Preparation method and application of sr / co co-doped ccto giant dielectric ceramics

Abstract

The application discloses a preparation method and application of Sr / Co co-doped CCTO giant dielectric ceramic and belongs to the technical field of ceramic preparation. 2+ Ca 2+ TiO3 and Co2TiO4 phases are formed at the grain boundaries, so that the grain boundary resistivity and dielectric loss are reduced, and the effect of effectively regulating the dielectric properties of the ceramic is achieved. 2+ Ca 2+ TiO3 and Co2TiO4 phases are formed at the grain boundaries, so that the grain boundary resistivity and dielectric loss are reduced, and the effect of effectively regulating the dielectric properties of the ceramic is achieved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of ceramic preparation, and particularly relates to a preparation method of Sr / Co co-doped CCTO giant dielectric ceramic and application thereof. BACKGROUND

[0002] With the continuous development of electronic science and technology, people's demand for energy is increasing, and energy problems have attracted widespread attention. We urgently need renewable energy to cope with the increase in energy consumption, and the development of efficient and low-cost energy storage devices is also a key problem to be solved. At present, common storage devices mainly include capacitors, batteries and generators. Among them, the dielectric capacitor as an electrochemical energy storage device has broad research prospects. Among them, the giant dielectric material in the dielectric material has broad application prospects in the microelectronic field, and plays an important role in the miniaturization and high speed of devices. However, it is still a difficult challenge to obtain high dielectric constant, low dielectric loss and good temperature stability at the same time.

[0003] At present, among the common giant dielectric materials, BaTiO3-based ceramics belong to ferroelectric materials, which have two obvious shortcomings: first, the ferroelectric-paraelectric phase transition occurs at the Curie temperature, which makes the dielectric constant change obviously with temperature, and the stability is poor; second, many ferroelectric dielectric materials contain lead, which is harmful to human body. SrTiO3-based ceramics have perovskite crystal structure and wide band gap (~ 3.2eV), and are excellent dielectric materials with moderate dielectric constant and low loss, which cannot usually meet the requirements of wider temperature range. TiO2-based ceramics have rutile structure, and the dielectric loss increases sharply with the increase of frequency, and the grain size is large, which is difficult to realize miniaturization. After modification, it has large dielectric constant and good dielectric thermal stability.

[0004] CCTO as a mainstream giant dielectric ceramic material has been concerned by researchers since Subramanian et al. reported that CCTO material has high dielectric constant. It is a cubic structure chalcogenide compound with lattice constant Ti atoms are located at the center of the oxygen octahedron, and the 8 corners of the octahedron are respectively occupied by Ca 2+ and Cu 2+The resulting TiO6 octahedra are connected to six neighboring different CuO4, making the TiO6 octahedral structure tilted. This special structure of CCTO is the main reason for its excellent dielectric constant, temperature stability, frequency stability and nonlinear electrical properties, which makes it can be used as high energy density storage medium. Although CCTO has many advantages, but it also has some shortcomings limit its use, such as high dielectric loss, modern electronic device applications urgently need to reduce dielectric loss while improving the dielectric constant, therefore, how to keep high dielectric constant and reduce dielectric loss of CCTO material is a problem to be solved.

[0005] Current researchers improve the performance of CCTO in many ways, such as: single doping, co-doping, multiple composite, shell structure, etc. Among them, doping is a very effective modification method. Chun-Hong Mu (C.-H. Mu, P. Liu, Y. He, J.-P. Zhou, H.-W. Zhang, An effective method to decrease dielectric loss of CaCu3Ti4O 12 ceramics, J. Alloys Compd. 471 (2009) 137e141.) et al. doped Sr 2+ in CCTO ceramics, their results show that the change of grain boundary structure leads to the decrease of dielectric loss, but the dielectric constant is reduced to 10 4 Below. Z. Kaf et al. (Z. Kafi, A. Kompany, H. Arabi, A. Khorsand Zak, The effect of cobalt-doping on microstructure and dielectric properties of CaCu3Ti4O 12 ceramics, J. Alloy. Compd. 727 (2017) 168-176.) believe that the dielectric loss (tanδ) can be reduced by controlling the structure and chemical properties of the grain boundary region in CCTO ceramics. By reducing the CuO phase with semiconductor behavior, and by replacing the Cu 2+ site in CCTO ceramics with Co 2+Instead, CaTiO3 and Co2TiO4 phases with good dielectric insulation performance are formed in the grain boundary to reduce the leakage current caused by the reduction of the grain boundary conductivity, thereby reducing the dielectric loss and the increase of the dielectric constant in the CCTO ceramic. Compared with single doping, co-doping is an effective method to improve the performance, while the research on co-doping is less. In view of the above problems, the preparation method and application of Sr / Co co-doped CCTO giant dielectric ceramic are provided. SUMMARY

