A double-doped strontium titanate-based giant dielectric ceramic material at sites A and B and a preparation method thereof

Abstract

The present invention relates to the technical field of electronic functional materials, and provides a strontium titanate-based giant dielectric ceramic material with dual donors co-doped at the A and B sites and a preparation method thereof. The present invention adopts a method of co-doping Sm at the Sr(A) site and Nb at the Ti(B) site, and combines nitrogen sintering to obtain a Sr(A)-based giant dielectric ceramic material with a chemical formula of Sr(B). 1‑ 1.5x Sm x Ti 0.097 Nb 0.003 The invention discloses a SrTiO3-based giant dielectric ceramic material with a dielectric constant of 0.018 (0<x≤0.018), which has a giant dielectric effect and good temperature stability of the dielectric constant, meeting the demand for dielectric materials for miniaturization of electronic components. In addition, the amount of dopants Nb2O5 and Sm2O3 used in the invention is relatively small, which can reduce production costs. At the same time, the preparation method provided by the invention has simple steps, good repeatability, high yield, low cost, and is convenient for commercial production.

Description

Technical Field

[0001] The present invention relates to the technical field of electronic functional materials, and in particular to a strontium titanate-based giant dielectric ceramic material co-doped with double donors at A and B positions and a preparation method thereof. Background Art

[0002] Giant dielectric ceramic materials have attracted widespread attention due to their applications in device miniaturization. In the past few years, a large number of studies on giant dielectric ceramic materials have been reported. For example, although ferroelectric BaTiO3-based ceramics have a high dielectric constant, their crystal structure changes with increasing temperature (from cubic phase to tetragonal phase at ~120℃), which causes the dielectric constant to increase sharply to ε r ~10 4 , affecting its application at high temperature. NiO and CaCu3Ti4O 12 (CCTO) based ceramics due to its huge dielectric constant (ε r >10 4 ), weak frequency and temperature dependence has attracted people's attention, but the high dielectric loss (tanδ>0.1) limits its application in devices. Although donor-acceptor co-doped TiO2-based ceramics can obtain excellent dielectric properties (ε r >10 4 , tanδ<0.05), but its low breakdown strength makes it difficult to apply. Therefore, it is very important to develop ceramic materials that meet the requirements of giant dielectric constant, low dielectric loss, high breakdown strength and dielectric properties, and remain stable over a wide temperature range.

[0003] SrTiO3 ceramics have an ABO3 perovskite structure and have attracted widespread attention due to their high breakdown strength (~200kV / cm), low dielectric loss (tanδ~0.005), and the ability to maintain the paraelectric phase over a wide temperature range. However, their low intrinsic dielectric constant makes them difficult to apply. Ion doping and sintering in a non-oxidizing atmosphere can effectively improve the dielectric constant of SrTiO3-based giant dielectric ceramics. For example, Wang et al. (ZJWang, MH Cao, ZHYao, Q. Zhang, Z. Song, W. Hu, Q. Xu, H. Hao, HX Liu, ZY Yu, Giant permittivity and low dielectric loss of SrTiO3 ceramics sintered in nitrogen atmosphere, J. Eur. Ceram. Soc. 34 (2014) 1755-1760.) used nitrogen atmosphere to sinter pure phase SrTiO3 and obtained excellent dielectric properties (ε r~47601, tan δ ~0.0058), the improvement of dielectric properties comes from the complete ionization of oxygen vacancies during high-temperature sintering in a nitrogen atmosphere, which improves the concentration of defects. Guo et al. (X. Guo, Y. P. Pu, W. Wang, L. Zhang, J. M. Ji, R. K. Shi, Y. Shi, M. D. Yang, and J. W. Li, High Insulation Resistivity and Ultralow Dielectric Loss in La-Doped SrTiO3Colossal Permittivity Ceramics through Defect Chemistry Optimization, ACS Sustainable Chem. Eng. 2019 (7) 13041-1305.) used La 3+ Sr(A) site donor-doped SrTiO3ceramics and sintered in a nitrogen atmosphere, resulting in a giant dielectric constant of ~26897 and a low dielectric loss of ~0.005, the giant dielectric constant is attributed to the defect clusters The local polarization enhancement caused by pinned free electrons, this pinning effect also limits the long-range displacement of free electrons and thus reduces the dielectric loss. Luo et al. (L. C. Luo, J. L. Li, M. W. Wang, S. Yang, J. Wu, X. Y. Gao, C. C. Li, W. Y. Du, L. Zhang, F. Li, High dielectric permittivity and ultralow dielectric loss in Nb-doped SrTiO3ceramics, Ceram. Inter. 48 (2022) 28438-28443.) prepared Nb 5+ doped SrTiO3ceramics with a dielectric constant of ~30000 and a dielectric loss of ~0.004, Nb 5+ Donor doping at the Ti(B) site helps to improve the defect concentration and thus improve the dielectric properties. In summary, donor doping at A site or B site can effectively improve the concentration of defects and thus affect the dielectric properties. However, single element doping has limited range of improvement and regulation of ceramic material dielectric properties, and it is difficult to meet the application requirements of giant dielectric ceramics (ε r >10 5 ). Currently, there are few reports on the use of double donor co-doping in SrTiO3-based giant dielectric ceramics, and the development of A, B site double donor co-doped SrTiO3-based giant dielectric ceramics is of great practical significance. SUMMARY

[0004] In view of this, the present invention provides a giant dielectric ceramic material based on strontium titanate with dual donors co-doped at the A and B sites, and a preparation method thereof. The giant dielectric ceramic material based on strontium titanate with dual donors co-doped at the A and B sites provided by the present invention can achieve a giant dielectric constant when sintered in a nitrogen atmosphere, and the dielectric constant has good temperature stability, meeting the requirements for dielectric materials for miniaturized electronic components and energy storage devices.

