Gadolinium-tantalum co-doped strontium titanate-based giant dielectric ceramic material and preparation method thereof

Abstract

The invention relates to the technical field of dielectric ceramics, and provides a gadolinium-tantalum co-doped strontium titanate-based giant dielectric ceramic material and a preparation method thereof. The gadolinium-tantalum co-doped strontium titanate-based giant dielectric ceramic material is obtained by co-doping a strontium titanate material with gadolinium and tantalum and sintering under a nitrogen condition. The gadolinium-tantalum co-doped strontium titanate-based giant dielectric ceramic material prepared by the method is stable in structure, grains are refined and grow more compactly through nitrogen atmosphere sintering, the types of defect structures in the material are richer through a double-element doping and atmosphere sintering process, and the dielectric property of the strontium titanate-based giant dielectric ceramic material is improved. The result of the embodiment shows that when x is equal to 0.015, the dielectric constant of the gadolinium-tantalum co-doped strontium titanate-based giant dielectric ceramic material is 320926 and the dielectric loss is 0.1119 at the room temperature and the test frequency of 1kHz.

Description

Technical Field

[0001] The present invention relates to the technical field of dielectric ceramics, and in particular to a gadolinium-tantalum co-doped strontium titanate-based giant dielectric ceramic material and a preparation method thereof. Background Art

[0002] With the rapid development of the modern electronic information industry, high-energy storage capacitors have gradually become an important research topic in the field of electronic information. To improve the energy storage performance, it is necessary to start from improving the dielectric constant. Giant dielectric ceramic materials have received extensive attention due to their high dielectric constant (ε r > 10 3 ).

[0003] Currently, there are mainly four types of substrate materials for the research of giant dielectric ceramic materials, namely CaCu3Ti4O 12 , metal oxides (NiO, TiO2), BaTiO3 and SrTiO3. CaCu3Ti4O 12 materials have good temperature stability of dielectric constant, but often have high dielectric losses. NiO materials have a dielectric constant of the order of 10 6 , but have high dielectric losses and are difficult to reduce. TiO2 materials have a high dielectric constant and low dielectric losses, but have a low breakdown strength. BaTiO3 materials have a ferroelectric phase transition near the Curie temperature and can only be applied in a specific temperature range. Compared with other materials, SrTiO3 materials have low dielectric losses, high breakdown strength and frequency / temperature stability over a wide frequency range. However, in practical applications, the dielectric constant of SrTiO3 materials far from meets the application requirements.

[0004] In summary, how to improve the dielectric constant of SrTiO3 materials is an urgent problem to be solved in this field and has broad research significance. Summary of the Invention

[0005] In view of this, the present invention provides a gadolinium-tantalum co-doped strontium titanate-based giant dielectric ceramic material and a preparation method thereof. The gadolinium-tantalum co-doped strontium titanate-based giant dielectric ceramic material provided by the present invention is a typical strontium titanate-based composite perovskite structure material, which has an extremely high dielectric constant and low dielectric losses, and is an ideal material for the development of high-energy storage capacitors.

[0006] To achieve the above invention object, the present invention provides the following technical solutions:

[0007] A preparation method of a gadolinium-tantalum co-doped strontium titanate-based giant dielectric ceramic material, comprising the following steps:

[0008] (1) According to the stoichiometric ratio in Formula I, strontium carbonate, titanium dioxide, gadolinium oxide and tantalum pentoxide are used for batching, and the obtained raw material powder is ball-milled once to obtain a mixed powder;

[0009] Sr 0.985 Gd 0.015 Ti 1-x Ta x O3 of formula I;

[0010] In formula I: 0 < x ≤ 0.02;

[0011] (2) Pre-synthesize the mixed powder, and then perform secondary ball milling to obtain ceramic powder.

[0012] (3) Mix the ceramic powder, binder, and water, and then perform grinding, pressing, aging, and pulverization in sequence to obtain ceramic particles; dry press the ceramic particles to form a ceramic green body.

[0013] (4) Debind the ceramic green body and then sinter it in a nitrogen atmosphere to obtain the gadolinium-tantalum co-doped strontium titanate-based giant dielectric ceramic material.

[0014] Preferably, the conditions of the primary ball milling and secondary ball milling independently include: the milling balls are zirconia balls, the milling medium is deionized water, the milling speed is 300 - 450 rpm, and the milling time is 7 - 9 h; after the primary ball milling and secondary ball milling, drying the obtained material is further included, and the temperature of the drying is 85 - 100 °C and the time is 20 - 24 h.

