阅读说明：本技术 一种杂化非本征铁电体Ca3Ti2O7及其掺杂化合物的应用 (Hybrid extrinsic ferroelectric Ca3Ti2O7 and application of doped compound thereof ) 是由 王守宇 陈畅 刘卫芳 张雄南 江瑶 于 2019-12-19 设计创作，主要内容包括：本发明提供了一种杂化非本征铁电体Ca<Sub>3</Sub>Ti<Sub>2</Sub>O<Sub>7</Sub>及其掺杂化合物在铁电存储器中的应用,涉及压电材料技术领域。本发明提供的杂化非本征铁电体Ca<Sub>3</Sub>Ti<Sub>2</Sub>O<Sub>7</Sub>及其掺杂化合物在铁电存储器中的应用,所述Ca<Sub>3</Sub>Ti<Sub>2</Sub>O<Sub>7</Sub>及其掺杂化合物具有负压电性。杂化非本征铁电体Ca<Sub>3</Sub>Ti<Sub>2</Sub>O<Sub>7</Sub>及其掺杂化合物具有负压电性,将其与正压电性材料结合后制作的铁电存储器的有效元件,具有无电场引起应力的优点,使器件整体不表现出压电效应,大大增强了器件的抗疲劳性,延长了铁电存储器的寿命。(The invention provides a hybrid extrinsic ferroelectric Ca 3 Ti 2 O 7 And the application of the doped compound in ferroelectric memory, relating to the technical field of piezoelectric materials. The invention provides a hybrid extrinsic ferroelectric Ca 3 Ti 2 O 7 And their use as doping compounds in ferroelectric memories, the Ca 3 Ti 2 O 7 And the doped compound thereof has negative piezoelectric property. Hybrid extrinsic ferroelectric Ca 3 Ti 2 O 7 The doped compound has negative voltage electrical property, and the effective element of the ferroelectric memory manufactured by combining the doped compound with the positive voltage electrical material has the advantage of no stress caused by an electric field, so that the whole device does not show the piezoelectric effect, the fatigue resistance of the device is greatly enhanced, and the service life of the ferroelectric memory is prolonged。)

1. Hybrid extrinsic ferroelectric Ca₃Ti₂O₇And the use of their doping compounds for the production of ferroelectric memories, characterized in that the Ca is present₃Ti₂O₇And the doped compound thereof has negative piezoelectric property.

2. Use according to claim 1, wherein the doping compound comprises a Na ion doped compound or a Li ion doped compound.

3. Use according to claim 1, wherein the Na ion-doped compound has the formula Ca_2.9Na_0.1Ti₂O₇。

4. Hybrid extrinsic ferroelectric Ca₃Ti₂O₇And the application of the doped compound in the preparation of sensors.

5. Use according to claim 4, wherein the sensor comprises a piezoelectric sensor.

6. Hybrid extrinsic ferroelectric Ca₃Ti₂O₇And the use of doped compounds thereof for the production of actuators.

7. Use according to claim 6, wherein the actuator comprises a piezoelectric actuator or a micro-ceramic actuator.

Technical Field

The invention relates to the technical field of piezoelectric materials, in particular to a hybrid extrinsic ferroelectric Ca₃Ti₂O₇And the use of doped compounds thereof.

Background

Piezoelectricity is the property of a dielectric that polarizes under pressure to create a potential difference between its two end surfaces. In 1880, when P.Curie and J.Curie brothers found that a quartz crystal is stressed, electric charges can be generated on certain surfaces of the quartz crystal, the electric charge quantity is in direct proportion to the stress, and the phenomenon is called as a piezoelectric effect; an object having a piezoelectric effect is called a piezoelectric body. The curie brothers also demonstrate the inverse piezoelectric effect of the piezoelectric, i.e., the piezoelectric deforms under the action of an external electric field. The inverse piezoelectric effect is not equal to the negative piezoelectric effect, which means that the piezoelectric constant of the piezoelectric material with negative piezoelectric property is negative, and is opposite to the positive piezoelectric material. Most piezoelectric materials are positive piezoelectric materials.