[0005] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0006] A method for preparing a SrTiO3-based giant dielectric ceramic material co-doped with dual donors at the A and B sites comprises the following steps:

[0007] (1) SrCO3, TiO2, Nb2O5 and Sm2O3 are ball-milled according to the ratio in formula I, and the obtained ball-milled material is dried and calcined to obtain a synthetic powder;

[0008] Sr 1-1.5x Sm x Ti 0.097 Nb 0.003 O3 formula I;

[0009] In formula I: the value range of x is 0<x≤0.018;

[0010] (2) ball-milling the synthetic powder for a second time, followed by sieving and drying to obtain a second ball-milled material;

[0011] (3) mixing the secondary ball mill material, the binder and water, and then performing aging, granulation and dry pressing in sequence to obtain a ceramic body;

[0012] (4) Debinding and sintering the ceramic body in sequence to obtain the SrTiO3-based giant dielectric ceramic material with dual donors co-doped at the A and B positions; the sintering is carried out in a nitrogen atmosphere.

[0013] Preferably, the conditions for the primary ball milling and the secondary ball milling independently include: a ball milling speed of 250 to 350 rpm, a ball milling time of 7 to 9 hours, and deionized water as the ball milling medium.

[0014] Preferably, the calcination temperature is 1100-1300° C., the holding time is 3-5 hours; the heating rate to the calcination temperature is 4-6° C. / min, and the calcination atmosphere is air.

[0015] Preferably, the binder is a polyvinyl alcohol solution, and the mass concentration of the polyvinyl alcohol solution is 3-5%; the amount of the binder is 1-2% of the mass of the synthetic powder; and the amount of water is 0.5-1% of the mass of the synthetic powder.

[0016] Preferably, the dry pressing pressure is 13-17 MPa; the diameter of the ceramic body is 8-12 mm, and the thickness is 1-3 mm.

[0017] Preferably, the debinding temperature is 550-650° C., and the holding time is 1-3 hours.

[0018] Preferably, the sintering temperature is 1475-1550° C., the holding time is 5-7 hours, and the nitrogen flow rate is 60-100 mL / min.

[0019] Preferably, the procedure for heating to the sintering temperature is: first heating to 1200°C at a rate of 4-6°C / min, then heating to 1400°C at a rate of 2-4°C / min, then heating to 1500°C at a rate of 1-3°C / min, and finally heating to the sintering temperature at a rate of 0.5-1.5°C / min.

[0020] The present invention also provides a SrTiO3-based giant dielectric ceramic material prepared by the preparation method described in the above scheme with dual donors co-doped at the A and B positions.

[0021] Preferably, the dielectric constant of the SrTiO3-based giant dielectric ceramic material co-doped with dual donors at the A and B positions is in the range of 94000 to 170000 at a test frequency of 1kHz at room temperature, and the dielectric loss is in the range of 0.076 to 0.40; the dielectric constant is in the range of 10000 to 113000 at a test frequency of 1MHz at room temperature, and the dielectric loss is in the range of 0.026 to 0.55; the temperature coefficient of the dielectric constant in the range of 30 to 200°C is less than |15%|.

[0022] The present invention provides a preparation method of a SrTiO3-based giant dielectric ceramic material co-doped with dual donors at the A and B positions, comprising the following steps: (1) ball-milling SrCO3, TiO2, Nb2O5 and Sm2O3 according to the ratio in formula I (see above), drying and calcining the obtained primary ball-milled material to obtain a synthetic powder; (2) ball-milling the synthetic powder for a second time, followed by screening and drying in sequence to obtain a secondary ball-milled material; (3) mixing the secondary ball-milled material, a binder and water, and then aging, granulating and dry-pressing in sequence to obtain a ceramic green body; (4) debinding and sintering the ceramic green body in sequence to obtain the SrTiO3-based giant dielectric ceramic material co-doped with dual donors at the A and B positions; the sintering is carried out in a nitrogen atmosphere. The present invention uses a double donor co-doping method of Sm at the Sr (A) site and Nb at the Ti (B) site and nitrogen sintering to make the ceramic have semiconducting grains and insulating grain boundaries, thereby enhancing the Maxwell-Wagner interface polarization strength, thereby making Sr 1-1.5x Sm x Ti 0.097 Nb0.003 O3 (0 < x ≤ 0.018) has a giant dielectric effect. The present invention, through sintering in a nitrogen atmosphere, can produce a SrTiO3-based giant dielectric ceramic material with dual donors co-doped at the A and B positions. This ceramic material exhibits excellent temperature stability in dielectric constant, meeting the demand for dielectric materials for miniaturized electronic components. Furthermore, the present invention uses relatively low amounts of the dopants Nb2O5 and Sm2O3, reducing production costs. Furthermore, the preparation method provided by the present invention is simple, reproducible, has a high yield, and is relatively low in cost, making it suitable for commercial production.

[0023] The results of the embodiment show that when x=0.015, the dielectric constant of the obtained SrTiO3-based giant dielectric ceramic material co-doped with dual donors at the A and B sites is ∼163,000 and the dielectric loss is ∼0.076 at room temperature and a test frequency of 1 kHz. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 Sr was obtained by sintering at 1550℃ for 6h in nitrogen atmosphere. 1-1.5x Sm x Ti 0.097 Nb 0.003 XRD pattern of O3 (0<x≤0.018) ceramic material;

[0025] Figure 2 Sr was obtained by sintering at 1550℃ for 6h in nitrogen atmosphere. 1-1.5x Sm x Ti 0.097 Nb 0.003 Surface morphology of O3 (0<x≤0.018) ceramic materials, where: (a) pure SrTiO3, (b) x=0, (c) x=0.003, (d) x=0.006, (e) x=0.009, (f) x=0.012, (g) x=0.015, (h) x=0.018;

[0026] Figure 3 Sr was obtained by sintering at 1550℃ for 6h in nitrogen atmosphere. 1-1.5x Sm x Ti 0.097 Nb 0.003 Frequency variations of dielectric properties of O3 (0 < x ≤ 0.018) ceramic materials, including: (a) frequency variations of dielectric constant at room temperature, (b) frequency variations of dielectric loss at room temperature, and (c) frequency variations of dielectric properties at room temperature and 1 kHz as a function of doping level.