[0006] The purpose of the present application is to provide a preparation method and application of Sr / Co co-doped CCTO giant dielectric ceramic, which solves the problem of simultaneous increase or decrease of CCTO dielectric constant and dielectric loss in the prior art single-doped CCTO modification.

[0007] The prior art single-doped CCTO modification has the problem of simultaneous increase or decrease of CCTO dielectric constant and dielectric loss. In view of the above problems, the preparation method and application of Sr / Co co-doped CCTO giant dielectric ceramic are provided. In the present application, Sr 2+ ions are used to substitute and dope Ca 2+ sites, which can effectively increase the grain boundary resistance and Schottky barrier height, and enhance the dielectric relaxation characteristics. Co 2+ ions are used to substitute and dope Cu 2+ sites, which can form CaTiO3 and Co2TiO4 phases at the grain boundary, realize the reduction of Cu-rich phase, thereby reducing the grain boundary resistivity and dielectric loss, and achieving the effect of effectively regulating the dielectric properties of the ceramic.

[0008] The present application is realized in that the preparation method of Sr / Co co-doped CCTO giant dielectric ceramic comprises:

[0009] S10, taking powder raw materials for preparing co-doped CCTO giant dielectric ceramic, the powder raw materials comprising CaCO3 powder, CuO powder, TiO2 powder, SrCO3 powder and CoO powder, the CaCO3 powder, CuO powder, TiO2 powder, SrCO3 powder and CoO powder being dosed according to the stoichiometric ratio, then alcohol being added, the powder raw materials being subjected to primary ball milling treatment, the ball milling treatment being completed, then being dried to obtain a precursor powder;

[0010] S20, taking the precursor powder, pre-sintering the precursor powder to obtain a pre-sintered powder, which is ready for use;

[0011] S30, obtaining the pre-sintered powder, performing secondary ball milling treatment on the pre-sintered powder, and performing drying treatment on the pre-sintered powder after the secondary ball milling treatment to obtain ceramic powder, for standby use;

[0012] S40, taking the ceramic powder, performing tabletting and molding on the ceramic powder to obtain a green body, for standby use;

[0013] S50, taking the green body, and sintering the green body to obtain a Sr / Co co-doped CCTO giant dielectric ceramic material.

[0014] Preferably, in step S10, the particle size of the powder raw material is less than 250 nm, and when performing the primary ball milling treatment on the powder raw material, the primary ball milling uses zirconium oxide balls as milling balls and anhydrous ethanol as a ball milling medium, the mass ratio of the powder raw material to the zirconium oxide balls is 1:2.5-3, the mass ratio of the anhydrous ethanol to the powder raw material is 1:1.1-1.3, the primary ball milling rotation speed is 450-500 r / min, and the primary ball milling time is 12-24 h.

[0015] Preferably, in step S20, when performing the pre-sintering on the precursor powder, the pre-sintering temperature is 900-1000℃, the temperature rising rate from room temperature to the pre-sintering temperature is 3-5℃ / min, and the pre-sintering time is 8-10 h.

[0016] Preferably, in step S30, the rotation speed of the secondary ball milling is 450-550 r / min, and the secondary ball milling time is 12-20 h.

[0017] Preferably, in step S40, when performing the tabletting and molding on the ceramic powder, the tabletting and molding mode adopts the first molding mode or the second molding mode.

[0018] Preferably, the first molding mode comprises:

[0019] Taking the ceramic powder, and sequentially performing pre-pressing and molding and cold isostatic pressing on the ceramic powder, wherein the temperature of the cold isostatic pressing is room temperature, the pressure of the cold isostatic pressing is 200-250 MPa, and the time of the cold isostatic pressing is 2-5 min.