The piezoelectric constant is a conversion coefficient of a piezoelectric body converting mechanical energy into electric energy or converting electric energy into mechanical energy, and reflects a coupling relation between elastic (mechanical) properties and dielectric properties of a piezoelectric material. By selecting different independent variables (or selecting different boundary conditions during measurement), four groups of piezoelectric constants d, g, e and h can be obtained, wherein the piezoelectric constant d is more commonly used. The piezoelectric constant d33 is one of the most common important parameters for characterizing the performance of piezoelectric materials, and generally, the higher the piezoelectric constant of ceramics is, the better the piezoelectric performance is. The first number in the subscripts refers to the direction of the electric field, the second to the direction of the stress or strain, "33" indicates that the polarization direction is the same as the direction of the applied force at the time of measurement.

The difference between the material with negative pressure electric property and the material with positive pressure electric property is: when an external electric field is added to the material, when the polarization direction of the material is consistent with the direction of the external electric field, the positive piezoelectric material can extend in the direction of the added electric field, and the deformation quantity is the same as the direction of the electric field; when an external electric field is applied to the negative-voltage electric material, the negative-voltage electric material contracts in the direction of the electric field, and the deformation amount is opposite to the direction of the electric field.

Since the piezoelectric properties of ferroelectric single crystals, ceramics and thin films are much higher than those of other non-ferroelectric materials, the electromechanical properties of ferroelectric single crystals, ceramics and thin films have been widely studied. In thatTypical ferroelectric single crystals and ceramics such as (BaTiO) were observed in the experiments₃,BT)、Bi_0.9La_0.1FeO₃And (Bi)_1/2K_1/2)TiO₃Most of the ferroelectric materials show positive piezoelectricity, the crystal lattice expands along the direction of an external electric field, and the displacement-electric field intensity curve of the ferroelectric materials is in a w shape. As known, only two ferroelectrics are experimentally determined to have negative voltage electrical property at present, one is a ferroelectric polymer polyvinylidene fluoride (PVDF), and the other is a two-dimensional layered ferroelectric material CuInP₂S, their displacement-electric field intensity curve is "m" type.

The piezoelectric material has good fatigue resistance, fast response, good temperature stability and good stability over time. The piezoelectric effect of the piezoelectric crystal can be used for manufacturing a variable frequency oscillator with high stability and a filter with good selectivity, and can also be used for manufacturing a piezoelectric thickness meter and the like; the inverse piezoelectric effect of the piezoelectric material can be used to convert the electric energy into mechanical energy or mechanical motion, so as to produce the piezoelectric driver, and the piezoelectric driver can also be used for producing precise micro-displacement brakes.

Ferroelectric memory is a special art non-volatile memory in which when an electric field is applied to a ferroelectric crystal, the central atom is stopped in one low energy state along the electric field, whereas when the electric field is reversed and applied to the same ferroelectric transistor, the central atom moves in the crystal along the direction of the electric field and stops in another low energy state. A large number of central atoms move and couple in the crystal unit cell to form a ferroelectric domain, and the ferroelectric domain forms polarization charges under the action of an electric field. The polarization charge formed by the ferroelectric domain reversing under the electric field is higher, and the polarization charge formed by the ferroelectric domain not reversing under the electric field is lower, so that the binary stable state of the ferroelectric material can lead the ferroelectric to be used as a memory.

However, the conventional ferroelectric memory may cause fatigue of the device due to accumulated stress caused by the piezoelectric response bias, which affects the lifetime. Piezoelectricity may be a key factor in determining its potential for use in future information processing and storage areas. The ferroelectric material with negative piezoelectricity and the ferroelectric material with positive piezoelectricity are combined together, so that the ferroelectric memory with zero piezoelectricity can be manufactured. When the ferroelectric memory manufactured in the way works, the external electric field generated by electrifying can extend the positive piezoelectric material towards the electric field direction and contract the negative piezoelectric material towards the electric field direction, and the positive piezoelectric material and the negative piezoelectric material are offset to show no piezoelectric effect outwards. Therefore, the ferroelectric memory has no stress caused by piezoelectric effect, and the fatigue resistance and the service life of the ferroelectric memory element are greatly increased. Therefore, it is of great significance to find new piezoelectric materials for ferroelectric memories to solve the internal stress problem of ferroelectric memories.