[0027] Figure 4 Sr was obtained by sintering at 1550℃ for 6h in nitrogen atmosphere. 1-1.5x Sm x Ti 0.097 Nb0.003 The dielectric properties of O3 (0<x≤0.018) ceramic materials vary with temperature, including: (a) the variation of dielectric constant with temperature at room temperature, (b) the variation of dielectric loss with temperature at room temperature, and (c) the temperature coefficient of dielectric constant. DETAILED DESCRIPTION

[0028] The present invention provides a method for preparing a SrTiO3-based giant dielectric ceramic material co-doped with dual donors at A and B sites, comprising the following steps:

[0029] (1) SrCO3, TiO2, Nb2O5 and Sm2O3 are ball-milled according to the ratio in formula I, and the obtained ball-milled material is dried and calcined to obtain a synthetic powder;

[0030] Sr 1-1.5x Sm x Ti 0.097 Nb 0.003 O3 formula I;

[0031] In formula I: the value range of x is 0<x≤0.018;

[0032] (2) ball-milling the synthetic powder for a second time, followed by sieving and drying to obtain a second ball-milled material;

[0033] (3) mixing the secondary ball mill material, the binder and water, and then performing aging, granulation and dry pressing in sequence to obtain a ceramic body;

[0034] (4) Debinding and sintering the ceramic body in sequence to obtain the SrTiO3-based giant dielectric ceramic material with dual donors co-doped at the A and B positions; the sintering is carried out in a nitrogen atmosphere.

[0035] According to the present invention, SrCO3, TiO2, Nb2O5 and Sm2O3 are ball-milled once according to the ratio in formula I, and the obtained ball-milled material is dried and calcined to obtain synthetic powder. In the present invention, the value range of x in Formula I is preferably 0.003, 0.006, 0.009, 0.012, 0.015 or 0.018, more preferably 0.015; the purity of the SrCO3 is preferably above 99%, the purity of the TiO2 is preferably above 99%, the purity of the Sm2O3 is preferably above 99.99%, and the purity of the Nb2O5 is preferably above 99.99%; the conditions for the single ball milling preferably include: a ball milling speed of 250 to 350 rpm, more preferably 300 rpm, a ball milling time of 7 to 9 h, more preferably 8 h, and a ball milling medium of deionized water; the ball milling device is preferably a planetary ball mill, and the ball milling jar used for the ball milling is preferably a polytetrafluoroethylene ball milling jar; the present invention has no special requirements for the drying conditions, and drying in an oven is sufficient.

[0036] In the present invention, the calcination temperature is preferably 1150-1250°C, more preferably 1200°C, and the holding time is preferably 3-5 hours, more preferably 4 hours. The heating rate to the calcination temperature is preferably 4-6°C / min, more preferably 5°C / min. In a specific embodiment of the present invention, the dried primary milled material is preferably placed in an alumina crucible and then calcined in a muffle furnace.

[0037] After obtaining the synthetic powder, the present invention performs secondary ball milling on the synthetic powder, followed by screening and drying to obtain a secondary ball milled material. In the present invention, the secondary ball milling conditions preferably include: a ball milling speed of 250 to 350 rpm, more preferably 300 rpm, a ball milling time of 7 to 9 hours, more preferably 8 hours, and deionized water as the ball milling medium; the mesh size of the sieve used for screening is preferably 500 mesh; the present invention has no special requirements for the drying conditions, and drying in an oven is sufficient.

[0038] After obtaining the secondary ball mill material, the present invention sequentially mixes the secondary ball mill material, a binder, and water, and then performs aging, granulation, and dry pressing to obtain a ceramic green body. In the present invention, the binder is preferably a polyvinyl alcohol solution, and the mass concentration of the polyvinyl alcohol solution is preferably 3-5%, more preferably 4%; the amount of the binder is preferably 1-2% of the mass of the synthetic powder, and the amount of the water is preferably 0.5-1% of the mass of the synthetic powder; the water is preferably deionized water; the aging time is preferably 8-24 hours, and the aging temperature is preferably room temperature; the present invention has no special requirements for the granulation, and conditions well known in the art can be used; the pressure of the dry pressing is preferably 13-17 MPa, more preferably 15 MPa; the diameter of the ceramic green body is preferably 8-12 mm, more preferably 10 mm, and the thickness is preferably 1-2 mm.

[0039] After obtaining the ceramic green body, the present invention sequentially debinds and sinters the ceramic green body to obtain the SrTiO3-based giant dielectric ceramic material co-doped with dual donors at the A and B sites; the sintering is performed in a nitrogen atmosphere. In the present invention, the debinding temperature is preferably 550-650°C, more preferably 600°C, and the holding time of the debinding is preferably 1.5-2.5h, more preferably 2h; the debinding is preferably carried out in a muffle furnace; the sintering temperature is preferably 1500-1550°C, more preferably 1525°C, and the holding time of the sintering is preferably 5-7h, more preferably 5.5-6.5h, and further preferably 6h. The sintering atmosphere is nitrogen, and the flow rate of the nitrogen is preferably 60-100mL / min, more preferably 80mL / min; the procedure for heating to the sintering temperature is preferably: first heating to 1200°C at a rate of 4-6°C / min, then heating to 1400°C at a rate of 2-4°C / min, then heating to 1500°C at a rate of 1-3°C / min, and finally heating to the sintering temperature at a rate of 0.5-1.5°C / min; the sintering is preferably carried out in a tubular furnace.

[0040] The present invention also provides a SrTiO3-based giant dielectric ceramic material with dual donors co-doped at the A and B positions, prepared by the preparation method described in the above scheme; the chemical formula of the SrTiO3-based giant dielectric ceramic material with dual donors co-doped at the A and B positions is shown in Formula I:

[0041] Sr 1-1.5x Sm x Ti 0.097 Nb 0.003 O3 formula I;

[0042] In formula I: the value range of x is 0<x≤0.018.

