Method for adjusting thermal expansion based on relaxation ferroelectric phase-transition electric fields

A technology of electric field regulation and ferroelectric phase, applied in the field of electric field regulation of thermal expansion behavior based on relaxor ferroelectric phase transition, and electric field regulation of thermal expansion behavior, which can solve problems such as shortening component life and accelerating material failure, and achieve the effect of avoiding thermal stress.

Inactive Publication Date: 2013-04-03
XI AN JIAOTONG UNIV
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

But the composite method can cause localized stresses that accelerate the failure of the material and ultimately shorten the life of the component

Method used

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  • Method for adjusting thermal expansion based on relaxation ferroelectric phase-transition electric fields
  • Method for adjusting thermal expansion based on relaxation ferroelectric phase-transition electric fields

Examples

Experimental program
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Effect test

Embodiment 1

[0030] (1) Select Pb(Zr 0.4 Ti 0.6 )O 3 As a matrix ferroelectric material, it undergoes a cubic (paraelectric phase) to tetragonal (ferroelectric phase) ferroelectric phase transition during cooling, accompanied by volume expansion of the material.

[0031] (2) La is selected as the doping element instead of Pb to form La-substituted Pb-type point defects. Materials with different La content (Pb 1-x La x )(Zr 0.4 Ti 0.6 )O 3 . Dielectric performance tests show that with the increase of La content, the ferroelectric phase transition temperature from cubic (paraelectric phase) to tetragonal (ferroelectric phase) decreases sharply. When the La content exceeds its critical value (16%), the ferroelectric phase transition is completely suppressed, and the material undergoes a relaxation ferroelectric phase transition.

[0032] (3) The in-situ transmission electron microscopy test during the cooling process showed that (Pb 0.83 La 0.17 )(Zr 0.4 Ti 0.6 )O 3 A part of th...

Embodiment 2

[0035] (1) Select PbTiO 3 (abbreviated as PT) is a matrix ferroelectric material, which undergoes a cubic (paraelectric phase) to tetragonal (ferroelectric phase) ferroelectric phase transition during cooling, accompanied by volume expansion of the material.

[0036] (2) Select Pb(Mg 1 / 3 Nb 2 / 3 )O 3 (PMN for short) as doping, with PbTiO 3 The matrix mixes, forming defects. Materials with different PMN contents (xPMN-(1-x)PT) were prepared by solid-state sintering. Dielectric property tests show that with the increase of PMN content, the ferroelectric phase transition temperature from cubic (paraelectric phase) to tetragonal (ferroelectric phase) decreases sharply. When the PMN content exceeds its critical value (70%), the ferroelectric phase transition is completely suppressed, and the material undergoes a relaxation ferroelectric phase transition.

[0037](3) The in-situ transmission electron microscopy test during the cooling process shows that a part of the high-tempe...

Embodiment 3

[0040] (1) Choose BaTiO 3 As a matrix ferroelectric material, it undergoes a cubic (paraelectric phase) to tetragonal (ferroelectric phase) ferroelectric phase transition during cooling, accompanied by volume expansion of the material.

[0041] (2) Select Sn as the doping element instead of Ti to form Sn-substituted Ti-type point defects. Materials with different Sn contents Ba(Ti 1-x sn x )O 3 . Dielectric property tests show that the cubic-to-tetragonal ferroelectric phase transition gradually disappears with increasing Sn content. When the Sn content exceeds its critical value (19%), the ferroelectric phase transition is completely suppressed, and the material undergoes a relaxation ferroelectric phase transition.

[0042] (3) In situ transmission electron microscope test during the cooling process showed that Ba(Ti 0.8 sn 0.2 )O 3 A part of the high-temperature paraelectric phase in the material transforms into nanometer-sized ferroelectric domains (triclinic), and...

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Abstract

The invention discloses a method for adjusting thermal expansion based on relaxation ferroelectric phase-transition electric fields. The method comprises the following steps of: selecting a ferroelectric phase-transition base ferroelectric material which can cause volume expansion in a cooling process, and doping defects; enabling the material to generate relaxation ferroelectric phase transition when the doping concentration exceeds a critical value; transferring one part of high-temperature paraelectric phases to nanometer ferroelectric domains to generate volume expansion; enabling the structure of the remaining part not to change, and reducing the volume in the cooling process; applying electric fields to the relaxation ferroelectric material, so that the quantity and size of the nanometer ferroelectric domains are increased with the increase of the externally applied electric fields, and the volume expansion effect caused by the nanometer ferroelectric domains is also increased; conversely, gradually reducing the volume shrinkage effect of the base body without structural changes. Therefore, the volume fraction of the nanometer ferroelectric domains in the material is adjusted by changing the externally-applied electric fields to regulate the proportion of the volume expansion effect and the volume shrinkage effect, so that the integral thermal expansion of the material is realized.

Description

technical field [0001] The invention belongs to the technical field of ferroelectric materials, and relates to a method for regulating thermal expansion behavior by an electric field, in particular to a method for regulating thermal expansion behavior by an electric field based on a relaxation ferroelectric phase transition. Background technique [0002] Thermal expansion and contraction is a common phenomenon that exists widely in nature, and it is also an important problem faced by many fields such as machinery, electronics, and optics. Because the amplitude of the anharmonic vibration of atoms, ions, and molecules that make up the material will increase with the rise of temperature, most materials will expand in volume during the heating process. This phenomenon is known as positive thermal expansion. When a material is heated, its linear dimensions increase approximately proportional to the temperature. As the temperature changes, the length of the material changes by:...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C04B35/491C04B35/499C04B35/468C04B35/457C04B35/48C04B35/50
Inventor 孙军丁向东周玉美薛德祯任晓兵
Owner XI AN JIAOTONG UNIV
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