Exploring The Piezoelectric Property Of Quartz Mineral.

 Lately, I have been interested in the piezoelectric property of quartz minerals. It is used in various applications such as; microphones, pressure sensors, and electric generators. To know about the piezoelectric property of quartz minerals, we first have to understand the piezoelectric effect. The piezoelectric is the ability to convert mechanical stress into electrical charge. The piezoelectric effect occurs at the crystal level of the Quartz mineral.There are several types of crystals including pyroelectric, ferroelectric, and piezoelectric.

           

 These crystals are able to build up signals in the form of potential across the crystal. This can lead to current flow which results in vibration or movement over a range of frequencies depending on the material type. Another essential characteristic of these crystals is that they're able to convert the static charge into mechanical vibrations. This is called the inverse piezoelectric effect which converts mechanical vibrations into electrical potentials. Piezoelectricity was discovered by Jacques and Pierre Curie in 1880.  the word “piezoelectricity” comes from the Greek word “piezein” meaning “to squeeze” or “to press” and “electricity” which means “charged with electricity”.

How quartz watches and clocks work - Explain that Stuff


Quartz Mineral

Quartz is one of the most abundant minerals and is found in many different types of rocks. Quartz belongs to a group of minerals called silicates. Silicates have structures based on clusters of silicon and oxygen atoms called silica tetrahedra. Quartz belongs to the trigonal crystal system. The ideal crystal shape is a six-sided prism terminating with six-sided pyramids at each end.

 In nature quartz crystals are often twinned (with twin right-handed and left-handed quartz crystals), distorted, or so intergrown with adjacent crystals of quartz or other minerals as to only show part of this shape, or to lack obvious crystal faces altogether and appear massive. Well-formed crystals typically form in a 'bed' that has unconstrained growth into a void; usually, the crystals are attached at the other end to a matrix and only one termination pyramid is present.

Crystal Clear To White Quartz


Crystal Structure Of the Quartz Mineral

 The tetrahedra structure are linked together covalently with Quartz being one giant covalently bonded network solid.  Each bond is made up of two electrons shared between two atoms. The piezoelectric property of quartz is indicated by a change in shape when it receives an electrical charge. The change in shape is reversible; when the charge is removed, the quartz returns to its original shape. As a result, it can be used as a transducer: converting mechanical motion into electrical energy (and vice versa). This property has been put to use in thousands of devices including watches, microphones, pressure gauges, accelerometers.

Quartz Crystal Structure[ Oxygen-Silicon]


How Piezoelectric effect is created in Quartz minerals?

In a crystal of piezoelectric material, the positive and negative charges are separated by a fixed distance. When a mechanical force is applied to a piezoelectric material with no net charge that is when the number of positive charges equals the number of negative charges a dipole moment results. Piezoelectricity is a form of electric polarization produced in a crystal by the application of mechanical stress. Piezoelectricity is the charge that accumulates in certain solid materials such as crystals, some ceramics, and biological matter such as bone, DNA, and various proteins in response to applied mechanical stress.

 The piezoelectric effect is understood as the internal generation of electrical charge in response to an applied mechanical force. The inverse piezoelectric effect is the internal generation of a mechanical strain (deformation) resulting from an applied electrical field. This creates an internal voltage between opposite faces of the crystal that is proportional to the applied force. The most common example of this can be seen in a sound speaker: A speaker consists of a cone and coil arrangement suspended in a magnetic field. When a voltage is applied to the coil, it generates a magnetic field that pushes against the fixed magnetic field created by permanent magnets around it, causing it and therefore the attached cone to vibrate, creating sound. The piezoelectric effect is understood as the linear electromechanical interaction between the mechanical and the electrical state in crystalline materials with no inversion symmetry.

Piezoelectric effect

Industrial Application of  Quartz  Piezoelectric Effect

Quartz Wristwatch

A great example of the piezoelectric effect can be found in a quartz wristwatch. This watch generates an alternating current by means of a small piece of quartz crystal that is cut into a precise shape. The electrical current oscillates at a constant frequency (32,768 Hz) and is used to drive the motor that moves the hands on the watch face. The first practical application of piezoelectricity was by Paul Langevin in 1917 who used quartz crystals to make a sonar device for detecting submarines during World War I.

Quartz watch ubt EXP 123

 Phonograph Pickups

Early use of this property of quartz crystals was in phonograph pickups. One of the most common piezoelectric uses of quartz today is as a crystal oscillator. The quartz clock is a familiar device using the mineral. The resonant frequency of a quartz crystal depends on its shape, size, and crystal orientation relative to the applied electric field. This means that on top of the size-frequency relationship, there exists another factor that relates the vibration frequency to the electric field.

Turntable Plate Vinyl Record

Electronics

Piezoelectric devices have many uses in the electronics industry including, for example, quartz crystal oscillators, radio transmitters, and receivers, cell phones, and electronic watches and clocks. Quartz crystal oscillators are used as timing references for computers, precision measurement equipment, navigation systems (GPS), and much more.

 Integrierter Quarzoszillator (smial)

Optical Fiber Communication

The technology of optical fiber communication has evolved from quartz fibers to glass fibers to plastic fibers. The earliest form of optical fiber communication made use of a very long piezoelectric quartz fiber that vibrated at the desired frequency. These vibrations were then transformed into light by exciting a small segment of the fiber with an electric current. Today's optical fibers are composed of glass or plastic.

Fiber Optic Cable Blue

Medical

 Quartz crystals are used in many medical applications such as sonogram machines, x-ray machines, and ultrasound machines; these crystals produce high-frequency sound waves that can penetrate soft tissue without damaging it. Piezoelectric materials also find application in surgical instruments such as scalpels. In these instruments, ultrasonic sound waves are focused on the surgical site which turns the water molecules into a cutting instrument.

X-ray machine-Arppeanum-DSC05413.

Microbalance

Another application of the piezoelectric effect is in the quartz crystal microbalance, which measures the mass per unit area by measuring the change in frequency of a quartz crystal resonator when there is a mass on its surface (due to capacitive coupling, it also works with liquids). In essence, the resonance frequency changes due to the addition or subtraction of an adatom layer to one side of the crystal.

Mettler Toledo ME30 Microbalance Balance

Conclusion

Without getting deep into details concerning the atomic structure of these crystals and the polarization of these ions, let's just say that piezoelectricity originates mainly from the polarization of oxygen ions in crystals under high temperatures. Under moderate temperatures, there are still enough free ions to allow for an electric current to pass through them and be driven by some external force. It is this intrinsic property of quartz crystal that makes it such a valuable material for certain applications requiring high levels of power. 


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