[0015] Preferably, the temperature of the pre-synthesis is 1150 - 1250 °C, the holding time is 3 - 5 h, and the heating program for heating to the temperature of the pre-synthesis is: first heat up to 500 °C at a rate of 8 - 12 °C / min, and then heat up to the temperature of the pre-synthesis at a rate of 4 - 6 °C / min; the atmosphere of the pre-synthesis is air.

[0016] Preferably, the binder is a polyvinyl alcohol solution; the concentration of the polyvinyl alcohol solution is 3 - 5 wt.%; the dosage of the binder is 1 - 2% of the mass of the ceramic powder; the dosage of the water is 0.5 - 1% of the mass of the ceramic powder.

[0017] Preferably, the dry pressing is carried out under a unidirectional pressure, and the unidirectional pressure of the dry pressing is 10 - 20 MPa; the diameter of the ceramic green body is 8 - 12 mm and the thickness is 1.5 - 2.5 mm.

[0018] Preferably, the temperature of the debinding is 550 - 650 °C, the holding time is 1.5 - 2.5 h; the atmosphere of the debinding is air.

[0019] Preferably, the temperature of the sintering is 1500 - 1550 °C, the holding time is 5 - 7 h.

[0020] Preferably, the heating program for heating to the sintering temperature is as follows: heating from room temperature to 1200 °C at a first heating rate, then heating to 1400 °C at a second heating rate, then heating to 1500 °C at a third heating rate, and then heating to the sintering temperature at a fourth heating rate; the first heating rate is 4 - 6 °C / min, the second heating rate is 2 - 4 °C / min, the third heating rate is 1 - 3 °C / min, and the fourth heating rate is 0.5 - 1.5 °C / min; when the sintering temperature is 1500 °C, after heating to 1500 °C, insulation is carried out, and the subsequent heating process is omitted;

[0021] After the sintering, cooling is also included; the cooling program is: first cooling to 800 °C at a rate of 4 - 6 °C / min, and then cooling to room temperature with the furnace.

[0022] The present invention also provides a gadolinium-tantalum co-doped strontium titanate-based giant dielectric ceramic material prepared by the preparation method described in the above solution, and the chemical formula is as shown in Formula I:

[0023] Sr 0.985 Gd 0.015 Ti 1-x Ta x O3 Formula I;

[0024] In Formula I: 0 < x ≤ 0.02.

[0025] Preferably, the dielectric constant of the gadolinium-tantalum co-doped strontium titanate-based giant dielectric ceramic material is 199922 - 320926 at room temperature and a test frequency of 1 kHz, and the dielectric loss range is 0.1119 - 0.2303.

[0026] The present invention provides a preparation method of a gadolinium-tantalum co-doped strontium titanate-based giant dielectric ceramic material, including the following steps: (1) According to the stoichiometric ratio in Formula I (Sr 0.985 Gd 0.015 Ti 1-x Ta x O3, 0 < x ≤ 0.02), strontium carbonate, titanium dioxide, gadolinium oxide and tantalum pentoxide are used for batching, and the obtained raw material powder is subjected to primary ball milling to obtain a mixed powder; the mixed powder is pre-synthesized and then subjected to secondary ball milling to obtain a ceramic powder; (3) The ceramic powder, binder and water are mixed and then successively ground, pressed, aged and crushed to obtain ceramic particles; the ceramic particles are dry-pressed into a ceramic green body; (4) The ceramic green body is debinded and then sintered in a nitrogen atmosphere to obtain the gadolinium-tantalum co-doped strontium titanate-based giant dielectric ceramic material. Gd 3+ The element has a moderate ionic radius The 4f electron shell half-filled characteristic of Gd makes it more stable during the doping process; Ta 5+Element ionic radius is extremely close to Ti 4+ Element ionic radius is extremely close, and only very small lattice distortion occurs during the doping process. Moreover, due to its property of charge compensation as donor doping, it can significantly improve the dielectric properties of the material. Therefore, the present invention uses gadolinium and tantalum for co-doping of strontium titanate materials, and excellent giant dielectric properties can be obtained. In addition, the improvement of dielectric properties by traditional sintering in air atmosphere is limited. The present invention selects sintering in nitrogen atmosphere, so that more oxygen vacancies and other defects are formed in the ceramic material during sintering, and more delocalized electrons are released at the same time. These delocalized electrons will be trapped in various defects inside the material to form a series of defect cluster structures. This structure restricts the long-range displacement of free electrons, enhances the local polarization intensity, and thus improves the dielectric constant and reduces the dielectric loss.

