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Section 4.3 describes the Dielectric Loss and Loss Angle.Section 4.4 describes the piezoelectric material and Quartz CrystaL Oscillator.

Section 4.3. Dielectric Loss.

Theoretically the dielectric constant is real and a capacitor having a dielectric separation of plates always causes a 90° Leading Current with respect to the applied voltage hence loss is zero and an ideal capacitor is always a conservative system. But as we have seen that dissipative absorption can take place at higher frequencies. The relative permittivity at alternating frequency is lower than DC relative permittivity and relative permittivity becomes complex at frequencies where loss occurs.

Thermal agitation tries to randomize the dipole orientations whereas the applied alternating field tries to align the dipole moment along the alternating field. In process of this alignment there is inevitable loss of electric energy. This loss is known as Dielectric Loss. The absorption of electrical energy by a dielectric material subjected to alternating Electric Field is termed as Dielectric Loss.

The real part is the Relative Permittivity and the imaginary part is the Energy Loss part. Because of Complex Relative Permittivity a loss angle (δ) is introduced.

4.3.1. Loss Angle (δ).

Parallel plate capacitor is given as follows:

To account for the lossy nature of the dielectric we assume complex relative permittivity. Hence we get:

Real part of the Capacitance causes Quadrature Component and Imaginary Part causes In-Phase component. The In-phase component causes the loss angle hence loss angle is defined as:

In the Table 4.3.1.we tabulate some important dielectrics and their loss Tangents. In Figure 4.4 the Relative Permittivity Real Part and Imaginary Part is plotted as frequency.

Table 4.3.1. Some important dielectrics and their loss angle tangent.

Ceramics Tan (δ) Dielectric Strength Applications
Air 0 31.7kV/cm at 60 Hz Tested in 1cm gap
Al 2 O 3 0.002 to 0.01
SiO 2 0.00038 10MV/cm at DC IC Technology MOSFET
BaTiO 3 0.0001 to 0.02
Mica 0.0016
Polystrene 0.0001 Low loss Capacitance
Polypropylene 0.0002 Low loss Capacitance
SF 6 Gas 79.3kV/cm at 60 Hz Used in High Voltage Circuit BreaakersTo avoid discharge
Polybutane >138kV/cm at 60 Hz Liquid dielectric in cable filler
Transformar Oil 128kV/cm at 60 Hz
Borosilacate Glass 10MV/cm duration 10μs6MV/cm duration 30s

As seen in Figure 4.4, there is significant loss at low frequency, at Radio-Wave frequency, at Infra-Red frequency and at Ultra-Violet frequency. These correspond to the natural frequencies of the electron cloud system shown in Figure 4.3. For High-Q systems we require capacitance with dielectric material having a very low loss angle. These are generally Poly-sterene Capacitances or Poly-propylene Capacitors.

Section 4.4. Piezoelectric Effect and Piezoelectric Materials.

Electricity resulting from Pressure is known as piezo-electricity. This is called piezo-electric effect.

Electricity causes deformation of such materials. This is known as inverse piezo-electric effect. The most commonly used piezo-electric materials are Quartz, Rochelle Salts, Sodium Potassium Tartarate and tourmaline.

Rochelle Salts are mechanically weak but electrically very sensitive. Hence used in micro-phones, heads-phones and loud speakers.

Tourmaline are mechanically the strongest but electrically least sensitive. At frequencies higher than 100MHz, vibrational breakage can take place hence mechanically strongest materials are used namely Tourmaline.

Quartz Wafers are very popular as the stab lest electronic oscillators. These are known as Quartz Crystal Oscillators and to date these are stab lest with only 1part in million drift due to temperature, aging or load. Recently MEMS oscillators have proved to be even more stable. In Quartz Crystal Oscillators, Quartz mechanically oscillates but because of its piezo-electric property it behaves like a LC Tank-circuit with a very high Q Factor. Hence it allows the electronic oscillator to oscillate at its Resonance Frequencies which are critically dependent on the Physical Dimensions. Hence as long as Physical Dimensions are accurately reproduced so long the requisite Oscillation Frequency is accurately generated. The resonance frequencies of some of the standard cut Quartz Wafers are given in Table 4.4.1.

Table 4.4.1. Resonance frequencies and the Q-Factor of standard cut Quartz Wafers.

Frequecy(Hz) 32k 280k 525k 2M 10M
R S (Ω) 40k 1820 1400 82 5
L S (H) 4800 25.9 12.7 0.52 12mH
C s (pF) 0.0491 0.0126 0.00724 0.0122 0.0145
C p (pF) 2.85 5.62 3.44 4.27 4.35
Q Factor 25,000 25,000 30,000 80,000 150,000

The electrical analog of the mechanical vibration of Quartz Crystal is as follows:

Electrical Analog of the Mass of the Quartz Wafer is L S .

Electrical Analog of the spring constant of the Quartz Wafer is C S .

Electrical Analog of the damping of the Quartz Wafer is R S .

C P is the parallel electrode capacitance.

L S , C S , R S comprises the intrinsic series resonance path and C P is in parallel with this Series Resonance Path as shown in Figure 4.5.

Questions & Answers

what is the stm
Brian Reply
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industrial application...? mmm I think on the medical side as drug carrier, but you should go deeper on your research, I may be wrong
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what is simplest way to understand the applications of nano robots used to detect the cancer affected cell of human body.? How this robot is carried to required site of body cell.? what will be the carrier material and how can be detected that correct delivery of drug is done Rafiq
what is Nano technology ?
Bob Reply
write examples of Nano molecule?
The nanotechnology is as new science, to scale nanometric
nanotechnology is the study, desing, synthesis, manipulation and application of materials and functional systems through control of matter at nanoscale
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Damian Reply
what king of growth are you checking .?
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Stoney Reply
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yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
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sciencedirect big data base
Introduction about quantum dots in nanotechnology
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what does nano mean?
Anassong Reply
nano basically means 10^(-9). nanometer is a unit to measure length.
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s. Reply
there is no specific books for beginners but there is book called principle of nanotechnology
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Devang Reply
are you nano engineer ?
fullerene is a bucky ball aka Carbon 60 molecule. It was name by the architect Fuller. He design the geodesic dome. it resembles a soccer ball.
what is the actual application of fullerenes nowadays?
That is a great question Damian. best way to answer that question is to Google it. there are hundreds of applications for buck minister fullerenes, from medical to aerospace. you can also find plenty of research papers that will give you great detail on the potential applications of fullerenes.
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Source:  OpenStax, Electrical and electronic materials science. OpenStax CNX. May 01, 2014 Download for free at http://cnx.org/content/col11615/1.14
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