[0020] Preferably, the second molding mode comprises:

[0021] Taking the ceramic powder, mixing the ceramic powder with a binder, and performing granulation to obtain powder particles;

[0022] Performing press molding on the obtained powder particles or sequentially performing pre-pressing and molding and cold isostatic pressing on the obtained powder particles;

[0023] When the second molding mode is adopted, the method further comprises, before sintering, performing degassing on the obtained green body, wherein the temperature of the degassing is 500-550℃, and the holding time is 6-9 h.

[0024] Preferably, in step S50, the green body sintering temperature is 1050-1100 DEG C, and the holding time of the sintering is 8-10h.

[0025] Preferably, the Sr / Co co-doped CCTO giant dielectric ceramic material has a chemical composition of Ca 1-x Sr x Cu 3- y Co y Ti4O 12 .

[0026] The application also provides an application of the preparation method of the Sr / Co co-doped CCTO giant dielectric ceramic in a dielectric capacitor.

[0027] Compared with the prior art, the application has the following beneficial effects:

[0028] In the application, Sr 2+ ions are used to substitute and dope Ca 2+ ion sites, which can effectively increase the grain boundary resistance and the Schottky barrier height, and can enhance the dielectric relaxation characteristics. 2+ By substituting and doping Co 2+ ions to Cu 4 ion sites, CaTiO3 and Co2TiO4 phases are formed at the grain boundaries, the reduction of the Cu-rich phase is realized, the grain boundary resistivity and the dielectric loss are reduced, and the dielectric properties of the ceramic are effectively controlled. 4 The dielectric constant of the CSCCTO giant dielectric ceramic material provided by the application can reach 10 4 The dielectric loss can be as low as 0.04. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 The SEM micro-morphology diagrams of the Sr / Co co-doped CCTO giant dielectric ceramic samples prepared in Examples 1-4 of the application are shown.

[0030] Figure 2 The XRD diffraction patterns of the Sr / Co co-doped CCTO giant dielectric ceramic samples prepared in Examples 1-4 of the application are shown.

[0031] Figure 3 The curves of the relative dielectric constant and the dielectric loss of the Sr / Co co-doped CCTO giant dielectric ceramic samples prepared in Examples 1-4 of the application with the change of frequency are shown.

[0032] Figure 4 The diagrams of the dielectric constant of the Sr / Co co-doped CCTO giant dielectric ceramic samples prepared in Examples 1-4 of the application with the change of temperature at a specific frequency are shown.

[0033] Figure 5 Fig. 3 shows a diagram of the change of the dielectric loss of the Sr / Co co-doped CCTO giant dielectric ceramic sample prepared in Embodiment 1-4 with temperature at a specific frequency. DETAILED DESCRIPTION

[0034] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs; the terminology used in the description herein is for describing particular embodiments only and is not intended to be limiting of the application; the description and claims herein and the above description of drawings herein utilize terms such as "including" and "having" and variations thereof that are intended to be broad enough to encompass the presence of zero or more of the specified elements or steps without limitation. The terms "first," "second," and the like, as used herein do not have any specific sequential or chronological significance, but are used only to distinguish one element from another.

[0035] The prior art has the problem that the dielectric constant and dielectric loss of CCTO single-doped modification increase or decrease simultaneously, and the present application provides a preparation method of Sr / Co co-doped CCTO giant dielectric ceramic and application thereof, in which Sr 2+ Ca 2+ Substitution doping of Ca 2+ Cu 2+ Substitution doping of Ca

[0036] The embodiment of the present application provides a preparation method of Sr / Co co-doped CCTO giant dielectric ceramic, and the preparation method of the Sr / Co co-doped CCTO giant dielectric ceramic specifically comprises the following steps.

[0037] S10, taking powder raw materials for preparing co-doped CCTO giant dielectric ceramic, the powder raw materials comprising CaCO3 powder, CuO powder, TiO2 powder, SrCO3 powder and CoO powder, after the CaCO3 powder, the CuO powder, the TiO2 powder, the SrCO3 powder and the CoO powder are prepared according to a stoichiometric ratio, alcohol is added, and the powder raw materials are subjected to one-time ball milling treatment, and after the ball milling treatment is completed, the powder raw materials are dried to obtain precursor powder;

[0038] It should be noted that in step S10, the particle size of the powder raw material is less than 250 nm. This invention does not have special requirements regarding the source of the powders; commercially available products familiar to those skilled in the art can be used. During the primary ball milling of the powder raw material, zirconia balls are used as the grinding balls, and anhydrous ethanol is used as the grinding medium. The mass ratio of powder raw material to zirconia balls is 1:2.5-3, and the mass ratio of anhydrous ethanol to powder raw material is 1:1.1-1.3. The primary ball milling speed is 450-500 r / min, more preferably 550 r / min, and the primary ball milling time is 12-24 h, more preferably 15-20 h. In this invention, the primary ball milling is preferably carried out in a planetary ball mill, and the planetary ball mill preferably uses a nylon grinding jar. This invention does not have special limitations on the model of the planetary ball mill; instruments and equipment familiar to those skilled in the art can be used.