[0027] In summary, the gadolinium-tantalum co-doped strontium titanate-based giant dielectric ceramic material prepared by the present invention has a stable structure. Sintering in nitrogen atmosphere makes the grains finer and the growth more dense. The dual-element doping and atmosphere sintering process makes the types of defect structures inside the material more abundant, and improves the dielectric properties of the strontium titanate-based giant dielectric ceramic material. The results of the examples show that when x = 0.015, at room temperature and a test frequency of 1 kHz, the dielectric constant of the gadolinium-tantalum co-doped strontium titanate-based giant dielectric ceramic material is ~320926, and the dielectric loss is ~0.1119. Description of the drawings

[0028] Figure 1 XRD test results of the ceramic materials prepared in Examples 1 to 5, where (a) is the XRD pattern of the Sr 0.985 Gd 0.015 Ti 1-x Ta x O3 ceramic material sintered at 1550 °C for 6 h in nitrogen atmosphere, and (b) is the partial enlarged view of the diffraction peak of the (110) crystal plane;

[0029] Figure 2 For the Sr 0.985 Gd 0.015 Ti 1-x Ta x surface morphology diagrams of the O3 ceramic materials, where: (a) x = 0, (b) x = 0.005, (c) x = 0.01, (d) x = 0.015, (e) x = 0.02;

[0030] Figure 3 For the Sr 0.985 Gd 0.015 Ti 1-x Ta xDielectric properties of O3 ceramic materials, where (a) shows the variation of dielectric properties with frequency at room temperature; (b) shows the variation of dielectric properties with doping amount at room temperature and 1 kHz.

[0031] Figure 4 For Sr prepared in Example 1 and Example 4 0.985 Gd 0.015 Ti 1-x Ta x Results of electron paramagnetic resonance spectroscopy test of O3 ceramic materials. Detailed implementation manners

[0032] The present invention provides a preparation method of a gadolinium-tantalum co-doped strontium titanate-based giant dielectric ceramic material, comprising the following steps:

[0033] (1) According to the stoichiometric ratio in Formula I, strontium carbonate, titanium dioxide, gadolinium oxide and tantalum pentoxide are used for batching, and the obtained raw material powders are subjected to primary ball milling to obtain mixed powders;

[0034] Sr 0.985 Gd 0.015 Ti 1-x Ta x O3 Formula I;

[0035] In Formula I: 0 < x ≤ 0.02;

[0036] (2) The mixed powders are pre-synthesized and then subjected to secondary ball milling to obtain ceramic powders;

[0037] (3) The ceramic powders, binder and water are mixed and then ground, pressed, aged and crushed in sequence to obtain ceramic particles; the ceramic particles are dry-pressed into a shape to obtain a ceramic green body;

[0038] (4) The ceramic green body is debinded and then sintered in a nitrogen atmosphere to obtain the gadolinium-tantalum co-doped strontium titanate-based giant dielectric ceramic material.

[0039] According to the stoichiometric ratio in Formula I, the present invention uses strontium carbonate, titanium dioxide, gadolinium oxide, and tantalum pentoxide for batching, and the obtained raw material powder is subjected to primary ball milling to obtain a mixed powder. In the present invention, the value range of x in Formula I is preferably 0.005, 0.01, 0.015, or 0.02; the conditions for the primary ball milling preferably include: the milling balls are zirconia balls, the milling medium is deionized water, and the mass ratio of the raw material powder, zirconia balls, and deionized water is preferably 1:5:1.5, the ball milling speed is 300 - 450 rpm, specifically it can be 350 rpm, 400 rpm, or 450 rpm, and the ball milling time is 7 - 9 h, specifically it can be 7 h, 8 h, or 9 h; after the primary ball milling, it is preferably further included to dry the obtained material, the drying temperature is preferably 85 - 100 °C, specifically it can be 90 °C or 100 °C, and the drying time is preferably 20 - 24 h, specifically it can be 22 h or 24 h.

[0040] After obtaining the mixed powder, the present invention pre - synthesizes the mixed powder and then performs secondary ball milling to obtain a ceramic powder. In the present invention, the temperature for the pre - synthesis is preferably 1150 - 1250 °C, specifically it can be 1150 °C, 1200 °C, or 1250 °C, the heat preservation time for the pre - synthesis is preferably 3 - 5 h, specifically it can be 3 h, 3.5 h, 4 h, 4.5 h, or 5 h; the heating program for heating to the temperature for the pre - synthesis is preferably: first heat at a rate of 8 - 12 °C / min (preferably 10 °C / min) to 500 °C, and then heat at a rate of 4 - 6 °C / min (preferably 5 °C / min) to the temperature for the pre - synthesis; the atmosphere for the pre - synthesis is preferably air; after the pre - synthesis is completed, it is preferably cooled down, and the cooling program is preferably: first cool at a rate of 4 - 6 °C / min (preferably 5 °C / min) to 500 °C, and then cool with the furnace to room temperature.

