SrTiO3-based ceramic with ultrahigh dielectric constant and low dielectric loss and preparation method thereof

Abstract

The application discloses a SrTiO3-based ceramic with ultrahigh dielectric constant and low dielectric loss, and a chemical composition of the ceramic is Sr 1‑1.5x Gd x TiO3 (0.008≤ x ≤0.014). A preparation method comprises the following steps: according to a stoichiometric formula Sr 1‑1.5x Gd x TiO3, primary ball milling, drying, grinding, briquetting, pre-sintering, obtaining a block B, secondary ball milling, drying, grinding, sieving, pressing a green body, and sintering. 1‑1.5x Gd x The SrTiO3-based ceramic material has ultrahigh dielectric constant ε r (>10 5 ) and low dielectric loss tanδ (<0.05), the preparation process is simple, the material cost is low, the sintering is carried out in a nitrogen environment, the process is safe, and the process is green and environment-friendly.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of medium ceramics, in particular to a SrTiO3-based ceramic with ultrahigh dielectric constant and low dielectric loss and a preparation method thereof. BACKGROUND

[0002] With the increasing demand for miniaturization of electronic devices in modern electronic industry, there is an urgent need to develop materials with excellent stability in a wider frequency and temperature range, giant dielectric constant and low dielectric loss. The current mainstream giant dielectric matrix materials BaTiO3, CaCu3Ti4O 12 , NiO, TiO2, SrTiO3 (referred to as ST) and the like can basically make the dielectric constant ε r > 10 4 after modification. However, these materials are accompanied by higher dielectric loss tanδ> 0.05 and poor frequency and temperature stability.

[0003] The ST material in the above mainstream giant dielectric matrix materials has a band gap of 3.2 eV, a high room temperature dielectric constant ε r (about 300), and excellent basic properties such as high breakdown field strength (> 200 kV / cm), high insulation resistance and low dielectric loss (tanδ< 0.01); at the same time, compared with CaCu3Ti4O 12 , BaTiO3, NiO and other matrix materials, ST has good temperature / frequency stability, so ST is the best candidate material system for giant dielectric low-loss materials. However, to further increase the dielectric constant ε r of ST-based ceramic materials to close to or exceed 10 5of the order of magnitude of 10, usually need to be sintered in an atmosphere of hydrogen and its mixed gas

X. Zhang, Y. P. Pu, L. Zhang, J. B. Zhang, Y. T. Ning, Y. C. Shang, X. Lu, X. Q. Zhang, Simultaneously achieving colossal permittivity, ultralow dielectric loss tangent, and high insulation resistivity in Er-doped SrTiO3 ceramics via oxygen vacancy regulation, ACS Appl. Mater. Interfaces 14 (2022) 48821-4883; R. Gu, X. Guo, J. R. Kang, R. P. Ma, H. L. Hao, H. C. Sun, Y. Lan, Z. Xu, L. Jin, X. Y. Wei, Colossal permittivity and ultralow dielectric loss in SrTi 1-x Nb x O3ceramics sintered at different atmospheres via defect chemistry improvement, Ceramics International 48 (9) (2022) 12692-12698

[0004] The purpose of the present application is to study a ceramic material with ultra-high giant dielectric constant (ε r > 10 5 ) and low dielectric loss (tanδ < 0.05) under non-hydrogen sintering conditions, so as to solve the problems of complex preparation process, high material cost, unsafe sintering process and increased dielectric loss when preparing the existing technology of ultra-high giant dielectric constant ST ceramic material.

[0005] In order to achieve the above purpose, the technical scheme adopted by the present application is as follows:

[0006] An ultra-high dielectric constant and low dielectric loss SrTiO3-based ceramic, the chemical composition of which is Sr 1-1.5x Gd x TiO3, wherein, 0.008 ≤x ≤0.014, x as a percentage of molar mass.

[0007] The preparation method of the ultra-high dielectric constant and low dielectric loss SrTiO3-based ceramic comprises the following steps:

[0008] Step 1, SrCO3, TiO2 and Gd2O3 raw powder are weighed according to the stoichiometric formula Sr 1-1.5x Gd x TiO3 composition;

[0009] Step 2, the mixed raw powder is ball milled once; the slurry after ball milling is dried to obtain mixture A;

[0010] Step 3, mixture A is ground and briquetted, and then pre-fired in air to obtain pre-fired briquette B;

[0011] Step 4, the briquette B is crushed and ball milled again; the slurry after ball milling is dried, ground and sieved to obtain mixture C;

[0012] Step 5, mixture C is pressed into a green body;

[0013] Step 6, the pressed green body is sintered to obtain Sr 1-1.5x Gd x TiO3-based ceramic.

