Hybrid ferroelectric ceramic material with layered perovskite structure and method for its production

Abstract

The application discloses a hybrid unconventional ferroelectric ceramic material with a layered perovskite structure and a preparation method thereof. 1+x Ln 2‑x Sc2O7, Ln=Nd, Sm, Eu, one or more of them, 0.0 1.05 Nd 1.95 Sc2O7, Sr 1.1 Sm 1.9 Sc2O7, Sr 1.15 Eu 1.85 Sc2O7. The preparation method comprises the following steps: (a) according to the chemical formula Sr 1.05 Nd 1.95 Sc2O7, Sr 1.1 Sm 1.9 Sc2O7, Sr 1.15 Eu 1.85 Sc2O7, raw materials SrCO3, Nd2O3, Sm2O3, Eu2O3 and Sc2O3 are weighed, ball-milled, dried, sieved, and then calcined; (b) the powder prepared in the step (a) is sieved after secondary ball-milling; (c) the powder prepared in the step (b) is added with a binder, pressed into a tablet, sintered after plastic arrangement, and thus the ceramic material is prepared. Under the test conditions of room temperature, a test frequency of 2 Hz and a highest applied electric field of 400 kV / cm, the measured residual ferroelectric polarization value of the Sr 1.05 Nd 1.95 Sc2O7 ceramic is 0.9-1.1 muC / cm 2 , Sr 1.1 Sm 1.9 Sc2O7 ceramic is 2-3 muC / cm 2 , Sr 1.15 Eu 1.85 Sc2O7 ceramic is 0.5-0.75 muC / cm 2 .

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of functional ceramic materials, and relates to a ferroelectric ceramic material and a preparation method thereof, in particular to a hybrid unconventional ferroelectric ceramic material with a layered perovskite structure and a preparation method thereof. BACKGROUND

[0002] The information age is driving electronic components to be miniaturized, lightened and integrated, and information storage components urgently need to improve storage speed, storage density and reduce storage energy consumption. Scientists have tried to develop various storage medium materials. Ferroelectric materials have become the focus of research in the field of modern information storage technology due to their unique physical properties, such as the reversible reversal of the polarization direction under the action of an external electric field. These characteristics make ferroelectric materials show great potential in the development of high-density, non-volatile memories.

[0003] At present, there are many reports on conventional ferroelectric materials. The spontaneous polarization of conventional ferroelectric materials originates from the second-order Jahn-Teller effect, but cations with empty d orbitals or lone pair electrons are a prerequisite for the second-order Jahn-Teller effect, which will greatly limit the types of ferroelectric oxides. Therefore, in order to further enrich the types of ferroelectric materials, hybrid unconventional ferroelectric materials have attracted great interest from researchers. Based on the simple perovskite structure, a series of layered perovskite structure materials can be derived. In recent years, researchers have found that this type of material has a new type of hybrid unconventional ferroelectricity. Hybrid unconventional ferroelectricity originates from the second-order ferroelectric sequence induced by non-polar modules such as oxygen octahedral distortion, and does not require the second-order Jahn-Teller effect active ion required by conventional ferroelectricity. Exploring ferroelectricity in materials with layered perovskite structure has important scientific and practical significance for widening the research scope of hybrid unconventional ferroelectricity and deepening the understanding of its mechanism. SUMMARY

[0004] The reported hybrid unconventional ferroelectric ceramic material system with a layered perovskite structure needs to be further developed. Based on this, the purpose of the present application is to provide a hybrid unconventional ferroelectric ceramic material with a layered perovskite structure and a preparation method thereof. Based on component design, by adjusting the stoichiometric ratio, the generation of the second phase is avoided, and a completely single target component ferroelectric ceramic material is obtained.

[0005] In the first aspect, the application provides a hybrid unconventional ferroelectric ceramic material with a layered perovskite structure, the chemical formula of the ceramic is Sr 1+x Ln 2-x Sc2O7 (Ln = Nd, Sm, Eu; 0.0 < x < 0.2), preferably Sr 1.05 Nd 1.95 Sc2O7, Sr 1.1 Sm1.9 Sc2O7, Sr 1.15 Eu 1.85 Sc2O7.