[0041] In the present invention, the milling balls, milling medium, ball milling speed, and time used for the secondary ball milling are all the same as those for the primary ball milling, which will not be elaborated here; during the secondary ball milling, the mass ratio of the powder obtained from the pre - synthesis, zirconia balls, and deionized water is preferably 1:5:1.5; after the secondary ball milling, it is preferably further included to dry the obtained material, the drying temperature is 85 - 100 °C, specifically it can be 90 °C or 100 °C, and the drying time is preferably 20 - 24 h, specifically it can be 22 h or 24 h; before drying, it is preferably further included to first sieve the obtained secondary ball - milled material; the mesh number of the sieve used for sieving is preferably 500 meshes, and the undersize is taken.

[0042] After obtaining the ceramic powder, the present invention mixes the ceramic powder, binder and water, and then successively performs grinding, pressing, aging and pulverization to obtain ceramic particles; the ceramic particles are dry-pressed into a shape to obtain a ceramic green body. In the present invention, the binder is preferably a polyvinyl alcohol solution; the concentration of the polyvinyl alcohol solution is preferably 3-5 wt.%, specifically 4 wt.%; the amount of the binder is preferably 1-2% of the mass of the ceramic powder, specifically 1%, 1.5% or 2%; the amount of water is preferably 0.5-1% of the mass of the ceramic powder, specifically 0.5%, 0.8% or 1%, and the water is preferably deionized water. The present invention has no special requirements for the conditions of the grinding, and those well-known to those skilled in the art can be used; the pressing specifically refers to pressing the ground mixture into a cylindrical shape; the aging time is preferably 24 h, and the aging is preferably carried out at room temperature; the aging is preferably carried out under static conditions; the present invention has no special requirements for the pulverization, and those well-known to those skilled in the art can be used; after pulverization, the obtained pulverized material is preferably sieved, and the material under the sieve is the ceramic particles; the mesh number of the sieve used for sieving is preferably 40 meshes; the dry pressing is preferably carried out under a unidirectional pressure, and the unidirectional pressure for the dry pressing is preferably 10-20 MPa, specifically 10 MPa, 13 MPa, 15 MPa or 20 MPa; the diameter of the ceramic green body is preferably 8-12 mm, specifically 10 mm, and the thickness is preferably 1.5-2.5 mm, specifically 1.5 mm, 2 mm or 2.5 mm.

[0043] After obtaining the ceramic green body, the present invention performs debinding on the ceramic green body and then performs sintering in a nitrogen atmosphere to obtain the gadolinium-tantalum co-doped strontium titanate-based giant dielectric ceramic material. In the present invention, the temperature for debinding is preferably 550-650 °C, specifically 550 °C, 600 °C or 650 °C, the heat preservation time for debinding is preferably 1.5-2.5 h, specifically 1.5 h, 2 h or 2.5 h; the atmosphere for debinding is preferably air; the debinding is preferably carried out in a muffle furnace.

[0044] In the present invention, the sintering temperature is preferably 1500 - 1550 °C, specifically it can be 1500 °C, 1525 °C, 1530 °C, 1540 °C or 1550 °C. The holding time for sintering is preferably 5 - 7 h, specifically it can be 5 h, 5.5 h, 6 h, 6.5 h or 7 h. The heating program for heating to the sintering temperature is preferably: The heating program for heating to the sintering temperature is: heating from room temperature to 1200 °C at a first heating rate, then heating to 1400 °C at a second heating rate, then heating to 1500 °C at a third heating rate, and then heating to the sintering temperature at a fourth heating rate; the first heating rate is preferably 4 - 6 °C / min, specifically it can be 4 °C / min, 5 °C / min or 6 °C / min; the second heating rate is preferably 2 - 4 °C / min, specifically it can be 2 °C / min, 3 °C / min or 4 °C / min; the third heating rate is preferably 1 - 3 °C / min, specifically it can be 1 °C / min, 2 °C / min or 3 °C / min; the fourth heating rate is preferably 0.5 - 1.5 °C / min, specifically it can be 1 °C / min. In the present invention, when the sintering temperature is 1500 °C, after heating to 1500 °C, holding is carried out immediately, and the subsequent heating process can be omitted.