[0043] In the present invention, the SrTiO3-based giant dielectric ceramic material with dual donors co-doped at the A and B sites has a dielectric constant ranging from 94,000 to 170,000 at room temperature and a test frequency of 1 kHz, and a dielectric loss ranging from 0.076 to 0.40; the dielectric constant ranges from 10,000 to 113,000 at room temperature and a test frequency of 1 MHz, and the dielectric loss ranges from 0.026 to 0.55; the temperature coefficient of the dielectric constant within the range of 30 to 200°C is less than |15%|; specifically, when x = 0.015, at room temperature and a test frequency of 1 kHz, the dielectric constant of the resulting ceramic material is 163,000 and the dielectric loss is 0.076. The SrTiO3-based giant dielectric ceramic material with dual donors co-doped at the A and B sites provided by the present invention has a giant dielectric constant and good temperature stability of the dielectric constant, meeting the demand for dielectric materials for miniaturization of electronic components and energy storage devices, and has broad application prospects.

[0044] The technical solutions in the present application will be clearly and completely described below in combination with the embodiments in the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all the other embodiments obtained by a person of ordinary skill in the art without creative effort belong to the protection scope of the present application.

[0045] Embodiment 1

[0046] Step 1: SrCO3 (purity 99%), TiO2 (purity 99%), Nb2O5 (purity 99.99%) and Sm2O3 (purity 99.99%) were used as starting materials, and the raw materials were weighed according to the chemical formula Sr 1-1.5x Sm x Ti 0.097 Nb 0.003 O3 (x = 0) with a total mass of 30 g. The weighed raw materials were added to a polytetrafluoroethylene ball mill tank with deionized water as the ball milling medium, and were mixed and ball milled on a planetary ball mill at a rotation speed of 300 rpm for 8 h, and then were placed in an oven for drying.

[0047] Step 2: The dried powder in step 1 was loaded into an alumina crucible, and was heated in a muffle furnace at a heating rate of 5 ℃ / min to 1200 ℃ for 4 h to obtain a synthesized powder, and the same process as in step 1 was used for secondary ball milling, and the powder was dried after being sieved through a 500 mesh sieve.

[0048] Step 3: 0.5 g of a 4 wt.% PVA solution and 0.2 g of deionized water were added to the powder obtained in step 2, and were aged and granulated, and were dry pressed to form a ceramic green body with a diameter of 10 mm and a thickness of 2 mm at a dry pressing pressure of 15 MPa. The ceramic green body was placed in a muffle furnace and was heated to 600 ℃ for 2 h to remove the binder.

[0049] Step 4: The ceramic green body obtained in step 3 was placed in a tube furnace, and was heated to 1200 ℃ at a nitrogen flow rate of 80 mL / min and a heating rate of 5 ℃ / min, then was heated to 1400 ℃ at a heating rate of 3 ℃ / min, then was heated to 1500 ℃ at a heating rate of 2 ℃ / min, and finally was heated to 1550 ℃ at a heating rate of 1 ℃ / min and was kept at 1550 ℃ for 6 h to obtain a double-donor co-doped SrTiO3-based giant dielectric ceramic material.

[0050] The sintered ceramic sheet was polished on both sides and was coated with silver electrodes, and was placed in a muffle furnace and was heated to 550 ℃ for 15 min to burn the electrodes. The dielectric property test was performed using an Agilent 4294A impedance analyzer. The dielectric constant of the ceramic material was about 93600, and the dielectric loss was about 0.17 at room temperature and a test frequency of 1 kHz.

[0051] Embodiment 2

[0052] Step 1: Using SrCO3 (purity 99%), TiO2 (purity 99%), Nb2O5 (purity 99.99%) and Sm2O3 (purity 99.99%) as starting materials, according to the chemical formula Sr 1-1.5x Sm x Ti 0.097 Nb 0.003 O3 (x = 0.003) weighed the raw materials, with a total mass of 30 g, added the weighed raw materials into a polytetrafluoroethylene ball mill with deionized water as the ball milling medium, and mixed and ball-milled on a planetary ball mill at a speed of 300 rpm for 8 h, and then placed in an oven for drying.

[0053] Step 2: The powder dried in step 1 is placed in an alumina crucible, heated to 1200°C in a muffle furnace at a heating rate of 5°C / min and kept warm for 4 hours to synthesize the powder, and then ball-milled twice using the same process as step 1, passed through a 500-mesh sieve, and then dried.

[0054] Step 3: Add 0.5g of a 4wt% PVA solution and 0.2g of deionized water to the powder obtained in Step 2, granulate, and dry-press at a pressure of 15MPa to form a ceramic body with a diameter of 10mm and a thickness of 2mm. Place the ceramic body in a muffle furnace and heat it to 600°C for 2 hours to remove binder.

[0055] Step 4: Place the ceramic body obtained in step 3 in a tubular furnace, heat it to 1200°C at a nitrogen flow rate of 80 mL / min at a heating rate of 5°C / min, then heat it to 1400°C at 3°C / min, then heat it to 1500°C at 2°C / min, and finally heat it to 1550°C at 1°C / min and keep it warm for 6 hours to obtain a SrTiO3-based giant dielectric ceramic material with dual donors co-doped at the A and B positions.

[0056] The sintered ceramic discs were polished on both sides and coated with silver electrodes. The electrodes were then heated to 550°C in a muffle furnace and held for 15 minutes to sinter the electrodes. Dielectric properties were tested using an Agilent 4294A impedance analyzer. At room temperature and a test frequency of 1 kHz, the dielectric constant of the ceramic material was ~135,000, and the dielectric loss was ~0.15.

[0057] Example 3

[0058] Step 1: Using SrCO3 (purity 99%), TiO2 (purity 99%), Nb2O5 (purity 99.99%) and Sm2O3 (purity 99.99%) as starting materials, according to the chemical formula Sr 1-1.5x Sm x Ti 0.097 Nb 0.003O3 (x = 0.006) weighed the raw materials, with a total mass of 30 g, added the weighed raw materials into a polytetrafluoroethylene ball mill with deionized water as the ball milling medium, and mixed and ball-milled on a planetary ball mill at a speed of 300 rpm for 8 h, and then placed in an oven for drying.