[0006] In a second aspect, the present application provides a preparation method of a hybrid unconventional ferroelectric ceramic material with layered perovskite structure, which comprises the following steps:

[0007] (1) Raw materials SrCO3, Nd2O3, Sm2O3, Eu2O3 and Sc2O3 are weighed according to the chemical formula Sr 1.05 Nd 1.95 Sc2O7, Sr 1.1 Sm 1.9 Sc2O7 or Sr 1.15 Eu 1.85 Sc2O7 are weighed, and after ball milling, they are dried and sieved.

[0008] (2) The powder prepared in step (1) is calcined, and after secondary ball milling, it is dried, ground, granulated, and sieved to obtain a powder with uniform particles.

[0009] (3) The powder prepared in step (2) is added with a binder to press into a cylindrical green body, and after plastic removal, it is sintered to obtain the hybrid unconventional ferroelectric ceramic material with layered perovskite structure.

[0010] Further, in steps (1) and (2), the ball milling method is wet ball milling, anhydrous ethanol is used as the ball milling medium, and the mass ratio of the material, the grinding ball and the anhydrous ethanol is 1:2:(0.5-1.5) during ball milling, the ball milling time is 12-36 hours, and preferably 24 hours.

[0011] Further, in step (2), the calcination temperature is 900-1000°C, and the time is 3-9 hours, and preferably 1000°C for 6 hours.

[0012] Further, in step (3), the binder is a polyvinyl alcohol (PVA) aqueous solution with a concentration of 8wt%, and the addition amount is 5-15% of the mass of the ceramic powder, and preferably 8-12%, the plastic removal temperature is 500-800°C for 1-3 hours, and preferably 600°C for 2-3 hours.

[0013] Further, in step (3), the sintering is to bury the green body in a crucible filled with powder with the same composition as the green body, the sintering temperature is 1450°C-1550°C, the holding time is 3-12 hours, and the heating rate is 5-10°C / min.

[0014] The hybrid unconventional ferroelectric ceramic material with a layered perovskite structure obtained by the preparation method of this invention exhibits excellent ferroelectric properties. A complete hysteresis loop can be measured at room temperature. Under test conditions of 2 Hz and a maximum applied electric field of 400 kV / cm, Sr... 1.1 Sm 1.9 The remanent polarization value measured for Sc2O7 ceramics is 2–3 μC / cm. 2 Sr 1.05 Nd 1.95 The remanent polarization of Sc2O7 ceramics was measured to be 0.9–1.1 μC / cm. 2 Sr 1.15 Eu 1.85 The remanent polarization value measured for Sc2O7 ceramics is 0.5~

[0015] 0.75μC / cm 2 This invention can obtain ferroelectric ceramic materials with no second phase and completely single target composition, further enriching the types of hybrid unconventional ferroelectric materials; the preparation process of this invention is simple and has good reproducibility. Attached Figure Description

[0016] Figure 1a , Figure 1b , Figure 1c The X-ray diffraction patterns of the ceramic samples in Examples 1-3 are shown in the Rietveld fitting results.

[0017] Figure 2 These are surface microstructure images of Examples 1-3;

[0018] Figure 3a , Figure 3b , Figure 3c The figures show typical hysteresis loops of the ceramic samples from Examples 1-3, measured at room temperature. Detailed Implementation

[0019] To enable those skilled in the art to better understand the present invention, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. The specific process parameters in the examples below are merely examples within a suitable range. That is, those skilled in the art can make appropriate selections within the appropriate range based on the description herein, and are not intended to limit themselves to the specific values ​​in the examples below. It should be understood that the following embodiments are only for illustrating the present invention, and not for limiting the present invention.

