame we developed
microphones, accelerometers, ultrasonic transducers, bender element actuators, phonograph pickups, and signal filters. However, the materials available at the time often limited performance
commercial opportunities.
During World War II, in the U.S., Japan and the Soviet Union, each developed research
groups to work on improving capacitor materials and discovered that certain
ceramic materials exhibited dielectric constants up to 100 times higher than
common cut naturally occurring crystals. Another class of materials called
ferroelectrics were made in labs that exhibit similar improvements in
piezoelectric properties. The discovery of easily manufactured piezoelectric
ceramics that were highly sensitive and offered great performance naturally
touched off another revival of intense research and development into
piezoelectric devices.
The advances in materials science that were made during this time
include the development of piezoceramics in the barium tatanate family and lead zirconate
family. Another is the advance of understanding of the perovskite crystal structure and its
correspondence to electro-mechanical activity. Later the development of chemical doping of
these structures with different metals in order to achieve desired properties for specific functions
was implemented. Through this method the properties became more predictable with things like
dielectric constants, stiffness and piezoelectric response making them much more practical and
easier to work with.
All of these advances contributed to establishing an entirely new method of piezoelectric
device development and gave scientists and businesses the option of tailoring a material to a
specific application. Historically speaking, it had always been the other way around.
This "lock-step" material and device development marched on all
over the world. This new technology was dominated by industry in
the U.S. We secured an early lead in development with strong
patents.
The number of applications worked on was massive. New
powerful sonar was developed. Based on new transducers in
geometric configurations such as spheres and cylinders. They could
be made much larger due to advances in ceramic casting. Electrical
circuits suddenly got better, and cheaper, with the ceramic
phonocartridge.
For those interested in science for science sake the Sonobouy was created and placed on
the ocean as a sensitive hydrophone to monitor the goings on of life under water, as well as
tracking ocean going vessels. Combustion engines also got a boost with piezoignition systems.
When the gas and air inside a cylinder is compressed these piezoelectric elements emit a spark,
igniting the mixture just like a spark plug.
For sound engineers, performers, and music lovers, ceramic audio tone transducer small, low power, low voltage, audio-tone transducer consisting of a disc of ceramic laminated to
a disc of sheet metal, improved the quality of recordings and playback. On stage microphones
improved in quality, and sensitivity and began to shrink smaller and smaller in size.
This great development in science, engineering and physics affects us to this day. Today
they are widely used in microphones, phonograph pickups, and earphones, and also to generate a
spark for igniting gas barbeques. These little sensors are everywhere. They are in your home
furnace as pressure sensors that tell the main board if it is working correctly. They are littered
about under the hood of your car for similar reasons. Countless pieces of equipment for our
military rely on them to keep them and us safe. The discovery of these once curious natural
properties has been a important widespread, yet unnoticed, advance for technology and our
society.