[0039] Simultaneously, this invention uses a single ball milling process to uniformly mix all components in the powder raw material. After the single ball milling, it is preferable to separate the grinding balls from the resulting ball milling material, and then sequentially perform drying, grinding, and sieving to obtain a uniform precursor powder. This invention does not have specific limitations on the manual grinding operation; any operation familiar to those skilled in the art can be used. Preferably, the ball milling material after separating the grinding balls is poured into an evaporating dish, and then the evaporating dish is placed in a drying oven for drying. The drying temperature is preferably 80-90℃, and the drying time is preferably 12-24 hours. The sieving is preferably performed through an 80-mesh sieve, and the undersize material is collected to obtain the precursor powder.

[0040] S20, take the precursor powder, pre-calcine the precursor powder to obtain pre-calcine powder, and set aside for later use;

[0041] It should be noted that in step S20, when the precursor powder is pre-calcined, the pre-calcination temperature is 900-1000℃, the heating rate from room temperature to the pre-calcination temperature is 3-5℃ / min, and the pre-calcination time is 8-10h.

[0042] After obtaining the precursor powder, the present invention pre-calcines the precursor powder to obtain pre-calcined powder. Preferably, the precursor powder is placed in an alumina crucible, the crucible is covered, and then pre-calcined. The pre-calcination temperature is preferably 950-1000℃; the heating rate from room temperature to the pre-calcination temperature is preferably 3-4℃ / min; and the pre-calcination holding time is more preferably 8-10 hours. Through pre-calcination, the various oxide components undergo preliminary chemical reactions, reducing the shrinkage rate of the product during sintering. Controlling the pre-calcination temperature has a significant impact on controlling the shrinkage rate, powder activity, and determining the final sintering temperature. After pre-calcination, the pre-calcined product is preferably naturally cooled to room temperature and then ground to obtain pre-calcined powder.

[0043] S30, obtaining the pre-sintered powder, performing secondary ball milling on the pre-sintered powder, and drying the pre-sintered powder after the secondary ball milling to obtain the ceramic powder, for standby use;

[0044] In step S30, the rotation speed of the secondary ball milling is 450-550 r / min, and the time of the secondary ball milling is 12-20 h.

[0045] It should be noted that after obtaining the pre-sintered powder, the pre-sintered powder is subjected to secondary ball milling, and the obtained ceramic powder is formed to obtain a green sample. In the present application, the ball mill, grinding balls, ball milling medium and their amount used in the secondary ball milling are preferably the same as those used in the primary ball milling, which will not be described here; the rotation speed of the secondary ball milling is preferably 500 r / min, and the time of the secondary ball milling is preferably 12-13 h. The pre-sintered powder may be agglomerated, and the ceramic powder is ground to a certain particle size (particle size 0.5-0.8 μm) by the secondary ball milling, so that the particle size distribution of the powder is relatively narrow, which is beneficial to forming. In the present application, the time of the secondary ball milling has a great influence on the material performance. If the ball milling time is too short, the particle size of the powder is too large, and if the ball milling time is too long, not only the particle size of the powder is not affected, but also impurities are brought in, thereby reducing the performance of the material. After the secondary ball milling, the obtained ball mill is preferably dried, ground and sieved in sequence to obtain the ceramic powder. The ball mill is preferably poured into an evaporation dish, and the evaporation dish is placed in a drying oven for drying. The temperature of the drying is preferably 80℃, and the time is preferably 24 h; the sieving is preferably sieved through a 100-mesh sieve, and the undersize is taken.

[0046] S40, taking the ceramic powder, and performing tablet compression molding on the ceramic powder to obtain a green compact, for standby use;

[0047] In the embodiment of the present application, when the ceramic powder is subjected to tablet compression molding in step S40, the tablet compression molding mode adopts the first molding mode or the second molding mode.