[0020] Example 1: The chemical composition of the ferroelectric ceramic is: Sr 1.1 Sm 1.9 Sc2O7

[0021] (1) SrCO3(99.95%), Sm2O3(99.99%), Sc2O3(99.99%) powders were used as raw materials, and the raw materials were mixed and weighed according to the corresponding stoichiometric ratio.

[0022] (2) The weighed raw materials were put into a ball mill tank, the ball mill medium was anhydrous ethanol, and the mixture was ball milled for 24 hours according to the mass ratio of raw material, zirconium ball and anhydrous ethanol of 1:2:1. After ball milling, drying, and passing through a 120 mesh screen were carried out in sequence.

[0023] (3) The sieved powder was poured into a crucible and pre-sintered at 1000°C in air for 6 hours to obtain the desired target product. Then the calcined powder was mixed according to the mass ratio of raw material, zirconium ball and anhydrous ethanol of 1:2:1, and then ball milled for 24 hours, dried and ground to pass through a 120 mesh screen.

[0024] (4) 8wt% PVA was added as a binder to the obtained mixed powder to form granules, the amount added was 10% of the mass of the ceramic powder, and after granulation, the powder was sieved through 40 and 80 meshes to obtain a uniform granular powder. The cylindrical green body with a diameter of 12 mm and a thickness of about 1.5 mm was pressed under a pressure of 100 MPa, and then plasticized at 600°C for 2 hours to obtain a sintered body.

[0025] (5) The sintered body was buried in a crucible containing the same powder as the body composition, and heated to 1550°C at a rate of 5°C / min, held for 6 hours, then cooled to 1100°C at a rate of 2°C / min, and then cooled to room temperature with the furnace, and then taken out to obtain the desired dense layered perovskite-like hybrid unconventional ferroelectric ceramic material.

[0026] The ceramic sample prepared in Example 1 was subjected to X-ray diffraction analysis test, and the results are shown in Figure Figure 1a . As can be seen from the figure, the ceramic sample of Example 1 has no impurity phase.

[0027] The sintered surface of the ceramic sample prepared in Example 1 was subjected to scanning electron microscope analysis, and the surface morphology diagram obtained is shown in Figure Figure 2 . As can be seen from the figure, the ceramic surface is dense.

[0028] The surface of the ceramic sample prepared in Example 1 was ground, thinned, and gold sprayed, and then subjected to ferroelectric performance test with a ferroelectric tester, the test frequency was 2 Hz, and the highest electric field applied was 400 kV / cm. The typical electric hysteresis loop measured at room temperature is shown in Figure Figure 3a .

[0029] Example 2: The chemical composition of the ferroelectric ceramic is: Sr 1.05 Nd 1.95 Sc2O7

[0030] SrCO3(99.95%), Nd2O3(99.99%), Sc2O3(99.99%) powders as raw materials, the raw material powders are mixed and weighed according to the corresponding stoichiometric ratio. Then the preparation method of Example 1 is repeated according to the above formula.

[0031] The ceramic sample prepared in this Example 2 is subjected to X-ray diffraction analysis test, and the results are shown in the attached Figure 1b From the figure, it can be seen that the ceramic of Example 2 obtained has no impurity phase.

[0032] The sintered surface of the ceramic sample prepared in this Example 2 is subjected to scanning electron microscope analysis, and the surface morphology diagram obtained is shown in the attached Figure 2 From the figure, it can be seen that the ceramic surface is dense.

[0033] After the surface of the ceramic sample prepared in this Example 2 is ground, thinned and gold sprayed, the ferroelectric performance test is carried out by using a ferroelectric tester, the test frequency is 2 Hz, the highest electric field applied is 400 kV / cm, and the typical electric hysteresis loop measured at room temperature is shown in the attached Figure 3b .

[0034] Example 3: The chemical composition of the ferroelectric ceramic is: Sr 1.15 Eu 1.85 Sc2O7

[0035] SrCO3(99.95%), Eu2O3(99.99%), Sc2O3(99.99%) powders as raw materials, the raw material powders are mixed and weighed according to the corresponding stoichiometric ratio. Then the preparation method of Example 1 is repeated according to the above formula.

