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A method and device for controlling ferroelectric crystal domains

A ferroelectric crystal and electric domain technology, which is applied in the field of preparation of ferroelectric materials, can solve the problems of inability to accurately control the morphology and size of electric domains, reduce piezoelectric constants, limit high-voltage electric effects, etc., and achieve good piezoelectricity. Effects of thermal stability, enhanced piezoelectric effect, and improved polarization efficiency

Active Publication Date: 2020-01-17
XIAN TECH UNIV
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

Practice has found that this method has the following disadvantages: 1. For some crystals with large-scale electric domain structures, the external electric field will induce electric domain inversion, and the stress cannot be released quickly during the inversion process. Therefore, using the traditional polarization method, Microcracks caused by internal stress are easy to occur inside the crystal; 2. The crystal electric domain structure is closely related to the crystal symmetry, and there are at least eight crystal shapes in the crystal with low symmetry, and the electric domain size and shape are relatively random , the traditional polarization method can only adjust the macroscopic domain morphology and piezoelectric properties, but cannot accurately control the local domain size and piezoelectric properties; 3. Theoretical calculations show that the piezoelectric constant will increase with temperature, and It reaches the highest at the phase transition point, and the piezoelectric constant decreases sharply when the temperature rises
For ferroelectric crystals prepared by traditional polarization methods, when the external temperature rises above the polarization temperature, the piezoelectric constant decreases rapidly to zero, and the temperature stability is poor; 4. The piezoelectric effect of ferroelectric crystals is the same as the internal domain structure of the crystals. Closely related, the traditional polarization method cannot accurately control the morphology and size of the electric domain, which limits the realization of the piezoelectric effect

Method used

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  • A method and device for controlling ferroelectric crystal domains
  • A method and device for controlling ferroelectric crystal domains
  • A method and device for controlling ferroelectric crystal domains

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0042] Embodiment 1: multi-domain PMN-PT crystal

[0043] Crystal sample size: 3mmх3mmх15mm, phase structure at room temperature: tetragonal phase, crystal orientation: [111], electric domain observation direction: [111].

[0044] Polarization process:

[0045] Step 1. Use the fixture module to fix the PMN-PT crystal sample, then place the fixture in a temperature-controlled furnace, raise the temperature to 210 degrees, the temperature control accuracy is 0.1 degrees, and the holding time is 10 minutes;

[0046] Step 2. Apply an electric field with a voltage intensity of 12 V / mm and a current of 1 mA along the direction perpendicular to the electrodes, and keep it for 10 minutes;

[0047] Step 3. Lower the temperature at a rate of 0.5 degrees per minute, and increase the voltage intensity at the same time so that it is always above twice the coercive field. The current value is kept at 1 mA; when the temperature drops to 100 degrees, keep it warm for 5 minutes. It is 300 vo...

Embodiment 2

[0049] Embodiment 2: Monodomain PMN-PT crystal

[0050] Crystal sample size: 3mmх3mmх15mm, phase structure at room temperature: tetragonal phase, crystal orientation: [001] and [100], electric domain observation direction: [001].

[0051] Polarization process:

[0052] Step 1. Use the fixture module to fix the PMN-PT crystal sample, then place the fixture in a temperature-controlled furnace, heat up to 200 degrees, the temperature control accuracy is 0.1 degrees, and the holding time is 20 minutes;

[0053] Step 2. Apply an electric field with a voltage intensity of 12 V / mm and a current of 1 mA along the direction perpendicular to the electrodes, and keep it for 10 minutes;

[0054] Step 3. Lower the temperature at a rate of 1.0 degrees per minute, and at the same time increase the voltage intensity so that it is always above twice the coercive field and keep the current value at 1 mA; when the temperature drops to 150 degrees, keep it warm for 5 minutes. 50 volts / mm; when ...

Embodiment 3

[0056] Embodiment 3: Multi-domain PIN-PMN-PT crystal

[0057] Crystal sample size: 3mmх3mmх15mm, phase structure at room temperature: tetragonal phase, crystal orientation: [111], electric domain observation direction: [111].

[0058] Polarization process:

[0059] Step 1. Use the fixture module to fix the PIN-PMN-PT crystal sample, then place the fixture in a temperature-controlled furnace, raise the temperature to 300 degrees, the temperature control accuracy is 0.1 degrees, and the holding time is 20 minutes;

[0060] Step 2. Apply an electric field with a voltage intensity of 15 V / mm and a current of 1 mA along the direction perpendicular to the electrodes, and keep it for 20 minutes;

[0061] Step 3. Lower the temperature at a rate of 1.0 degrees per minute, and at the same time increase the voltage intensity so that it is always above twice the coercive field and keep the current value at 1 mA; when the temperature drops to 200 degrees, keep it warm for 5 minutes. 90 v...

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Abstract

The invention relates to a method and device for controlling electric domain of a ferroelectric crystal. The method for controlling the electric domain of the ferroelectric crystal sequentially comprises the following steps: firstly, increasing temperature of a ferroelectric crystal to a range from more than 200 DEG C above a phase-transition temperature to 1000 DEG C, and carrying out heat preservation for 10-20 minutes; secondly, applying voltage with intensity more than two times that of a coercive field along the direction vertical to an electrode, controlling current to be 1-3mA, and maintaining for 10-20 minutes; thirdly, cooling at a speed less than 2 DEG C / minute, adjusting intensity of an outlaid electric field, so that the intensity is more than two times that of the coercive field all the time, and finally cooling to room temperature. The device for controlling the electric domain of the ferroelectric crystal comprises a high precision temperature control furnace, a high precision linear current and voltage source, a system protection circuit and a fixture module arranged in the high precision temperature control furnace. The method and device for controlling the electric domain of the ferroelectric crystal have the advantages that the problem that microcracks occur inside a domain engineering ferroelectric crystal is solved, electric domain dimension is accurately controlled and reduced, temperature stability is improved, and finally piezoelectric effect of the ferroelectric crystal is effectively improved.

Description

technical field [0001] The invention relates to the technical field of preparation of ferroelectric materials, in particular to a method and device for controlling electric domains of ferroelectric crystals. Background technique [0002] Ferroelectric materials have been used in medical ultrasonic transducers, underwater acoustic transducers, drives, ultrasonic motors, pyroelectric devices, precision displacement control devices, and energy harvesting. Ferroelectric domains are an essential feature of ferroelectric materials, which can be reoriented by an external electric field and split into a series of regions with the same spontaneous polarization direction. The domain morphology and size of the crystal are not only related to the material itself, but also affected by the external electric field and temperature. In addition, the domain size is also related to the crystal size. Polarize along the crystal direction parallel to the spontaneous polarization direction to obt...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): C21D10/00
Inventor 林大斌周顺刘欢蔡长龙刘卫国
Owner XIAN TECH UNIV
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