Disclosure of Invention

The invention aims to provide a hybrid extrinsic ferroelectric Ca₃Ti₂O₇And the application of its doped compound, the invention finds out that the hybridized extrinsic ferroelectric Ca₃Ti₂O₇The doped compound has negative piezoelectric property, and the effective element of the ferroelectric memory manufactured by combining the doped compound with the positive piezoelectric material has the advantage of no stress caused by an electric field, so that the whole device does not show piezoelectric effect, the fatigue resistance of the device is greatly enhanced, and the service life of the ferroelectric memory is prolonged.

In order to achieve the above object, the present invention provides the following technical solutions:

the invention provides a hybrid extrinsic ferroelectric Ca₃Ti₂O₇And its doped compound in the preparation of ferroelectric memory, the Ca₃Ti₂O₇And the doped compound thereof has negative piezoelectric property.

Preferably, the doping compound includes a Na ion-doped compound or a Li ion-doped compound.

Preferably, the chemical formula of the Na ion-doped compound is Ca_2.9Na_0.1Ti₂O₇。

The invention provides a hybrid extrinsic ferroelectric Ca₃Ti₂O₇And the application of the doped compound in the preparation of sensors.

Preferably, the sensor comprises a piezoelectric sensor.

The invention provides a hybrid extrinsic ferroelectric Ca₃Ti₂O₇And the use of doped compounds thereof for the production of actuators.

Preferably, the actuator comprises a piezoelectric displacement actuator or a micro-ceramic actuator.

The invention provides a hybrid extrinsic ferroelectric Ca₃Ti₂O₇And the application of its doped compound, the invention finds out that the hybridized extrinsic ferroelectric Ca₃Ti₂O₇And a doping compound thereof has negative pressure conductivity, and Ca having negative pressure conductivity is used₃Ti₂O₇The effective element of the ferroelectric memory manufactured by combining the positive piezoelectric material has the advantage of no stress caused by an electric field, so that the whole device does not show piezoelectric property, the fatigue resistance of the device is greatly enhanced, and the service life of the ferroelectric memory is prolonged.

Ca found in the present invention₃Ti₂O₇The material is simple to manufacture, does not contain harmful heavy metals such as lead and the like, and is environment-friendly and pollution-free.

Drawings

Fig. 1 is a schematic view of the displacement change of a positive piezoelectric material and a negative piezoelectric material under an electric field, wherein (a) represents the negative piezoelectric material, and (b) represents the positive piezoelectric material;

FIG. 2 shows Ca prepared in examples 1 and 2₃Ti₂O₇And Ca_2.9Na_0.1Ti₂O₇With standard Ca₃Ti₂O₇And Ca_2.9Na_0.1Ti₂O₇Pattern contrast of diffraction peaks of (a);

FIG. 3 shows Ca prepared in example 1₃Ti₂O₇A schematic diagram of a crystal structure;

FIG. 4 shows Ca prepared in example 1₃Ti₂O₇Graph of electric polarization and current return;

FIG. 5 shows Ca prepared in examples 1 and 2₃Ti₂O₇And Ca_2.9Na_0.1Ti₂O₇The displacement of the material obtained by adding a 0.1Hz frequency driving electric field at room temperature changes with the electric field (D-E curve);

FIG. 6 shows the formula of Ca₃Ti₂O₇A schematic design diagram of a micro-displacement detection device made of materials as effective elements;

FIG. 7 shows Ca prepared in example 1₃Ti₂O₇Working principle diagram of the probe;

FIG. 8 shows Ca prepared in example 1₃Ti₂O₇And ferroelectric Bi with positive piezoelectric property₄Ti₃O₁₂The effective memory element design of the combined zero-stress ferroelectric memory is schematic.

Detailed Description

The invention provides a hybrid extrinsic ferroelectric Ca₃Ti₂O₇And its doped compound in the preparation of ferroelectric memory, the Ca₃Ti₂O₇And the doped compound thereof has negative piezoelectric property.