[0045] In the present invention, the sintering atmosphere is a nitrogen atmosphere. The flow rate of the nitrogen atmosphere is preferably 70 - 100 mL / min, specifically it can be 80 mL / min; the sintering is preferably carried out in a tube furnace; in the present invention, preferably, the debound ceramic sample is placed in an alumina crucible, and the alumina crucible is placed in the tube furnace for sintering.

[0046] In the present invention, after sintering, cooling is preferably further included; the cooling program is preferably: first cooling to 800 °C at a rate of 4 - 6 °C / min (specifically it can be 4 °C / min, 5 °C / min or 6 °C / min), and then cooling to room temperature with the furnace.

[0047] The present invention also provides a gadolinium - tantalum co - doped strontium titanate - based giant dielectric ceramic material prepared by the preparation method described in the above solution, and its chemical formula is as shown in Formula I:

[0048] Sr 0.985 Gd 0.015 Ti 1-x Ta x O3 Formula I;

[0049] In Formula I: 0 < x ≤ 0.02. Specifically, x can be 0.005, 0.01, 0.015 or 0.02.

[0050] In the present invention, the gadolinium-tantalum co-doped strontium titanate-based giant dielectric ceramic material has a dielectric constant of 199922 to 320926, preferably 254576 to 320926, and a dielectric loss range of 0.1119 to 0.2303 at room temperature and a test frequency of 1 kHz.

[0051] Next, the technical solutions of the present invention will be clearly and completely described in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0052] Example 1

[0053] Prepare Sr 0.985 Gd 0.015 TiO3 giant dielectric ceramic material. The specific preparation steps are as follows:

[0054] Step 1: Using strontium carbonate, titanium dioxide, and gadolinium oxide as raw materials, formulate according to the chemical formula Sr 0.985 Gd 0.015 TiO3. Perform primary ball milling on the obtained raw material powder. The ball milling balls used for primary ball milling are zirconia balls, and the ball milling medium is deionized water. The mass ratio of the raw material powder, zirconia balls, and deionized water is 1:5:1.5. The ball milling speed is 300 rpm, and the ball milling time is 8 h. Dry the obtained primary ball milled material at 90 °C for 24 h to obtain a mixed powder.

[0055] Step 2: Place the mixed powder obtained in Step 1 in a muffle furnace and perform pre-synthesis in an air atmosphere. The pre-synthesis temperature is 1200 °C, and the time is 4 h. The specific pre-synthesis process is as follows: Heat up to 500 °C at a rate of 10 °C / min, then heat up to 1200 °C at a rate of 5 °C / min, and hold at this temperature for 4 h. After the holding is completed, cool down to 500 °C at a rate of 5 °C / min, and then cool to room temperature with the furnace. Subsequently, perform secondary ball milling (the ball milling conditions are the same as those for primary ball milling), pass through a 500-mesh sieve and dry to prepare Sr 0.985 Gd 0.015 TiO3 ceramic powder.

[0056] Step 3: Mix the ceramic powder prepared in Step 2 with a polyvinyl alcohol solution (concentration: 4 wt.%) and deionized water, and grind them. The amount of the polyvinyl alcohol solution used is 1.5% of the mass of the ceramic powder, and the amount of deionized water used is 1% of the mass of the ceramic powder. Then, press the mixture into a cylindrical shape, let it stand and age for 24 h, crush it, and pass it through a 40-mesh sieve to obtain ceramic particles. Dry-press the ceramic particles under a unidirectional pressure of 15 MPa to obtain a ceramic green body with a diameter of 10 mm and a thickness of 2 mm.

[0057] Step 4: Place the ceramic green body pressed in Step 3 in a muffle furnace for debinding in an air atmosphere. The debinding temperature is 600 °C, and the holding time is 2 h to obtain a Sr 0.985 Gd 0.015 TiO3 ceramic sample.

[0058] Step 5: Place the ceramic sample formed in Step 4 in an alumina crucible, and put the crucible into a tubular furnace for sintering in a nitrogen atmosphere. The nitrogen gas flow rate used for sintering is 80 mL / min. The specific sintering process is as follows: Heat it to 1200 °C at a 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. Subsequently, heat it to 1550 °C at a rate of 1 °C / min and hold it at 1550 °C for 6 h. After the holding is completed, cool it to 800 °C at a rate of 5 °C / min, and then cool it to room temperature with the furnace, thus obtaining a Sr 0.985 Gd 0.015 TiO3 giant dielectric ceramic sheet.

[0059] Polish both sides of the sintered ceramic sheet and coat it with silver electrodes, and place it in a muffle furnace to heat it to 550 °C and hold it for 15 min to burn the electrodes. The dielectric properties are tested using an Agilent 4294A impedance analyzer. The dielectric constant of the ceramic material at room temperature and a test frequency of 1 kHz is ~203620, and the dielectric loss is ~0.0721.