[0036] The ceramic sample prepared in this Example 3 is subjected to X-ray diffraction analysis test, and the results are shown in the attached Figure 1c From the figure, it can be seen that the ceramic of Example 3 obtained has no impurity phase.

[0037] The sintered surface of the ceramic sample prepared in this Example 3 is subjected to scanning electron microscope analysis, and the surface morphology diagram obtained is shown in the attached Figure 2 From the figure, it can be seen that the ceramic surface is dense.

[0038] After the surface of the ceramic sample prepared in this Example 3 is ground, thinned and gold sprayed, the ferroelectric performance test is carried out by using a ferroelectric tester, the test frequency is 2 Hz, the highest electric field applied is 400 kV / cm, and the typical electric hysteresis loop measured at room temperature is shown in the attached Figure 3c .

[0039] The above content only illustrates the technical idea of the present application, and cannot limit the protection scope of the present application. Any modification made according to the technical idea of the present application on the basis of the technical solution falls within the protection scope of the claims of the present application.

Claims

1. A hybrid non-conventional ferroelectric ceramic material having a layered perovskite structure, characterized in that, The chemical formula of the ceramic material is Sr 1+x Ln 2-x Sc2O7, wherein Ln is one or more of Sm, Nd, Eu, and 0 < x < 0.

2.

2. The hybrid non-ferroelectric ceramic material with layered perovskite structure according to claim 1, characterized in that The ceramic material is preferably a strontium scandium neodymium based ferroelectric ceramic material Sr 1.05 Nd 1.95 Sc2O7, a strontium scandium samarium based ferroelectric ceramic material Sr 1.1 Sm 1.9 Sc2O7, a strontium scandium europium based ferroelectric ceramic material Sr 1.15 Eu 1.85 Sc2O7.

3. The hybrid non-ferroelectric ceramic material with layered perovskite structure according to claim 1, characterized in that Sr 1.05 Nd 1.95 The measured remnant ferroelectric polarization of the Sc2O7ceramics is 0.9-1.1 μC / cm 2 , Sr 1.1 Sm 1.9 The measured remnant ferroelectric polarization of the Sc2O7ceramics is 2-3 μC / cm 2 , Sr 1.15 Eu 1.85 The measured remnant ferroelectric polarization of the Sc2O7ceramics is 0.5-0.75 μC / cm 2 .

4. A method for producing a hybrid ferroelectric ceramic material having a layered perovskite structure according to claim 2, characterized by, The method comprises the following steps: (1) The raw materials SrCO3, Nd2O3, Sm2O3, Eu2O3 and Sc2O3 are respectively weighed according to the chemical formula Sr 1.05 Nd 1.95 Sc2O7, Sr 1.1 Sm 1.9 Sc2O7, Sr 1.15 Eu 1.85 Sc2O7 are dosed, dried and sieved after ball milling; (2) calcining the powder prepared in step (1), secondary ball milling, drying and sieving; (3) adding the powder prepared in step (2) into a binder, tabletting, plastic removal, sintering to obtain the ceramic material.

5. The preparation method according to claim 4, characterized in that, In step (1), the ball milling method is wet ball milling, anhydrous ethanol is used as the ball milling medium, the mass ratio of the material, the grinding ball and the anhydrous ethanol is 1:2:(0.5-1.5), and the ball milling time is 12-36 hours.

6. The preparation method according to claim 4, characterized in that, In step (2), the calcining temperature is 900-1100℃, and the time is 3-9 hours.

7. The preparation method according to claim 4, characterized in that, In step (3), the binder is a polyvinyl alcohol aqueous solution with a concentration of 8wt%, the adding amount is 5-15% of the mass of the ceramic powder, the plastic removal temperature is 500-800℃, and the time is 1-3 hours.

8. The preparation method according to claim 4, characterized in that, In step (3), the sintering temperature is 1450-1550℃, the time is 3-12 hours, and the heating rate is 5-10℃ / min.

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