[0014] Further, the SrCO3, TiO2 and Gd2O3 raw powder in step 1 is chemically pure.

[0015] Further, in step 2, the mass ratio of raw powder: zirconia ball stone: deionized water during the first ball milling is 1:5:(0.8-1.2), the ball milling speed is 300 r / min, and the ball milling time is 6 h; the slurry after ball milling is dried at a temperature of 80-100℃ for 16-24 h.

[0016] Further, in step 3, the pre-firing temperature is 1140-1160℃, and the time is 3 h.

[0017] Further, in step 4, the mass ratio of briquette B: zirconia ball stone: deionized water during the second ball milling is 1:(4-5):(0.8-1.2), the ball milling speed is 300 r / min, and the ball milling time is 6 h; the slurry after ball milling is dried at a temperature of 80-100℃ for 16-24 h.

[0018] Further, in step 4, a 120-mesh sieve is used for sieving.

[0019] Further, in step 5, isostatic pressing is adopted for pressing.

[0020] Preferably, the pressing adopts cold isostatic pressing.

[0021] Further, the step 6 sintering is carried out in a nitrogen environment, and the sintering temperature is 1500-1550℃, and the temperature is kept for 2-4h.

[0022] Compared with the prior art, the present application has the following beneficial technical effects:

[0023] The Sr 1-1.5x Gd x TiO3-based ultra-high dielectric constant and low dielectric loss ceramic material has ultra-high dielectric constant ε r (>10 5 ) and low dielectric loss tan δ (<0.05); and the preparation process is simple, and the material cost is low; sintering in a nitrogen environment is safe, green and environmentally friendly; and the material can become an important candidate dielectric ceramic material in the high-end industrial application field in terms of technology and economy. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 is the XRD pattern of the conventional ST ceramic and the Sr 1-1.5x Gd x TiO3-based ceramic prepared in examples 1-4.

[0025] Figure 2 is the SEM photo of the conventional ST ceramic and the Sr 1-1.5x Gd x TiO3-based ceramic prepared in examples 1-4.

[0026] Figure 3 is the dielectric spectrum of the Sr 1-1.5x Gd x TiO3-based ceramic prepared in examples 1-4.

[0027] Figure 4 is the XPS pattern of the conventional ST ceramic and the Sr 1-1.5x Gd x TiO3-based ceramic prepared in example 2.

[0028] Figure 5 is the dielectric constant and dielectric loss comparison pattern of the Sr 1-1.5x Gd x TiO3-based ceramic prepared in examples 1, 2 and 3 and other giant dielectric materials under room temperature and 1kHz test conditions.

[0029] In the drawings, SGdT8, SGdT10, SGdT12 and SGdT14 respectively represent example 1 ( x =0.008), example 2 ( x =0.01), example 3 (x =0.012), Example 4 ( x Sr prepared with =0.014) 1-1.5x Gd x TiO3-based ceramics. Detailed Implementation

[0030] Various exemplary embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0031] The chemical formula of the SrTiO3-based ceramic designed in this invention is Sr 1-1.5x Gd x TiO3 (where 0.008≤ x ≤0.014), by introducing Gd 3+ Forming defective dipoles , , These three defect dipoles promote the generation of ultra-high dielectric constant, while the internal barrier layer capacitance (IBLC) effect also plays an important role in improving dielectric properties, thus enabling the ceramic of the present invention to have both ultra-high dielectric constant and low dielectric loss.

[0032] The method for preparing SrTiO3-based ceramics with ultra-high dielectric constant and low dielectric loss of the present invention includes the following steps:

[0033] Step 1: Mix chemically pure SrCO3, TiO2, and Gd2O3 raw powders according to the stoichiometric formula Sr 1-1.5x Gd x TiO3 (where 0.008≤ x ≤0.014, x Weigh and dispense ingredients according to their composition (in molar mass percentages);

[0034] Step 2: Mix the prepared raw powder and add it to a ball mill jar for one ball milling. The mass ratio of raw powder, zirconia balls, and deionized water is 1:5:(0.8~1.2). The ball milling speed is 300 r / min and the ball milling time is 6 h. The slurry after ball milling is dried at 80~100℃ for 16~24 h to obtain mixture A.