[0060] Example 2

[0061] Prepare Sr 0.985 Gd 0.015 Ti 0.995 Ta 0.005 O3 giant dielectric ceramic material. Use strontium carbonate, titanium dioxide, gadolinium oxide, and tantalum pentoxide as raw materials for batching. The specific preparation steps are the same as those in Example 1, and the subsequent steps are as follows:

[0062] Polish both sides of the sintered ceramic sheet and coat it with silver electrodes, and place it in a muffle furnace to heat it to 550 °C and hold it for 15 min to burn the electrodes. The dielectric properties are tested using an Agilent 4294A impedance analyzer. The dielectric constant of the ceramic material at room temperature and a test frequency of 1 kHz is ~261311, and the dielectric loss is ~0.1468.

[0063] Example 3

[0064] Prepare Sr 0.985 Gd 0.015 Ti 0.99 Ta 0.01 O3 giant dielectric ceramic material, using strontium carbonate, titanium dioxide, gadolinium oxide, and tantalum pentoxide as raw materials for batching. The specific preparation steps are the same as those in Example 1, and the subsequent steps are as follows:

[0065] Polish both sides of the sintered ceramic sheet and coat it with silver electrodes. Place it in a muffle furnace and heat it to 550 °C and keep it warm for 15 min to burn the electrodes. The dielectric properties are tested using an Agilent 4294A impedance analyzer. The dielectric constant of the ceramic material at room temperature and a test frequency of 1 kHz is ~275251, and the dielectric loss is ~0.1146.

[0066] Example 4

[0067] Prepare Sr 0.985 Gd 0.015 Ti 0.985 Ta 0.015 O3 giant dielectric ceramic material, using strontium carbonate, titanium dioxide, gadolinium oxide, and tantalum pentoxide as raw materials for batching. The specific preparation steps are the same as those in Example 1, and the subsequent steps are as follows:

[0068] Polish both sides of the sintered ceramic sheet and coat it with silver electrodes. Place it in a muffle furnace and heat it to 550 °C and keep it warm for 15 min to burn the electrodes. The dielectric properties are tested using an Agilent 4294A impedance analyzer. The dielectric constant of the ceramic material at room temperature and a test frequency of 1 kHz is ~320926, and the dielectric loss is ~0.1119.

[0069] Example 5

[0070] Prepare Sr 0.985 Gd 0.015 Ti 0.98 Ta 0.02 O3 giant dielectric ceramic material, using strontium carbonate, titanium dioxide, gadolinium oxide, and tantalum pentoxide as raw materials for batching. The specific preparation steps are the same as those in Example 1, and the subsequent steps are as follows:

[0071] Polish both sides of the sintered ceramic sheet and coat it with silver electrodes. Place it in a muffle furnace and heat it to 550 °C and keep it warm for 15 min to burn the electrodes. The dielectric properties are tested using an Agilent 4294A impedance analyzer. The dielectric constant of the ceramic material at room temperature and a test frequency of 1 kHz is ~254576, and the dielectric loss is ~0.2303.

[0072] Example 6

[0073] Prepare Sr 0.985 Gd0.015 Ti 0.985 Ta 0.015 O3 giant dielectric ceramic material is prepared with strontium carbonate, titanium dioxide, gadolinium oxide, and tantalum pentoxide as raw materials. The specific preparation steps 1, 2, 3, and 4 are the same as those in Example 1. The subsequent steps are as follows:

[0074] Step 5: The ceramic sample formed in step 4 is placed in an alumina crucible and the crucible is placed in a tube furnace for sintering in a nitrogen atmosphere. The sintering temperature is 1525°C and the holding time is 6h. The heating process is consistent with Example 1. Only after the temperature is raised to 1500°C, the temperature is raised to 1525°C at a rate of 1°C / min. The nitrogen gas flow rate used for sintering is 80mL / min, and Sr 0.985 G 0.015 Ti 0.985 Ta 0.015 O3 giant dielectric ceramic sheet.

[0075] The ceramic sheet obtained by sintering was polished on both sides and coated with silver electrodes, and then placed in a muffle furnace and heated to 550°C for 15 minutes to sinter the electrodes. The dielectric properties were tested using an Agilent 4294A impedance analyzer. The dielectric constant of the ceramic material at room temperature and a test frequency of 1kHz was ~199922, and the dielectric loss was ~0.1174.