[0048] The first molding mode comprises:

[0049] The ceramic powder is taken, and the ceramic powder is subjected to pre-pressing molding and cold isostatic pressing in sequence. The temperature of the cold isostatic pressing is room temperature, the pressure of the cold isostatic pressing is 200-250 MPa, and the time of the cold isostatic pressing is 2-5 min.

[0050] Specifically, the first forming method preferably comprises: sequentially pre-pressing (denoted as first pre-pressing, which can also be referred to as tabletting) and cold isostatic pressing (denoted as first cold isostatic pressing) of the ceramic powder to obtain a green body. In the present application, the pressure of the first pre-pressing is preferably 100-180 MPa, more preferably 100-150 MPa, and the pressure holding time is preferably 1 min; the ceramic powder is preferably placed in a stainless steel mold and subjected to first pre-pressing under the pressure condition in a manual tablet press in the present application, and in the embodiments of the present application, the ceramic powder is specifically placed in a cylindrical stainless steel mold and pressed into a cylindrical sample. The pressure of the first cold isostatic pressing is preferably 200-250 MPa, more preferably 230-250 MPa, and the pressure holding time is preferably 2 min.

[0051] The second forming method comprises:

[0052] The ceramic powder is taken, mixed with a binder, and then granulated to obtain powder particles;

[0053] The obtained powder particles are subjected to compression molding or the obtained powder particles are sequentially subjected to pre-pressing and cold isostatic pressing;

[0054] The second forming method preferably comprises: mixing the ceramic powder with a binder, granulating the obtained powder particles, and then compression molding the obtained powder particles to obtain a green body. In the present application, the binder is preferably a polyvinyl alcohol (PVA) solution, and the mass fraction of the polyvinyl alcohol solution is preferably 5-10%; the mass ratio of the ceramic powder to the polyvinyl alcohol solution is preferably 5:1. The present application does not have special requirements for the specific operation method of the granulation, and a granulation method known to those skilled in the art can be used. In the present application, the pressure of the compression molding is preferably 200-230 MPa, and the pressure holding time is preferably 1 min; the present application preferably passes the obtained powder particles after granulation through a 60-mesh and a 100-mesh sieve, and then takes uniform particles on the 100-mesh sieve for compression molding. Alternatively, the second forming method preferably comprises: sequentially pre-pressing (denoted as second pre-pressing) and cold isostatic pressing (denoted as second cold isostatic pressing) of the above-mentioned obtained powder particles to obtain a green body. In the present application, the pressure of the second pre-pressing is preferably 100-180 MPa, more preferably 160-180 MPa, and the pressure holding time is preferably 1 min; the pressure of the second cold isostatic pressing is preferably 200-250 MPa, more preferably 200-220 MPa, and the pressure holding time is preferably 2 min.

[0055] When the second forming method is used, the obtained green body is also subjected to degreasing before sintering, and the temperature of the degreasing is 500-550℃, and the holding time is 6-9h.

[0056] In the present application, when the forming adopts the second forming mode, the obtained green body is preferably subjected to degreasing before sintering. In the present application, the temperature of the degreasing is preferably 500-550℃, more preferably 500-520℃, and the holding time is preferably 6-9h, more preferably 8-9h; by the degreasing, the binder in the green body is fully decomposed, volatilized or removed, so as to prevent deformation or cracking of the green body during sintering, thereby facilitating obtaining a high-quality ceramic sintered sample.

[0057] S50, taking the green body, and sintering the green body to obtain the Sr / Co co-doped CCTO giant dielectric ceramic material.

[0058] The CCTO has a chemical formula of CaCu3Ti4O 12 In the present embodiment, in step S50, the sintering temperature of the green body is 1050-1100℃, and the holding time of the sintering is 8-10h.

[0059] After obtaining the green body, the present application sintering the green body to obtain the CSCCTO giant dielectric ceramic material. In the present application, the heating rate for heating to the sintering temperature is preferably 3-5℃ / min; the holding time of the sintering is more preferably 9-10h; and the sintering is preferably carried out in an air atmosphere. In the present application, the sintering is a process of solid-phase reaction. In the present application, the degreasing and the sintering are both preferably carried out in a muffle furnace; and the sintering is preferably naturally cooled to room temperature after the sintering.

[0060] It should be noted that the Sr / Co co-doped CCTO giant dielectric ceramic material prepared in the present embodiment has a chemical composition of Ca 1-x Sr x Cu 3-y Co y Ti4O 12 (x is 0-0.1, and y is 0-0.1).