[0059] Step 2: The powder dried in step 1 is placed in an alumina crucible, heated to 1200°C in a muffle furnace at a heating rate of 5°C / min and kept warm for 4 hours to synthesize the powder, and then ball-milled twice using the same process as step 1, passed through a 500-mesh sieve, and then dried.

[0060] Step 3: Add 0.5g of a 4wt% PVA solution and 0.2g of deionized water to the powder obtained in Step 2, granulate, and dry-press at a pressure of 15MPa to form a ceramic body with a diameter of 10mm and a thickness of 2mm. Place the ceramic body in a muffle furnace and heat it to 600°C for 2 hours to remove binder.

[0061] Step 4: Place the ceramic body obtained in step 3 in a tubular furnace, heat it to 1200°C at a nitrogen flow rate of 80 mL / min at a heating rate of 5°C / min, then heat it to 1400°C at 3°C / min, then heat it to 1500°C at 2°C / min, and finally heat it to 1550°C at 1°C / min and keep it warm for 6 hours to obtain a SrTiO3-based giant dielectric ceramic material with dual donors co-doped at the A and B positions.

[0062] The sintered ceramic discs were polished on both sides and coated with silver electrodes. The electrodes were then heated to 550°C in a muffle furnace and held for 15 minutes to sinter the electrodes. Dielectric properties were tested using an Agilent 4294A impedance analyzer. At room temperature and a test frequency of 1 kHz, the dielectric constant of the ceramic material was ~143,000, and the dielectric loss was ~0.14.

[0063] Example 4

[0064] Step 1: Using SrCO3 (purity 99%), TiO2 (purity 99%), Nb2O5 (purity 99.99%) and Sm2O3 (purity 99.99%) as starting materials, according to the chemical formula Sr 1-1.5x Sm x Ti 0.097 Nb 0.003 O3 (x = 0.009) weighed the raw materials, with a total mass of 30 g, added the weighed raw materials into a polytetrafluoroethylene ball mill with deionized water as the ball milling medium, and mixed and ball-milled on a planetary ball mill at a speed of 300 rpm for 8 h, and then placed in an oven for drying.

[0065] Step 2: The powder dried in step 1 is placed in an alumina crucible, heated to 1200°C in a muffle furnace at a heating rate of 5°C / min and kept warm for 4 hours to synthesize the powder, and then ball-milled twice using the same process as step 1, passed through a 500-mesh sieve, and then dried.

[0066] Step 3: Add 0.5g of a 4wt% PVA solution and 0.2g of deionized water to the powder obtained in Step 2, granulate, and dry-press at a pressure of 15MPa to form a ceramic body with a diameter of 10mm and a thickness of 2mm. Place the ceramic body in a muffle furnace and heat it to 600°C for 2 hours to remove binder.

[0067] Step 4: Place the ceramic body obtained in step 3 in a tubular furnace, heat it to 1200°C at a nitrogen flow rate of 80 mL / min at a heating rate of 5°C / min, then heat it to 1400°C at 3°C / min, then heat it to 1500°C at 2°C / min, and finally heat it to 1550°C at 1°C / min and keep it warm for 6 hours to obtain a SrTiO3-based giant dielectric ceramic material with dual donors co-doped at the A and B positions.

[0068] The sintered ceramic discs were polished on both sides and coated with silver electrodes. The electrodes were then heated to 550°C in a muffle furnace and held for 15 minutes to sinter the electrodes. Dielectric properties were tested using an Agilent 4294A impedance analyzer. At room temperature and a test frequency of 1 kHz, the dielectric constant of the ceramic material was ~131,000, and the dielectric loss was ~0.099.

[0069] Example 5

[0070] Step 1: Using SrCO3 (purity 99%), TiO2 (purity 99%), Nb2O5 (purity 99.99%) and Sm2O3 (purity 99.99%) as starting materials, according to the chemical formula Sr 1-1.5x Sm x Ti 0.097 Nb 0.003 O3 (x = 0.012) weighed the raw materials, with a total mass of 30 g, added the weighed raw materials into a polytetrafluoroethylene ball mill with deionized water as the ball milling medium, and mixed and ball-milled on a planetary ball mill at a speed of 300 rpm for 8 h, and then placed in an oven for drying.

[0071] Step 2: The powder dried in step 1 is placed in an alumina crucible, heated to 1200°C in a muffle furnace at a heating rate of 5°C / min and kept warm for 4 hours to synthesize the powder, and then ball-milled twice using the same process as step 1, passed through a 500-mesh sieve, and then dried.

[0072] Step 3: Add 0.5g of a 4wt% PVA solution and 0.2g of deionized water to the powder obtained in Step 2, granulate, and dry-press at a pressure of 15MPa to form a ceramic body with a diameter of 10mm and a thickness of 2mm. Place the ceramic body in a muffle furnace and heat it to 600°C for 2 hours to remove binder.

[0073] Step 4: Place the ceramic body obtained in step 3 in a tubular furnace, heat it to 1200°C at a nitrogen flow rate of 80 mL / min at a heating rate of 5°C / min, then heat it to 1400°C at 3°C / min, then heat it to 1500°C at 2°C / min, and finally heat it to 1550°C at 1°C / min and keep it warm for 6 hours to obtain a SrTiO3-based giant dielectric ceramic material with dual donors co-doped at the A and B positions.

[0074] The sintered ceramic discs were polished on both sides and coated with silver electrodes. The electrodes were then heated to 550°C in a muffle furnace and held for 15 minutes to sinter the electrodes. Dielectric properties were tested using an Agilent 4294A impedance analyzer. At room temperature and a test frequency of 1 kHz, the dielectric constant of the ceramic material was ~160,000, and the dielectric loss was ~0.11.

