Robert Blinc
- Published in print:
- 2011
- Published Online:
- January 2012
- ISBN:
- 9780199570942
- eISBN:
- 9780191728631
- Item type:
- chapter
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/acprof:oso/9780199570942.003.0008
- Subject:
- Physics, Condensed Matter Physics / Materials
A theory of the electrocaloric effect is presented. It is shown that the electrocaloric effect in ferroelectrics is maximal at the electric‐field‐induced first‐order phase transition, whereas it is ...
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A theory of the electrocaloric effect is presented. It is shown that the electrocaloric effect in ferroelectrics is maximal at the electric‐field‐induced first‐order phase transition, whereas it is maximal in relaxors at the electric‐field‐induced critical end point. The maximum efficiencies ΔT/ΔE and ΔS/ΔE for various samples are presented. It is shown that in relaxors a giant electrocaloric effect takes place at the critical end point where also the electromechanical response is largest. A universal expression for the maximum temperature change in the saturation regime is derived that is valid both for electrocaloric and magnetocaloric systems.Less
A theory of the electrocaloric effect is presented. It is shown that the electrocaloric effect in ferroelectrics is maximal at the electric‐field‐induced first‐order phase transition, whereas it is maximal in relaxors at the electric‐field‐induced critical end point. The maximum efficiencies ΔT/ΔE and ΔS/ΔE for various samples are presented. It is shown that in relaxors a giant electrocaloric effect takes place at the critical end point where also the electromechanical response is largest. A universal expression for the maximum temperature change in the saturation regime is derived that is valid both for electrocaloric and magnetocaloric systems.
Robert Blinc
- Published in print:
- 2011
- Published Online:
- January 2012
- ISBN:
- 9780199570942
- eISBN:
- 9780191728631
- Item type:
- book
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/acprof:oso/9780199570942.001.0001
- Subject:
- Physics, Condensed Matter Physics / Materials
The field of ferroelectricity has greatly expanded and changed recently. In addition to classical organic and inorganic ferroelectrics as well as composite ferroelectrics new fields and materials ...
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The field of ferroelectricity has greatly expanded and changed recently. In addition to classical organic and inorganic ferroelectrics as well as composite ferroelectrics new fields and materials have appeared, important for both basic science and application and showing technological promise for novel multifunctional devices. Most of these fields were unknown or inactive 20 to 40 years ago. Such new fields are multiferroic magnetoelectric systems, where the spontaneous polarization and the spontaneous magnetization are allowed to coexist, incommensurate ferroelectrics, where the periodicity of the order parameter is incommensurate to the periodicity of the underlying basic crystal lattice, ferroelectric liquid crystals, dipolar glasses, relaxor ferroelectrics, ferroelectric thin films and nanoferroelectrics. These new fields are in addition to basic physical interest also of great technological importance and allow for new memory devices, spintronic applications and electro‐optic devices. They are also important for applications in acoustics, robotics, telecommunications and medicine. New developments in relaxors allow for giant electromechanical and electrocaloric effects. The book is primarily intended for material scientists working in research or industry. It is also intended for graduate and doctoral students and can be used as a textbook in graduate courses. Finally, it should be useful for everybody following the development of modern solid‐state physics.Less
The field of ferroelectricity has greatly expanded and changed recently. In addition to classical organic and inorganic ferroelectrics as well as composite ferroelectrics new fields and materials have appeared, important for both basic science and application and showing technological promise for novel multifunctional devices. Most of these fields were unknown or inactive 20 to 40 years ago. Such new fields are multiferroic magnetoelectric systems, where the spontaneous polarization and the spontaneous magnetization are allowed to coexist, incommensurate ferroelectrics, where the periodicity of the order parameter is incommensurate to the periodicity of the underlying basic crystal lattice, ferroelectric liquid crystals, dipolar glasses, relaxor ferroelectrics, ferroelectric thin films and nanoferroelectrics. These new fields are in addition to basic physical interest also of great technological importance and allow for new memory devices, spintronic applications and electro‐optic devices. They are also important for applications in acoustics, robotics, telecommunications and medicine. New developments in relaxors allow for giant electromechanical and electrocaloric effects. The book is primarily intended for material scientists working in research or industry. It is also intended for graduate and doctoral students and can be used as a textbook in graduate courses. Finally, it should be useful for everybody following the development of modern solid‐state physics.
Robert E. Newnham
- Published in print:
- 2004
- Published Online:
- November 2020
- ISBN:
- 9780198520757
- eISBN:
- 9780191916601
- Item type:
- chapter
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/oso/9780198520757.003.0009
- Subject:
- Earth Sciences and Geography, Geochemistry
Before beginning the discussion of directional properties, we pause to consider specific heat, an important scalar property of solids which helps illustrate the ...
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Before beginning the discussion of directional properties, we pause to consider specific heat, an important scalar property of solids which helps illustrate the important thermodynamic relationships between measured properties. Heat capacity, compressibility, and volume expansivity are interrelated through the laws of thermodynamics. Based on these ideas, similar relationships are established for other electrical, thermal, mechanical, and magnetic properties. Several atomistic concepts are introduced to help understand the structure–property relationships involved in specific heat measurements. The heat capacity or specific heat is the amount of heat required to raise the temperature of a solid by 1K. It is usually measured in units of J/kg K. Theorists prefer to work in J/mole K, and older scientists sometimes use calories rather than joules. One calorie is 4.186 J. For solids and liquids, the specific heat is normally measured at a constant pressure: where ΔQ is the heat added to increase the temperature by ΔT. Measurements on gases are usually carried out at constant volume: Electrical methods are generally employed in measuring specific heat. A heating coil is wrapped around the sample and the resulting change in temperature is measured with a thermocouple. If a current I flows through a wire of resistance R, the heat generated by the wire in a time Δt is given by . . . ΔQ = I2R
Less
Before beginning the discussion of directional properties, we pause to consider specific heat, an important scalar property of solids which helps illustrate the important thermodynamic relationships between measured properties. Heat capacity, compressibility, and volume expansivity are interrelated through the laws of thermodynamics. Based on these ideas, similar relationships are established for other electrical, thermal, mechanical, and magnetic properties. Several atomistic concepts are introduced to help understand the structure–property relationships involved in specific heat measurements. The heat capacity or specific heat is the amount of heat required to raise the temperature of a solid by 1K. It is usually measured in units of J/kg K. Theorists prefer to work in J/mole K, and older scientists sometimes use calories rather than joules. One calorie is 4.186 J. For solids and liquids, the specific heat is normally measured at a constant pressure: where ΔQ is the heat added to increase the temperature by ΔT. Measurements on gases are usually carried out at constant volume: Electrical methods are generally employed in measuring specific heat. A heating coil is wrapped around the sample and the resulting change in temperature is measured with a thermocouple. If a current I flows through a wire of resistance R, the heat generated by the wire in a time Δt is given by . . . ΔQ = I2R