In the present invention, the doping compound is preferably a Na ion-doped compound or a Li ion-doped compound; the chemical formula of the Na ion-doped compound is preferably Ca_2.9Na_0.1Ti₂O₇。

The invention relates to the hybrid extrinsic ferroelectric Ca₃Ti₂O₇The source of the dopant compound is not particularly limited, and the dopant compound can be prepared by a method known in the art. In the examples of the present invention, the hybrid extrinsic ferroelectric Ca₃Ti₂O₇The preparation method of the doped compound is preferably a solid-phase reaction method or a sol-gel method.

In the present invention, unless otherwise specified, all the starting materials required for the preparation are commercially available products well known to those skilled in the art.

When the solid phase reaction method is adopted, the hybridized extrinsic ferroelectric Ca₃Ti₂O₇The preparation method of (a) preferably comprises the steps of:

mixing a calcium source and a titanium source, and performing ball milling to obtain a mixed material;

performing first sintering on the mixed material to obtain a sintered material;

pressing the sintering material, and performing second sintering to obtain the hybrid extrinsic ferroelectric Ca₃Ti₂O₇。

The method mixes the calcium source and the titanium source, and ball-mills the mixture to obtain the mixed material. In the present invention, the calcium source is preferably calcium carbonate, the titanium source is preferably titanium dioxide, the purity of the calcium carbonate and the purity of the titanium dioxide are preferably 99.99%, and the molar ratio of the calcium source to the titanium source is preferably Ca₃Ti₂O₇I.e. 3: 2. According to the invention, alcohol is preferably added in the mixing process, so that the raw materials are uniformly mixed; the invention has no special limit on the dosage of the alcohol, and the raw materials can be uniformly mixed. In the invention, the time for ball milling is preferably 9-12 h, the ball milling is preferably carried out in a ball mill, the rotating speed of the ball milling is not particularly limited, and the raw materials can be uniformly mixed. After the ball milling is finished, the obtained material is preferably placed in a drying box to be dried by alcohol; the drying oven and the drying process are not particularly limited in the present invention, and the drying oven and the drying process well known in the art may be selected.

After the mixed material is obtained, the invention preferably performs first sintering on the mixed material to obtain a sintered material. In the invention, the first sintering is preferably carried out in a muffle furnace, the temperature of the first sintering is preferably 900-1100 ℃, more preferably 1000 ℃, the time is preferably 11-13 h, more preferably 12h, and the first sintering is preferably carried out in an air atmosphere.

After obtaining the sintering material, the invention preferably presses the sintering material, and then carries out secondary sintering to obtain the hybrid extrinsic ferroelectric Ca₃Ti₂O₇. In the invention, the pressing process is preferably to use a single-axis pressing die to make the sintered material into a wafer with the diameter of about 14mm and the thickness of 0.15-0.3 mm. In the invention, the temperature of the second sintering is preferably 1400-1600 ℃, more preferably 1500 ℃, the time of the second sintering is preferably 46-50 h, more preferably 48h, and the second sintering is preferably carried out in an air atmosphereAnd (6) rows. After the second sintering is finished, the mixture is cooled to room temperature along with the furnace to obtain the hybrid extrinsic ferroelectric Ca₃Ti₂O₇。

When the solid phase reaction method is adopted to prepare the hybridized extrinsic ferroelectric Ca₃Ti₂O₇When doping compound, the corresponding doping ion source is added into the raw material, and the dosage of the doping ion source is preferably Ca₃Ti₂O₇The stoichiometric ratio of the doping compounds can be calculated. Specifically, when preparing Ca doped with Na ions_2.9Na_0.1Ti₂O₇When the ceramic is selected, CaCO₃(99.99％)、TiO₂(99.99%) and Na₂CO₃(99.99%) in a stoichiometric ratio of 2.9:2:0.1, followed by mixing with the above-described hybrid extrinsic ferroelectric Ca₃Ti₂O₇The preparation process is the same, and is not described in detail herein.