[0061] In the present application, the Sr 2+ ions are used to substitute and dope the Ca 2+ ion sites, which can effectively increase the grain boundary resistance and the Schottky barrier height, and can enhance the dielectric relaxation characteristics; and the Co 2+ ions are used to substitute and dope the Cu 2+ ion sites, which can form CaTiO3 and Co2TiO4 phases at the grain boundaries, realize reduction of the Cu-rich phase, thereby reducing the grain boundary resistivity and the dielectric loss, and achieving the effect of effectively regulating the dielectric properties of the ceramic; the dielectric constant of the CSCCTO giant dielectric ceramic material provided by the present application can reach 10 4 The dielectric loss can be as low as 0.04.

[0062] Example 1

[0063] In the embodiment, a preparation method of Sr / Co co-doped CCTO giant dielectric ceramic is provided, and the preparation method of the Sr / Co co-doped CCTO giant dielectric ceramic specifically comprises the following steps.

[0064] S101, weighing and mixing: CaCO3 powder, CuO powder and TiO2 powder (the particle size of the above-mentioned powders is less than 250 nm) are weighed by stoichiometry as raw materials for batching; the mixed powder and zirconia balls are loaded into a ball mill tank in a mass ratio of 1:2.5, and a certain amount of anhydrous ethanol (the mass ratio of anhydrous ethanol to mixed powder is 1:1.2) is added, and wet ball milling is carried out in a planetary ball mill at a rotating speed of 550 r / min for 18 h; after drying, grinding and sieving (through an 80-mesh sieve, and the undersize is taken), a uniform precursor powder is obtained;

[0065] S102, pre-sintering and grinding: the precursor powder is loaded into a zirconia crucible, and pre-sintering is carried out in a high-temperature muffle furnace at 1000℃ (the heating rate is 3℃ / min) for 10 h, and the furnace is opened after natural cooling to room temperature, and the pre-sintered powder is obtained after regrinding;

[0066] S103, forming: the pre-sintered powder is subjected to secondary ball milling (zirconia balls and anhydrous ethanol are added, the rotating speed is 500 r / min, and the ball milling time is 12 h), drying and grinding, then a polyvinyl alcohol (PVA) solution with a mass fraction of 5wt.% (the mass ratio of powder to PVA solution is 5:1) is added to the ground powder as a binder for granulation, and after passing through 60-mesh and 100-mesh sieves, the uniform powder particles on the 100-mesh sieve are taken and placed into a stainless steel mold with a diameter of 10 mm, pre-pressed, and a round disc-shaped sample is prepared, which is then placed into a cold isostatic pressing machine, and a cylindrical green sample is prepared under a pressure of 200 MPa for 2 min.

[0067] S104, degassing and sintering: the cylindrical green sample is loaded into a zirconia crucible and placed into a high-temperature muffle furnace, degassing is carried out at 500℃ for 9 h, and then sintering is carried out at 1090℃ in an air atmosphere for 8 h, and the sample is obtained after the furnace is cooled to room temperature.

[0068] Example 2

[0069] In the embodiment of the application, the raw materials in step S101 of Example 1 are changed to CaCO3 powder, CuO powder, TiO2 powder and SrCO3 powder, and the remaining steps of the preparation method of the Sr / Co co-doped CCTO giant dielectric ceramic are the same as those of Example 1.

[0070] Example 3

[0071] In the embodiment of the present application, the raw materials in step S101 of embodiment 1 are replaced by CaCO3 powder, CuO powder, TiO2 powder, CoO powder, and the remaining steps of the preparation method of Sr / Co co-doped CCTO giant dielectric ceramic are the same as those of embodiment 1.

[0072] Embodiment 4

[0073] In the embodiment of the present application, the raw materials in step S101 of embodiment 1 are replaced by CaCO3 powder, CuO powder, TiO2 powder, CoO powder, and the remaining steps of the preparation method of Sr / Co co-doped CCTO giant dielectric ceramic are the same as those of embodiment 1.

[0074] Performance test:

[0075] The Sr / Co co-doped CCTO giant dielectric ceramic samples prepared in embodiments 1-4 are taken for SEM micro-morphology, XRD diffraction pattern, and electrical performance tests. Among them, the SEM micro-morphology is tested by a scanning electron microscope, and the XRD diffraction pattern is tested by an X-ray diffractometer, and the test results are shown in Figure 1 and Figure 2 .