[0035] Step 3: Grind and press mixture A into blocks, then pre-fire it in air at a temperature of 1140~1160℃ for 3 hours to obtain pre-fired block material B.

[0036] Step 4, the block B is crushed and then added into the ball mill tank for secondary ball milling, the mass ratio of block B: zirconia ball stone: deionized water is 1:(4-5):(0.8-1.2), the ball milling speed is 300 r / min, and the ball milling time is 6 h; the slurry after ball milling is dried at 80-100 ℃ for 16-24 h, ground and sieved through a 120 mesh screen to obtain mixture C for standby;

[0037] Step 5, the mixture C is pressed into a green body. In the present application, the isostatic pressing mode is selected, and the isostatic pressing mode is used to press at 200 MPa for 4 min, then press at 190 MPa for 4 min and then unload, in order to save energy, the cold isostatic pressing is preferred;

[0038] Step 6, the pressed green body is placed in a sagger, the sagger is placed in a tube furnace, and sintering is carried out at 1500-1550 ℃ in a nitrogen atmosphere for 2-4 h to obtain Sr 1-1.5x Gd x TiO3-based ceramic. The sagger is preferably an alumina sagger, and a zirconia pad is laid at the bottom of the sagger.

[0039] The above-mentioned raw materials are all purchased from the market.

[0040] The technical solutions of the present application are further described below through specific examples.

[0041] Example 1

[0042] x =0.008.

[0043] In the primary ball milling, the mass ratio of raw powder: zirconia ball stone: deionized water is 1:5:0.8; the slurry after ball milling is dried at 90 ℃ for 20 h to obtain mixture A;

[0044] In the pre-sintering, the sintering temperature is 1150 ℃ to obtain pre-sintered block B;

[0045] In the secondary ball milling, the mass ratio of block B: zirconia ball stone: deionized water is 1:4:1; the slurry after ball milling is dried at 100 ℃ for 18 h, and then ground and sieved to obtain mixture C;

[0046] In the sintering, the sintering temperature is 1500 ℃, and the holding time is 4 h to obtain Sr 1-1.5x Gd x TiO3-based ceramic.

[0047] Example 2

[0048] x =0.01.

[0049] The primary ball milling is carried out with the mass ratio of raw powder: zirconia ball: deionized water being 1:5:1.2, and the slurry after ball milling is dried at 100°C for 18h to obtain mixture A;

[0050] The pre-sintering is carried out at a sintering temperature of 1160°C to obtain pre-sintered block B;

[0051] The secondary ball milling is carried out with the mass ratio of block B: zirconia ball: deionized water being 1:4:0.8, and the slurry after ball milling is dried at 80°C for 24h to obtain mixture C after grinding and sieving;

[0052] The sintering is carried out at a sintering temperature of 1550°C for 2h to obtain Sr 1-1.5x Gd x TiO3-based ceramic.

[0053] Example 3

[0054] x =0.012.

[0055] The primary ball milling is carried out with the mass ratio of raw powder: zirconia ball: deionized water being 1:5:1.0, and the slurry after ball milling is dried at 80°C for 24h to obtain mixture A;

[0056] The pre-sintering is carried out at a sintering temperature of 1140°C to obtain pre-sintered block B;

[0057] The secondary ball milling is carried out with the mass ratio of block B: zirconia ball: deionized water being 1:5:1.2, and the slurry after ball milling is dried at 95°C for 16h to obtain mixture C after grinding and sieving;

[0058] The sintering is carried out at a sintering temperature of 1520°C for 3h to obtain Sr 1-1.5x Gd x TiO3-based ceramic.

[0059] Example 4

[0060] x =0.014.

[0061] The primary ball milling is carried out with the mass ratio of raw powder: zirconia ball: deionized water being 1:5:0.9, and the slurry after ball milling is dried at 95°C for 16h to obtain mixture A;

[0062] The pre-sintering is carried out at a sintering temperature of 1150°C to obtain pre-sintered block B;

[0063] The secondary ball milling is carried out with the mass ratio of block B: zirconia ball: deionized water being 1:4.5:1, and the slurry after ball milling is dried at 90°C for 20h to obtain mixture C after grinding and sieving;

[0064] sintering temperature is 1530℃, and the holding time is 2.5h, to obtain Sr 1-1.5x Gd x TiO3-based ceramic.