[0076] Comparative Example 1

[0077] Preparation of Sr 0.985 G 0.015 Ti 0.985 Ta 0.015 O3 giant dielectric ceramic material, the specific preparation steps 1, 2, 3, and 4 are the same as those in Example 1, and the subsequent steps are as follows:

[0078] Step 5: Place the ceramic sample formed in step 4 in an alumina crucible and place the crucible in a tube furnace for sintering in air atmosphere at a sintering temperature of 1550°C. The heating process is the same as in Example 1 and the holding time is 6 hours to obtain Sr 0.985 G 0.015 Ti 0.985 Ta 0.015 O3 giant dielectric ceramic sheet.

[0079] The ceramic sheet obtained by sintering was polished on both sides and coated with silver electrodes, and then placed in a muffle furnace and heated to 550°C for 15 minutes to sinter the electrodes. The dielectric properties were tested using an Agilent 4294A impedance analyzer. The dielectric constant of the ceramic material at room temperature and a test frequency of 1kHz was ~34028, and the dielectric loss was ~0.3957.

[0080] Comparative Example 2

[0081] Preparation of Sr 0.985 G 0.015Ti 0.985 Ta 0.015 The O3 giant dielectric ceramic material, the specific preparation steps one, two, three, and four are the same as those in Example 1, and the subsequent steps are as follows:

[0082] Step five: Place the ceramic sample formed in step four in an alumina crucible and put the crucible into a tube furnace for sintering in an air atmosphere. The sintering temperature is 1525 °C, and the holding time is 6 h. The heating process is the same as that in Example 1. Only after heating to 1500 °C, heat up to 1525 °C at a rate of 1 °C / min to obtain Sr 0.985 Gd 0.015 Ti 0.985 Ta 0.015 O3 giant dielectric ceramic sheet.

[0083] Polish both sides of the sintered ceramic sheet and coat it with silver electrodes, then place it in a muffle furnace and heat it up to 550 °C for 15 min to burn the electrodes. The dielectric properties are tested using an Agilent 4294A impedance analyzer. At room temperature and a test frequency of 1 kHz, the dielectric constant of the ceramic material is ~30100, and the dielectric loss is ~0.543.

[0084] Performance test:

[0085] 1. Dielectric property test

[0086] The summary of the dielectric properties of the ceramic samples prepared in Examples 1 to 6 and Comparative Examples 1 to 2 is shown in Table 1.

[0087] Table 1 Dielectric property table of the ceramic samples prepared in Examples 1 to 6 and Comparative Examples 1 to 2

[0088]

[0089] 2. XRD test

[0090] Figure 1 The XRD test results of the ceramic materials prepared in Examples 1 to 5 are shown. Among them, (a) is the XRD pattern of the Sr 0.985 Gd 0.015 Ti 1-x Ta x O3 ceramic material sintered at 1550 °C for 6 h in a nitrogen atmosphere, and (b) is the partial enlarged view of the diffraction peak of the (110) crystal plane. As Figure 1 shown in (a) therein, the strontium titanate ceramic samples with different doping amounts in the present invention are all perovskite-type structures, and there are no obvious impurity phases, indicating that Gd 3+ , Ta 5+ ions are successfully doped into the SrTiO3 lattice. According to Figure 1 in (b), combined with the ionic radius sizes of each element it can be known that when Gd3+ When doping, this crystal plane shifts to a high angle, indicating that Gd 3+ ions enter the Sr site, resulting in a decrease in grain size. As the amount of Ta 5+ doping increases, the diffraction peak shifts to a low angle, indicating that Ta 5+ ions enter the Ti site, increasing the lattice parameter.

[0091] 3. Morphology test

[0092] Figure 2 The surface morphology diagrams of the Sr 0.985 Gd 0.015 Ti 1-x Ta x O3 ceramic materials prepared in Examples 1 to 5, where: (a) x = 0, (b) x = 0.005, (c) x = 0.01, (d) x = 0.015, (e) x = 0.02; It can be found through image comparison that as the amount of Ta 5+ is added, the grain size of the ceramic sample increases and becomes more uniform. This is because oxygen vacancies are generated during the doping process, promoting the uniform growth of grains.

[0093] 4. Analysis of the change in dielectric properties of ceramic materials

[0094] Figure 3 The dielectric properties of the Sr 0.985 Gd 0.015 Ti 1-x Ta x O3 ceramic materials prepared in Examples 1 to 5, where (a) is the change in dielectric properties with frequency at room temperature; (b) is the change in dielectric properties with doping amount at room temperature and 1 kHz. According to Figure 3 (a) in it, it can be seen that samples with different doping amounts show similar change curves. At high frequencies, the dielectric constant begins to decrease, and the dielectric loss shows a relaxation peak, presumably related to space charge polarization and interface polarization. Because these two polarization methods are too late to establish at high frequencies, thus affecting the dielectric properties. According to Figure 3 (b) in it, it can be seen that when x = 0.015, the properties of the obtained ceramic material are better, and the obtained dielectric constant is ε r ~320926, and the dielectric loss is tanδ~0.1119. At this time, the element doping and reduction atmosphere sintering make the size and concentration of defects inside the material reach a suitable range, showing better dielectric properties.