[0075] Example 6

[0076] Step 1: Using SrCO3 (purity 99%), TiO2 (purity 99%), Nb2O5 (purity 99.99%) and Sm2O3 (purity 99.99%) as starting materials, according to the chemical formula Sr 1-1.5x Sm x Ti 0.097 Nb 0.003 O3 (x = 0.015) weighed the raw materials, with a total mass of 30 g, added the weighed raw materials into a polytetrafluoroethylene ball mill with deionized water as the ball milling medium, and mixed and ball-milled on a planetary ball mill at a speed of 300 rpm for 8 h, and then placed in an oven for drying.

[0077] Step 2: The powder dried in step 1 is placed in an alumina crucible, heated to 1200°C in a muffle furnace at a heating rate of 5°C / min and kept warm for 4 hours to synthesize the powder, and then ball-milled twice using the same process as step 1, passed through a 500-mesh sieve, and then dried.

[0078] Step 3: Add 0.5g of a 4wt% PVA solution and 0.2g of deionized water to the powder obtained in Step 2, granulate, and dry-press at a pressure of 15MPa to form a ceramic body with a diameter of 10mm and a thickness of 2mm. Place the ceramic body in a muffle furnace and heat it to 600°C for 2 hours to remove binder.

[0079] Step 4: Place the ceramic body obtained in step 3 in a tubular furnace, heat it to 1200°C at a nitrogen flow rate of 80 mL / min at a heating rate of 5°C / min, then heat it to 1400°C at 3°C / min, then heat it to 1500°C at 2°C / min, and finally heat it to 1550°C at 1°C / min and keep it warm for 6 hours to obtain a SrTiO3-based giant dielectric ceramic material with dual donors co-doped at the A and B positions.

[0080] The sintered ceramic discs were polished on both sides and coated with silver electrodes. The electrodes were then heated to 550°C in a muffle furnace and held for 15 minutes to sinter the electrodes. Dielectric properties were tested using an Agilent 4294A impedance analyzer. At room temperature and a test frequency of 1 kHz, the dielectric constant of the ceramic material was ~163,000, and the dielectric loss was ~0.076.

[0081] Example 7

[0082] Step 1: Using SrCO3 (purity 99%), TiO2 (purity 99%), Nb2O5 (purity 99.99%) and Sm2O3 (purity 99.99%) as starting materials, according to the chemical formula Sr 1-1.5x Sm x Ti 0.097 Nb 0.003 O3 (x = 0.018) weighed the raw materials, with a total mass of 30 g, added the weighed raw materials into a polytetrafluoroethylene ball mill with deionized water as the ball milling medium, and mixed and ball-milled on a planetary ball mill at a speed of 300 rpm for 8 h, and then placed in an oven for drying.

[0083] Step 2: The powder dried in step 1 is placed in an alumina crucible, heated to 1200°C in a muffle furnace at a heating rate of 5°C / min and kept warm for 4 hours to synthesize the powder, and then ball-milled twice using the same process as step 1, passed through a 500-mesh sieve, and then dried.

[0084] Step 3: Add 0.5g of a 4wt% PVA solution and 0.2g of deionized water to the powder obtained in Step 2, granulate, and dry-press at a pressure of 15MPa to form a ceramic body with a diameter of 10mm and a thickness of 2mm. Place the ceramic body in a muffle furnace and heat it to 600°C for 2 hours to remove binder.

[0085] Step 4: Place the ceramic body obtained in step 3 in a tubular furnace, heat it to 1200°C at a nitrogen flow rate of 80 mL / min at a heating rate of 5°C / min, then heat it to 1400°C at 3°C / min, then heat it to 1500°C at 2°C / min, and finally heat it to 1550°C at 1°C / min and keep it warm for 6 hours to obtain a SrTiO3-based giant dielectric ceramic material with dual donors co-doped at the A and B positions.

[0086] The sintered ceramic discs were polished on both sides and coated with silver electrodes. The electrodes were then heated to 550°C in a muffle furnace and held for 15 minutes to sinter the electrodes. Dielectric properties were tested using an Agilent 4294A impedance analyzer. At room temperature and a test frequency of 1 kHz, the dielectric constant of the ceramic material was ~170,000, and the dielectric loss was ~0.40.

[0087] Example 8

[0088] Step 1: Using SrCO3 (purity 99%), TiO2 (purity 99%), Nb2O5 (purity 99.99%) and Sm2O3 (purity 99.99%) as starting materials, according to the chemical formula Sr 1-1.5x Sm x Ti 0.097 Nb 0.003 O3 (x = 0.015) weighed the raw materials, with a total mass of 30 g, added the weighed raw materials into a polytetrafluoroethylene ball mill with deionized water as the ball milling medium, and mixed and ball-milled on a planetary ball mill at a speed of 300 rpm for 8 h, and then placed in an oven for drying.

[0089] Step 2: The powder dried in step 1 is placed in an alumina crucible, heated to 1200°C in a muffle furnace at a heating rate of 5°C / min and kept warm for 4 hours to synthesize the powder, and then ball-milled twice using the same process as step 1, passed through a 500-mesh sieve, and then dried.

[0090] Step 3: Add 0.5g of a 4wt% PVA solution and 0.2g of deionized water to the powder obtained in Step 2, granulate, and dry-press at a pressure of 15MPa to form a ceramic body with a diameter of 10mm and a thickness of 2mm. Place the ceramic body in a muffle furnace and heat it to 600°C for 2 hours to remove binder.

[0091] Step 4: Place the ceramic body obtained in step 3 in a tubular furnace, heat it to 1200°C at a nitrogen flow rate of 80 mL / min at a heating rate of 5°C / min, then heat it to 1400°C at 3°C / min, heat it to 1500°C at 2°C / min, and finally heat it to 1525°C at 1°C / min and keep it warm for 6 hours to obtain a SrTiO3-based giant dielectric ceramic material with dual donors co-doped at the A and B positions.