[0065] The ST ceramic samples prepared by the conventional process and the samples prepared in the above Examples 1-4 are polished and cleaned, silver electrode paste is coated on the ceramic surface, the ceramic material coated with silver electrode is sintered at a temperature of 750℃ for 25min for heat treatment, to obtain a dielectric ceramic device for dielectric property test.

[0066] The ST ceramic samples prepared by the conventional process and the samples prepared in the above Examples 1-4 are subjected to XRD test and comparison, to obtain Figure 1 Results. From Figure 1 it can be seen that all samples show cubic perovskite crystal structure, and no second phase is found. From Figure 1 the insert, it can be seen that the (110) diffraction peak shifts to high angle, indicating that Gd 3+ (125pm) enters the Sr 2+ (144pm) site, forming point defects .

[0067] SEM photos of the ST ceramic samples prepared by the conventional process and the samples prepared in the above Examples 1-4 are taken, to obtain Figure 2 Results. According to microscopic test, the average particle sizes of the ST ceramic samples prepared by the conventional process and the samples prepared in the above Examples 1-4 are: the conventional ST ceramic sample 12.06μm, the SGdT8 ceramic sample 21.13μm, the SGdT10 ceramic sample 74.45μm, the SGdT12 ceramic sample 48.26μm, and the SGdT14 ceramic sample 19.31μm. From Figure 2 it can be seen that all Gd 3+ doped samples obtain dense ceramic structure. With the introduction of Gd 3+ doping, the average grain size of the ceramic shows a trend of first increasing and then decreasing, and the average grain size of the SGdT10 sample reaches the maximum value.

[0068] The dielectric properties of the ceramic samples prepared in the above Examples 1-4 are tested, to obtain Figure 3 Results. Figure 3 is the dielectric spectrum of the Sr 1-1.5x Gd x TiO3 ceramic material in Examples 1-4, from Figure 3 it can be seen that in the test frequency range of 20Hz-2MHz, the dielectric constants ε r of the SGdT8, SGdT10 and SGdT12 samples all remain above 10 5 , and the dielectric constant ε r of the SGdT14 sample also remains above 105 All the samples in the examples have a dielectric loss tan δ lower than 0.1 in the frequency range from 20 Hz to 1 MHz. The SGdT10 sample has particularly outstanding node performance, almost maintaining a dielectric constant ε r higher than 2 x 10 5 in the entire test frequency range, and a dielectric loss tan δ lower than 0.05. It can be seen that the dielectric constant ε r is directly proportional to the average grain size of the ceramic sample, which indicates that the internal barrier layer capacitance (IBLC) effect plays an important role in the increase of the dielectric constant ε r .

[0069] The ST ceramic sample and the sample in Example 2 were subjected to XPS testing and comparison, and the results are shown in Figure 4 . Figure 4 The XPS spectra of the samples in Example 2 and the ST ceramic sample are shown in FIG. 6. As can be seen from the O 1s fine spectrum, the fitting peak with a binding energy of 529.4 eV corresponds to the Ti-O bond, and the fitting peak with a binding energy of 531.5-531.6 eV is attributed to the adsorbed H2O on the surface. The O 1s fitting peak related to oxygen vacancies is only observed in the SGdT10 ceramic, with a binding energy of 530.5 eV. In the Ti 2p fine spectrum, the Ti 2p 3 / 2 peak with a binding energy of 458.2-458.3 eV and the Ti 2p 1 / 2 peak with a binding energy of 464.0 eV are related to Ti 4+ ions. Meanwhile, the Ti 2p 3+ and Ti 2p 3 / 2 fitting peaks corresponding to Ti 1 / 2 ions are also detected in the Ti 2p spectrum, with binding energies of 458.7-457.8 eV and 462.4 eV, respectively. After Gd 3+ doping, the concentration ratio of Ti 3+ / Ti 4+ increases from 17.92% to 18.83%. The above results show that the SGdT10 ceramic sample has more oxygen vacancies and Ti 3+ ions, and Ti 3+ is associated with oxygen vacancies to form defect dipoles . With the increase of the Gd doping amount, more are generated in the SGdT ceramic, more oxygen vacancies are generated to compensate the charge of , and more Ti is associated with oxygen vacancies, to form defect dipoles , , , which promote the generation of the ultra-high dielectric constant.

