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Electronic Properties of Perovskite Oxides
Published in Gibin George, Sivasankara Rao Ede, Zhiping Luo, Fundamentals of Perovskite Oxides, 2020
Gibin George, Sivasankara Rao Ede, Zhiping Luo
Perovskite materials are best known for their dielectric properties. Materials with high dielectric strength and low dielectric loss are ideal candidates for capacitors and insulators. Dielectric materials are insulator materials that undergo polarization in the presence of an electric field (Figure 6.16). Even though dielectric materials are insulators, the term dielectric represents the ability of a material to store energy by means of polarization. Under the application of an external field, the positive charges of the dielectric materials are aligned towards the direction of the field and negative charges away from the field. Many perovskites are identified as excellent dielectric materials, and often the dielectric materials exhibit piezoelectric characteristics and the associated properties like pyroelectric properties.
Heat transfer applications of lossy TLM algorithms
Published in Donard de Cogan, Transmission Line Matrix (TLM) Techniques for Diffusion Applications, 2018
Electromagnetic energy leads to heating through dielectric losses. This appears in the expression for relative permittivity: εr=ε′−jε″(where j=−1)
Applications
Published in Raj P. Chhabra, CRC Handbook of Thermal Engineering Second Edition, 2017
Joshua D. Ramsey, Ken Bell, Ramesh K. Shah, Bengt Sundén, Zan Wu, Clement Kleinstreuer, Zelin Xu, D. Ian Wilson, Graham T. Polley, John A. Pearce, Kenneth R. Diller, Jonathan W. Valvano, David W. Yarbrough, Moncef Krarti, John Zhai, Jan Kośny, Christian K. Bach, Ian H. Bell, Craig R. Bradshaw, Eckhard A. Groll, Abhinav Krishna, Orkan Kurtulus, Margaret M. Mathison, Bryce Shaffer, Bin Yang, Xinye Zhang, Davide Ziviani, Robert F. Boehm, Anthony F. Mills, Santanu Bandyopadhyay, Shankar Narasimhan, Donald L. Fenton, Raj M. Manglik, Sameer Khandekar, Mario F. Trujillo, Rolf D. Reitz, Milind A. Jog, Prabhat Kumar, K.P. Sandeep, Sanjiv Sinha, Krishna Valavala, Jun Ma, Pradeep Lall, Harold R. Jacobs, Mangesh Chaudhari, Amit Agrawal, Robert J. Moffat, Tadhg O’Donovan, Jungho Kim, S.A. Sherif, Alan T. McDonald, Arturo Pacheco-Vega, Gerardo Diaz, Mihir Sen, K.T. Yang, Martine Rueff, Evelyne Mauret, Pawel Wawrzyniak, Ireneusz Zbicinski, Mariia Sobulska, P.S. Ghoshdastidar, Naveen Tiwari, Rajappa Tadepalli, Raj Ganesh S. Pala, Desh Bandhu Singh, G. N. Tiwari
Dielectric properties consist of dielectric constant (ε′) and dielectric loss factor (ε″). Dielectric constant is a measure of the ability of a material to store electromagnetic energy, whereas dielectric loss factor is a measure of the ability of a material to convert electromagnetic energy to heat (Metaxas and Meredith, 1983). Dielectric constant and dielectric loss factor can be defined in terms of complex permittivity (ε). The complex permittivity (ε) is composed of a real part (ε′, relative dielectric constant) and an imaginary part (ε″, effective relative dielectric loss factor) and is given by the following equation (Saltiel and Datta, 1999):
Structural, dielectric, electrical, and optical properties of the Ca3CuTi4O12 ceramic
Published in Phase Transitions, 2022
S. K. Parida, Prativa Pattnaik, S. Mishra, R. N. P. Choudhary
Figure 13 (a, b) shows the variation of tanδ with frequency and temperature respectively. The formation of dielectric peaks at higher temperatures in Figure 13 (a) suggests the presence of a non-Debye type of relation mechanism in the studied material. The origin of the dielectric loss in the dielectric materials comes from three factors: direct current, movement of dipole and space charge migration [53]. The theory of dielectric loss (tanδ) is related to the dielectric relaxation mechanism and can be defined as the ratio of the complex component () to real component of permittivity () i.e. tanδ =. The value of the dielectric loss is the energy loss and that occurs when the polarization lags behind the external applied electric field that caused by the effect of grain boundaries. At low frequency, higher value of the dielectric loss can be attributed to the high resistivity of the grain boundaries; which are more effective than that of grains.
Microwave absorption properties of organic sulfur compounds in coal: application of desulfurization
Published in Journal of Sulfur Chemistry, 2021
Tao Ge, Chuanchuan Cai, Mingxu Zhang
Dielectric loss is the physical process of converting a portion of electrical energy into thermal energy by a medium. The real part of the complex dielectric constant is related to dielectric polarization and energy loss [27]. In contrast, the imaginary part of the complex dielectric constant characterizes the ability to convert electrical energy into thermal energy [28]. As shown in Figure 4(a), the real part of complex dielectric constants of organic sulfur compounds had a little change with the increasing microwave frequency. The influence of microwave frequency on the real part of a medium's complex dielectric constants is related to polarization mechanism, which can be classified in four ways: displacement polarization, relaxed polarization, orientation polarization, space charge polarization [38]. The formation of various polarizations takes a certain amount of time. At low frequencies, such as 2.0–8.0 GHz, electron relaxation polarization only occurs in compounds generally since the long polarization time required [27].
Dielectric characterization of bentonite clay at various moisture contents and with mixtures of biomass in the microwave spectrum
Published in Journal of Microwave Power and Electromagnetic Energy, 2018
Candice Ellison, Murat Sean McKeown, Samir Trabelsi, Cosmin Marculescu, Dorin Boldor
In order to effectively utilize microwave heating for pyrolysis, it is important to understand the coupling of microwaves with the dielectric material to be heated by measurement of material dielectric properties. In the case of organic materials, such as biomass feedstocks used for pyrolysis, both dipole and ionic polarization occur at microwave frequencies; water in the material undergoes dipole polarization, while the electric potential of membranes within cells of biological tissue undergo ionic polarization (Torgovnikov 1993). Thus, the water content and composition of the material are important factors in the coupling of microwave energy with biomass materials. Dielectric properties are commonly described by the complex relative permittivity, which is expressed by , where the dielectric constant () is the real part, the dielectric loss factor () is the imaginary part and (Meredith 1998). The dielectric constant describes the ability of the material to store energy and the dielectric loss factor describes the ability of the material to dissipate energy.