[0092] The sintered ceramic discs were polished on both sides and coated with silver electrodes. The electrodes were then heated to 550°C in a muffle furnace and held for 15 minutes to sinter the electrodes. Dielectric properties were tested using an Agilent 4294A impedance analyzer. At room temperature and a test frequency of 1 kHz, the dielectric constant of the ceramic material was ~154,000, and the dielectric loss was ~0.095.

[0093] Example 9

[0094] Step 1: Using SrCO3 (purity 99%), TiO2 (purity 99%), Nb2O5 (purity 99.99%) and Sm2O3 (purity 99.99%) as starting materials, according to the chemical formula Sr 1-1.5x Sm x Ti 0.097 Nb 0.003 O3 (x = 0.015) weighed the raw materials, with a total mass of 30 g, added the weighed raw materials into a polytetrafluoroethylene ball mill with deionized water as the ball milling medium, and mixed and ball-milled on a planetary ball mill at a speed of 300 rpm for 8 h, and then placed in an oven for drying.

[0095] Step 2: The powder dried in step 1 is placed in an alumina crucible, heated to 1200°C in a muffle furnace at a heating rate of 5°C / min and kept warm for 4 hours to synthesize the powder, and then ball-milled twice using the same process as step 1, passed through a 500-mesh sieve, and then dried.

[0096] Step 3: Add 0.5g of a 4wt% PVA solution and 0.2g of deionized water to the powder obtained in Step 2, granulate, and dry-press at a pressure of 15MPa to form a ceramic body with a diameter of 10mm and a thickness of 2mm. Place the ceramic body in a muffle furnace and heat it to 600°C for 2 hours to remove binder.

[0097] Step 4: Place the ceramic body obtained in step 3 in a tubular furnace, heat it to 1200°C at a nitrogen flow rate of 80 mL / min at a heating rate of 5°C / min, then heat it to 1400°C at a rate of 3°C / min, and then heat it to 1500°C at a rate of 2°C / min and keep it warm for 6 hours to obtain a SrTiO3-based giant dielectric ceramic material with dual donors co-doped at the A and B positions.

[0098] The sintered ceramic discs were polished on both sides and coated with silver electrodes. The electrodes were then heated to 550°C in a muffle furnace and held for 15 minutes to sinter the electrodes. Dielectric properties were tested using an Agilent 4294A impedance analyzer. At room temperature and a test frequency of 1 kHz, the dielectric constant of the ceramic material was ~140,000, and the dielectric loss was ~0.15.

[0099] Example 10

[0100] Step 1: Using SrCO3 (purity 99%), TiO2 (purity 99%), Nb2O5 (purity 99.99%) and Sm2O3 (purity 99.99%) as starting materials, according to the chemical formula Sr 1-1.5x Sm x Ti 0.097 Nb 0.003O3 (x = 0.015) weighed a total mass of 30g of raw materials, added the weighed raw materials into a polytetrafluoroethylene ball mill with deionized water as the ball milling medium, and mixed and ball-milled on a planetary ball mill at a speed of 300rpm for 8h and then placed in an oven for drying.

[0101] Step 2: The powder dried in step 1 is placed in an alumina crucible, heated to 1200°C in a muffle furnace at a heating rate of 5°C / min and kept warm for 4 hours to synthesize the powder, and then ball-milled twice using the same process as step 1, passed through a 500-mesh sieve, and then dried.

[0102] Step 3: Add 0.5g of a 4wt% PVA solution and 0.2g of deionized water to the powder obtained in Step 2, granulate, and dry-press at a pressure of 15MPa to form a ceramic body with a diameter of 10mm and a thickness of 2mm. Place the ceramic body in a muffle furnace and heat it to 600°C for 2 hours to remove binder.

[0103] Step 4: Place the ceramic body obtained in step 3 in a tubular furnace, heat it to 1200°C at a nitrogen flow rate of 80 mL / min at a heating rate of 5°C / min, then heat it to 1400°C at a rate of 3°C / min, and then heat it to 1475°C at a rate of 2°C / min and keep it warm for 6 hours to obtain a SrTiO3-based giant dielectric ceramic material with dual donors co-doped at the A and B positions.

[0104] The sintered ceramic discs were polished on both sides and coated with silver electrodes. The electrodes were then heated to 550°C in a muffle furnace and held for 15 minutes to sinter the electrodes. Dielectric properties were tested using an Agilent 4294A impedance analyzer. At room temperature and a test frequency of 1 kHz, the dielectric constant of the ceramic material was ~135,000, and the dielectric loss was ~0.13.

[0105] Performance testing:

[0106] 1. The dielectric properties of the ceramic materials prepared in Examples 1 to 10 are summarized in Table 1.

[0107] Table 1 Dielectric properties of samples prepared in Example 1 to Comparative Example 2

[0108]

[0109] According to the data in Table 1, it can be seen that when the value of x is in the range of 0<x≤0.18 and the sintering temperature is in the range of 1475~1550℃, SrTiO3-based giant dielectric ceramic materials with giant dielectric constant and low dielectric loss can be obtained.

[0110] 2. XRD test

[0111] Figure 1SrTiO3+x%Sm2O3 1-1.5x Sm x Ti 0.097 Nb 0.003 XRD patterns of SrTiO3+x%Sm2O3(0 Figure 1 It can be seen that all samples have cubic perovskite structure, which is in good agreement with PDF#84-0444, and no second phase is detected, indicating that Nb and Sm are completely solid-solved into the SrTiO3 lattice.

[0112] 3. Morphology test

[0113] Figure 2 SEM images of SrTiO3+x%Sm2O3(0 1-1.5x Sm x Ti 0.097 Nb 0.003 SEM images of SrTiO3+x%Sm2O3(0 Figure 2 It can be seen from (b) in FIG. 6 that when x = 0, the grain size is obviously larger than that of pure SrTiO3, and then with the introduction of Sm, the grain size first becomes smaller and then larger, and the grain boundary becomes blurred, which is due to the gradual decrease of Sr / Ti with the increase of the non-equivalent doping concentration of Sm in Sr site. When Ti is excessive, liquid phase sintering occurs at the grain boundary, so with the increase of the doping concentration, the grain boundary gradually becomes blurred, and the grains are difficult to distinguish.