[0076] Among them, Figure 1 shows the SEM micro-morphology of the Sr / Co co-doped CCTO giant dielectric ceramic samples prepared in embodiments 1-4, Figure 1 , wherein (a)-(d) correspond to the Sr / Co co-doped CCTO giant dielectric ceramic samples prepared in embodiments 1-4, respectively. Figure 1 It can be seen that the Sr / Co co-doped CCTO giant dielectric ceramic sample prepared in embodiment 4 has smaller crystal grains than those of other embodiments, which indicates that Sr / Co co-doping reduces the grain size of CCTO, the number of grain boundaries increases significantly, the electrostatic potential barrier increases, the dielectric loss decreases, and the microstructure is relatively dense, and the surface has no obvious micropore defects.

[0077] Figure 2 shows the XRD diffraction pattern of the Sr / Co co-doped CCTO giant dielectric ceramic samples prepared in embodiments 1-4. From Figure 2 , it can be seen that all samples show a similar perovskite structure as CaCu3Ti4O 12 ceramic (CCTO), which indicates that the CSCCTO ceramic sample is successfully prepared.

[0078] The Sr / Co co-doped CCTO giant dielectric ceramic samples prepared in Examples 1-4 of the present application were polished, polished, silver electrodes were made (the thickness and diameter of the ceramic material sample needed to be measured), and then the electrical performance was tested, wherein the silver electrodes were made by coating or printing silver paste onto the upper and lower surfaces of the ceramic material sample, and then placed in a muffle furnace for silver firing at 600°C for 30 min, and the test results are shown in Table 1. Figures 3-5 , Table 1.

[0079] Among them, Figure 3 shows the relative dielectric constant (ε') and dielectric loss (tan δ) of the Sr / Co co-doped CCTO giant dielectric ceramic samples prepared in Examples 1-4 of the present application as a function of frequency, Figure 3 (a) is the dielectric constant of the sample as a function of frequency, and (b) is the dielectric loss of the sample as a function of frequency. From Figure 3 It can be seen that all the Sr / Co co-doped CCTO giant dielectric ceramic samples of the examples exhibit giant dielectric constant response (10 4 above), and good stability in the entire frequency test range, in addition, the dielectric loss of the Sr / Co co-doped CCTO giant dielectric ceramic sample basically presents a trend of first decreasing and then increasing with the increase of the test frequency, at high frequency, the significant relaxation peak in the dielectric loss spectrum is closely related to the change of dielectric constant observed in the dielectric constant and frequency relationship graph. And in the range of 10 2 -10 3 Hz, the dielectric loss of the Sr / Co co-doped CCTO giant dielectric ceramic sample of Example 4 is relatively low. This phenomenon shows that the Sr / Co co-doped CCTO giant dielectric ceramic can effectively reduce the dielectric loss at low frequency.

[0080] Figure 4 shows the dielectric constant of the Sr / Co co-doped CCTO giant dielectric ceramic samples prepared in Examples 1-4 of the present application as a function of temperature at a specific frequency, from Figure 4 It can be seen that all the Sr / Co co-doped CCTO giant dielectric ceramic samples of the examples exhibit giant dielectric constant (10 4 above) in the temperature range of 30°C-210°C, and excellent stability in the temperature range of 30°C-210°C. The dielectric constant of all the ceramics increases with the increase of the test temperature, which is related to the synergistic effect of electrode polarization and carrier migration. And it can be observed that the dielectric constant of all the samples presents a downward trend with the increase of the frequency, indicating that the thermal activation process such as interface polarization starts to work in this temperature range. The dielectric constant is relatively stable at low temperature, the change amplitude at low frequency is obviously increased at high temperature, and it remains stable at high frequency.

[0081] Figure 5 The figure shows the change of the dielectric loss of the Sr / Co co-doped CCTO giant dielectric ceramic samples prepared in the embodiments 1-4 with temperature at a specific frequency, which is shown in the figure. Figure 5 It can be seen that in the temperature range of 30-210 DEG C, with the increase of temperature, the loss shows an upward trend in the frequency range of 100 Hz-100 kHz. At lower frequencies, the dielectric loss of all samples increases significantly with the increase of test temperature, which can be explained by the DC conduction mechanism related to the grain. And the rising becomes more and more flat with the increase of frequency, indicating that in this temperature range, the thermal activation process such as interface polarization begins to work, and the loss is stable at low temperature, and the change amplitude at low frequency increases obviously at high temperature, and remains stable at higher frequency, which is closely related to the change trend of dielectric constant. And Table 1 shows the dielectric loss value of the frequency band of the Sr / Co co-doped CCTO giant dielectric ceramic samples prepared in the embodiments 1-4.