[0070] As Figure 5 shown, the dielectric constant ε r and dielectric loss tanδ of the ceramic samples of examples 1, 2 and 3 and other giant dielectric materials were tested and compared at room temperature and 1 kHz. The test results show that the other giant dielectric materials either have a low dielectric constant ε r or a high dielectric loss tanδ, and cannot achieve both a high dielectric constant ε r and a low dielectric loss tanδ; while the dielectric constant ε r of the SGdT8 ceramic sample of the present application is 145396, and the dielectric loss tanδ is 0.003; the dielectric constant ε r of the SGdT10 ceramic sample is 217249, and the dielectric loss tanδ is 0.025; the dielectric constant ε r of the SGdT12 ceramic sample is 169854, and the dielectric loss tanδ is 0.020; the ceramic samples prepared in examples 1, 2 and 3 simultaneously have an ultrahigh dielectric constant ε r (>10 5 ) and a low dielectric loss tanδ (<0.05).

[0071] The Sr 1-1.5x Gd x TiO3-based ceramic material prepared by the method of the present application simultaneously has an ultrahigh dielectric constant ε r (>10 5 ) and a low dielectric loss tanδ (<0.05), and can be widely used in the field of high-dielectric energy storage; only three raw materials are used in the formula, so the preparation process is simple and the material cost is low; in addition, the ceramic material of the present application is sintered in a nitrogen environment, so the process is safe and green.

[0072] The above merely provides the preferred specific embodiments of the present application, but the protection scope of the present application is not limited thereto, and any changes or substitutions within the technical scope disclosed by the present application can be easily thought of by those skilled in the art, and should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. An ultra-high dielectric constant and low dielectric loss SrTi03-based ceramic, characterized by, The chemical composition of Sr 1- 1.5x Gd x TiO3, wherein 0.008≤ x ≤0.014, x is a molar mass percentage; the ceramic is obtained by sintering in a nitrogen atmosphere, the sintering temperature is 1500~1550℃, and the holding time is 2~4h; and the dielectric constant ε r >1×10 5 , the dielectric loss tanδ<0.

05.

2. The method of claim 1, wherein the method is characterized by: The method comprises the following steps: Step 1, SrCO3, TiO2and Gd2O3raw powders were weighed according to the stoichiometric formula Sr 1-1.5x Gd x TiO3composition; Step 2: mixing the prepared raw powder and carrying out primary ball milling; drying the slurry after ball milling to obtain mixture A; Step 3: grinding and briquetting mixture A and pre-sintering in air to obtain pre-sintered briquettes B; Step 4: crushing briquettes B and carrying out secondary ball milling; drying, grinding and sieving the slurry after ball milling to obtain mixture C; Step 5: pressing mixture C into a green body; Step 6: sintering the pressed green body to obtain Sr 1-1.5x Gd x TiO3-based ceramic.

3. The method of claim 2, wherein the method is characterized by: The SrCO3, TiO2 and Gd2O3 raw powder in step 1 is chemically pure.

4. The method of claim 2, wherein the method is characterized by: In step 2, the mass ratio of raw powder: zirconia ball stone: deionized water is 1:5:(0.8-1.2) during primary ball milling, the ball milling speed is 300 r / min, the ball milling time is 6 h; the slurry after ball milling is dried at 80-100 ℃ for 16-24 h.

5. The method of producing SrTi03-based ceramics with ultra-high dielectric constant and low dielectric loss according to claim 2, characterized in that, The pre-sintering temperature in step 3 is 1140-1160 ℃, and the time is 3 h.

6. The method of producing SrTi03-based ceramics with ultra-high dielectric constant and low dielectric loss according to claim 2, characterized in that, In step 4, the mass ratio of briquettes B: zirconia ball stone: deionized water is 1:(4-5):(0.8-1.2) during secondary ball milling, the ball milling speed is 300 r / min, the ball milling time is 6 h; the slurry after ball milling is dried at 80-100 ℃ for 16-24 h.

7. The method of producing super high dielectric constant and low dielectric loss SrTi03-based ceramics according to claim 2, characterized by, The sieving in step 4 uses a 120-mesh sieve.

8. The method of producing SrTi03-based ceramics with ultra-high dielectric constant and low dielectric loss according to claim 2, characterized in that, The pressing in step 5 adopts the cold isostatic pressing mode.

9. The method of claim 8, wherein the method is characterized by: The pressing adopts the cold isostatic pressing mode.

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