When the sol-gel method is adopted, the hybridized extrinsic ferroelectric Ca₃Ti₂O₇The preparation method of (a) preferably comprises the steps of:

mixing calcium nitrate, butyl titanate, glycol and tartaric acid to obtain a mixed material;

carrying out sol-gel reaction on the mixed material to obtain gel;

sintering the gel to obtain the hybridized extrinsic ferroelectric Ca₃Ti₂O₇。

In the present invention, the calcium nitrate is preferably calcium nitrate tetrahydrate, and the purity of the calcium nitrate and butyl titanate is preferably 99.99%. In the present invention, the tetrabutyl titanate (Ti (OC)₄H₉)₄)、Ca(NO₃)₂·4H₂The molar ratio of O and tartaric acid is preferably 2:3: 5.

In the present invention, the mixing is preferably performed by dissolving calcium nitrate tetrahydrate and butyl titanate in ethylene glycol and then adding tartaric acid to the resulting solution. In the invention, the concentration of the calcium nitrate tetrahydrate and the tetrabutyl titanate in the solution obtained after dissolving in the ethylene glycol is preferably 0.5-0.8 mol/L independently, and more preferably 0.6-0.7 mol/L independently. The invention utilizes ethanol to mix the components more uniformly, and utilizes tartaric acid as a complexing agent.

In the invention, the sol-gel reaction process is preferably to stir the mixed material in a water bath at 50-100 ℃ for 4-6 hours until a clear and transparent solution is obtained; and then, placing the obtained solution in a drying oven, and drying at the temperature of 100-140 ℃ for 4-8 hours to obtain orange yellow gel.

In the invention, the sintering process is preferably to place the gel in a muffle furnace, heat the gel at 600-800 ℃ for about 5h, then place the gel in a sintering furnace, and sinter the gel at 1400-1600 ℃ for 48h to obtain the hybrid extrinsic ferroelectric Ca₃Ti₂O₇。

When the sol-gel method is adopted to prepare the hybridized extrinsic ferroelectric Ca₃Ti₂O₇When doping compound, the corresponding doping ion source is added into the raw material, and the dosage of the doping ion source is preferably Ca₃Ti₂O₇The stoichiometric ratio of the doping compounds can be calculated. Specifically, when preparing Ca doped with Na ions_2.9Na_0.1Ti₂O₇When the ceramic is selected, CaCO₃(99.99％)、TiO₂(99.99%) and Na₂CO₃(99.99%) in a stoichiometric ratio of 2.9:2:0.1, followed by mixing with the above-described hybrid extrinsic ferroelectric Ca₃Ti₂O₇The preparation process is the same, and is not described in detail herein.

The preparation method of the ferroelectric memory is not particularly limited in the present invention, and the hybrid extrinsic ferroelectric Ca is prepared by a method well known in the art₃Ti₂O₇And doping compound thereof is used as negative piezoelectric material for preparing ferroelectric memory. FIG. 1 is a schematic diagram showing the displacement change of a positive piezoelectric material and a negative piezoelectric material under an electric field, wherein (a) shows the negative piezoelectric material, and (b) shows the positive piezoelectric material, when the polarization direction of the material is consistent with the direction of an external electric field, the material with positive piezoelectric property will elongate along the direction of the external electric field after the external electric field is applied, and the material with negative piezoelectric property will elongate along the direction of the external electric field after the external electric field is appliedThe electric field will contract in length along the direction of the external electric field.

The invention provides a hybrid extrinsic ferroelectric Ca₃Ti₂O₇And the application of the doped compound in the preparation of sensors. In the present invention, the sensor preferably comprises a piezoelectric sensor. The invention relates to the hybrid extrinsic ferroelectric Ca₃Ti₂O₇And the application of the doped compound thereof in the preparation of the sensor are not particularly limited, and the method well known in the art can be selected.

The invention provides a hybrid extrinsic ferroelectric Ca₃Ti₂O₇And the use of doped compounds thereof for the production of brakes. In the present invention, the actuator preferably comprises a piezoelectric displacement actuator or a micro-ceramic actuator. The invention relates to the hybrid extrinsic ferroelectric Ca₃Ti₂O₇The method of application of the doped compound thereof in the field of brake is not particularly limited, and a method known in the art may be selected.

The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. It is to be understood that the described embodiments are merely exemplary of the invention, and not restrictive of the full scope of the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.