[0095] 5. Electron paramagnetic resonance spectroscopy analysis of ceramic materials

[0096] Figure 4 For the Sr 0.985 Gd 0.015 Ti 1-xTa x EPR spectroscopic test results of O3 ceramic materials. According to Figure 4 It can be seen that the ceramic material samples with x = 0 and x = 0.015 both exhibit EPR signals related to paramagnetic oxygen vacancies (V·O) at g = 1.989, indicating that the samples both contain lattice defect structures related to oxygen vacancies. The paramagnetic response peak of the x = 0.015 sample is significantly stronger, indicating that the doping of Ta 5+ significantly increases the oxygen vacancy concentration in the sample.

[0097] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A method for preparing a gadolinium-tantalum co-doped strontium titanate-based giant dielectric ceramic material, characterized in that: The following steps are involved: (1) according to the stoichiometric ratio in formula (I), strontium carbonate, titanium dioxide, gadolinium oxide and tantalum pentoxide are prepared, and the obtained raw material powder is ball-milled once to obtain a mixed powder; Sr 0.985 Gd 0.015 Ti 1-x The x O3 formula I; In formula I: <x≤0.02; (2) pre-synthesizing the mixed powder, and then performing secondary ball milling to obtain ceramic powder; (3) mixing the ceramic powder, the binder and water, and then grinding, pressing, aging and crushing in sequence to obtain ceramic particles; dry-pressing the ceramic particles to obtain a ceramic body; (4) After debinding, the ceramic body is sintered in a nitrogen atmosphere to obtain the gadolinium-tantalum co-doped strontium titanate-based giant dielectric ceramic material.

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: The ball milling balls are zirconia balls, the ball milling medium is deionized water, the ball milling speed is 300-450rpm, and the ball milling time is 7-9h; after the first ball milling and the second ball milling, the obtained material is dried, the drying temperature is 85-100°C, and the time is 20-24h.

3. The preparation method according to claim 1, characterized in that: The presynthesis temperature is 1150-1250°C, the insulation time is 3-5h, and the heating program to the presynthesis temperature is: firstly heating to 500°C at a rate of 8-12°C / min, and then heating to the presynthesis temperature at a rate of 4-6°C / min; the presynthesis atmosphere is air.

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

5. The preparation method according to claim 1, characterized in that: The dry pressing is performed under unidirectional pressure, and the unidirectional pressure of the dry pressing is 10-20 MPa; the diameter of the ceramic body is 8-12 mm, and the thickness is 1.5-2.5 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 1.5-2.5 hours; the debinding atmosphere is air.

7. The preparation method according to claim 1, characterized in that: The sintering temperature is 1500-1550° C., and the heat preservation time is 5-7 hours.

8. The preparation method according to claim 7, characterized in that: The heating procedure for heating to the sintering temperature is: heating from room temperature to 1200°C at a first heating rate, then heating to 1400°C at a second heating rate, then heating to 1500°C at a third heating rate, and then heating to the sintering temperature at a fourth heating rate; the first heating rate is 4-6°C / min, the second heating rate is 2-4°C / min, the third heating rate is 1-3°C / min, and the fourth heating rate is 0.5-1.5°C / min; when the sintering temperature is 1500°C, heating to 1500°C is followed by heat preservation, and the subsequent heating process is omitted; The sintering process also includes cooling down; the cooling process is as follows: firstly cooling down to 800°C at a rate of 4-6°C / min, and then cooling down to room temperature along with the furnace.

9. The gadolinium-tantalum co-doped strontium titanate-based giant dielectric ceramic material prepared by the preparation method according to any one of claims 1 to 8, characterized in that: The chemical formula is shown in Formula I: Sr 0.985 Gd 0.015 Ti 1-x The x O3 formula I; In formula I: <x≤0.02。 10. The gadolinium-tantalum co-doped strontium titanate-based giant dielectric ceramic material according to claim 9, characterized in that: The gadolinium-tantalum co-doped strontium titanate-based giant dielectric ceramic material has a dielectric constant of 199922 to 320926 at room temperature and a test frequency of 1 kHz, and a dielectric loss range of 0.1119 to 0.2303.

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