[0114] 4. Dielectric properties of ceramic materials with frequency

[0115] Figure 3 Dielectric properties of SrTiO3+x%Sm2O3(0 1-1.5x Sm x Ti 0.097 Nb 0.003 Dielectric properties of SrTiO3+x%Sm2O3(0 Figure 3 It can be seen from (a) and (b) in FIG. 8 that the dielectric properties of samples with x = 0.003-0.015 exhibit lower frequency dependence at low frequencies. When the frequency is increased to 10 5At Hz, the dielectric constant drops sharply, while the corresponding dielectric loss shows the opposite trend. This result is typical of Maxwell-Wagner interface polarization behavior. The dielectric response at low frequencies should be described as the influence of grain boundaries, while the dielectric response at high frequencies should be attributed to the contribution of grains. The dielectric properties of samples with x = 0 and 0.018 are influenced by the electron pinning effect, and the frequency dependence of the dielectric constant is low. Figure 3 From (c), it can be seen that the best dielectric performance is obtained when x = 0.015, with a dielectric constant of ∼163,000 and a dielectric loss of ∼0.076.

[0116] 5. Changes in dielectric properties of ceramic materials with temperature

[0117] Figure 4 Sr was obtained by sintering at 1550℃ for 6h in nitrogen atmosphere. 1-1.5x Sm x Ti 0.097 Nb 0.003 The changes of dielectric properties of O3 (0<x≤0.018) ceramic materials with temperature, including: (a) the change of dielectric constant with temperature at room temperature, (b) the change of dielectric loss with temperature at room temperature, (c) the temperature coefficient of dielectric constant. Figure 4 It can be seen that the temperature stability of the dielectric properties of samples with x = 0.003 to 0.015 is significantly improved compared to pure SrTiO3, and samples with x = 0 and 0.018. This indicates that the appropriate doping concentration will form a heterogeneous structure at the grain boundary, enhance the sample's IBLC effect, and thus improve the temperature stability of the dielectric properties.

[0118] In summary, the present invention provides a SrTiO3-based giant dielectric ceramic material co-doped with dual donors at the A and B positions and a preparation method thereof, wherein the chemical formula is Sr 1-1.5x Sm x Ti 0.097 Nb 0.003 O3 (0<x≤0.018), this material can obtain a giant dielectric constant when sintered in a nitrogen atmosphere. When x=0.015, a giant dielectric constant of ~163000 and a low dielectric loss of ~0.076 are obtained. The temperature coefficient of the dielectric constant is less than |15%| in the temperature range of 30~200℃, and the temperature stability is good.

[0119] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A method for preparing a SrTiO3-based giant dielectric ceramic material with dual donors co-doped at the A and B sites, characterized in that: The following steps are involved: (1) SrCO3, TiO2, Nb2O5 and Sm2O3 are ball-milled according to the ratio in formula I, and the obtained ball-milled material is dried and calcined to obtain a synthetic powder; Sr 1-1.5x Sm x Ti 0.097 Nb 0.003 O3 formula I; In formula (I), the value range of x is 0.003≤x≤0.018; (2) ball-milling the synthetic powder for a second time, followed by sieving and drying to obtain a second ball-milled material; (3) mixing the secondary ball mill material, the binder and water, and then performing aging, granulation and dry pressing in sequence to obtain a ceramic body; (4) Debinding and sintering the ceramic body in sequence to obtain the SrTiO3-based giant dielectric ceramic material with dual donors co-doped at the A and B positions; the sintering is carried out in a nitrogen atmosphere.

2. The preparation method according to claim 1, characterized in that The conditions of the primary ball milling and the secondary ball milling independently include: a ball milling speed of 250 to 350 rpm, a ball milling time of 7 to 9 hours, and a ball milling medium of deionized water.

3. The preparation method according to claim 1, characterized in that The calcination temperature is 1100-1300° C., and the holding time is 3-5 hours. The heating rate to the calcination temperature is 4-6° C. / min, and the calcination atmosphere is air.

4. The preparation method according to claim 1, characterized in that The binder is a polyvinyl alcohol solution with a mass concentration of 3-5%. The amount of the binder is 1-2% of the mass of the synthetic powder. The amount of water is 0.5-1% of the mass of the synthetic powder.

5. The preparation method according to claim 1, characterized in that The dry pressing pressure is 13-17 MPa; the diameter of the ceramic body is 8-12 mm, and the thickness is 1-3 mm.

6. The preparation method according to claim 1, characterized in that The debinding temperature is 550-650° C., and the heat preservation time is 1-3 hours.

7. The preparation method according to claim 1, characterized in that The sintering temperature is 1475-1550° C., the holding time is 5-7 hours, and the nitrogen flow rate is 60-100 mL / min.

8. The preparation method according to claim 1, characterized in that The procedure for heating to the sintering temperature is: first heating to 1200°C at a rate of 4-6°C / min, then heating to 1400°C at a rate of 2-4°C / min, then heating to 1500°C at a rate of 1-3°C / min, and finally heating to the sintering temperature at a rate of 0.5-1.5°C / min.

9. The SrTiO3-based giant dielectric ceramic material prepared by the preparation method according to any one of claims 1 to 8 with dual donors co-doped at the A and B sites.

10. The SrTiO3-based giant dielectric ceramic material with dual donors co-doped at the A and B sites according to claim 9, characterized in that: The dielectric constant of the SrTiO3-based giant dielectric ceramic material co-doped with dual donors at the A and B sites ranges from 94,000 to 170,000 at a test frequency of 1 kHz at room temperature, and the dielectric loss ranges from 0.076 to 0.40; the dielectric constant ranges from 10,000 to 113,000 at a test frequency of 1 MHz at room temperature, and the dielectric loss ranges from 0.026 to 0.55; and the temperature coefficient of the dielectric constant in the range of 30 to 200°C is less than |15%|.

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