[0082] Table 1

[0083]

[0084] From Table 1, Figures 3-5 It can be seen that the Sr / Co co-doped CCTO giant dielectric ceramic provided by the application has giant dielectric constant, low dielectric loss, excellent temperature stability and excellent comprehensive performance, and is a high-performance giant dielectric ceramic material.

[0085] In summary, the application provides a preparation method and application of Sr / Co co-doped CCTO giant dielectric ceramic. In the application, Sr 2+ ions are used to substitute and dope Ca 2+ ion sites, which can effectively increase the grain boundary resistance and Schottky barrier height, and can enhance the dielectric relaxation characteristics. Co 2+ ions are used to substitute and dope Cu 2+ ion sites, which can form CaTiO3 and Co2TiO4 phases at the grain boundary, realize the reduction of Cu-rich phase, and thus reduce the grain boundary resistivity and dielectric loss, so as to effectively control the dielectric properties of the ceramic. The dielectric constant of the CSCCTO giant dielectric ceramic material provided by the application can reach 10 4 Above, the dielectric loss can be as low as 0.04.

[0086] It should be noted that, for the foregoing embodiments, for the sake of simple description, they are all expressed as a series of action combinations, but those skilled in the art should know that the present application is not limited by the order of the described actions, because according to the present application, certain steps can be performed in other orders or simultaneously. Secondly, those skilled in the art should know that the embodiments described in the specification are all preferred embodiments, and the actions and modules involved are not necessarily necessary for the present application.

[0087] The above embodiments are only used to illustrate the technical solutions of the present application, and not to limit the protection scope of the application. Obviously, the described embodiments are only some of the embodiments of the present application, not all. Based on these embodiments, all other embodiments obtained by those of ordinary skill in the art without creative labor belong to the scope of protection of the present application. Although the present application has been described in detail with reference to the above embodiments, those of ordinary skill in the art can still combine, add or delete or make other adjustments to the features of the embodiments of the present application according to the circumstances without conflict and without creative labor, so as to obtain different other technical solutions which do not deviate from the concept of the present application in essence. These technical solutions also belong to the scope of protection of the present application.

Claims

1. A method for preparing Sr / Co co-doped CCTO giant dielectric ceramics, characterized in that, The method comprises: S10, taking powder raw materials for preparing co-doped CCTO giant dielectric ceramic, the powder raw materials comprising CaCO3 powder, CuO powder, TiO2 powder, SrCO3 powder and CoO powder, after the CaCO3 powder, CuO powder, TiO2 powder, SrCO3 powder and CoO powder are dosed according to stoichiometric ratios, alcohol is added, and the powder raw materials are subjected to first ball milling treatment, and then dried to obtain precursor powder; In step S10, the particle size of the powder raw materials is less than 250 nm, and when the powder raw materials are subjected to first ball milling treatment, zirconium oxide balls are used as milling balls, and anhydrous ethanol is used as a ball milling medium, the mass ratio of the powder raw materials to the zirconium oxide balls is 1:2.5-3, the mass ratio of the anhydrous ethanol to the powder raw materials is 1:1.1-1.3, the first ball milling speed is 450-500 r / min, and the first ball milling time is 12-24 h; S20, taking the precursor powder, pre-sintering the precursor powder to obtain pre-sintered powder, and reserving the pre-sintered powder; S30, taking the pre-sintered powder, subjecting the pre-sintered powder to second ball milling treatment, and drying the pre-sintered powder after the second ball milling treatment to obtain ceramic powder, and reserving the ceramic powder; S40, taking the ceramic powder, tabletting the ceramic powder to obtain a green body, and reserving the green body; In step S40, when the ceramic powder is tabletted, a first forming mode or a second forming mode is used, wherein the second forming mode comprises: taking the ceramic powder, mixing the ceramic powder with a binder, and granulating to obtain powder particles; the obtained powder particles are subjected to compression molding or the obtained powder particles are sequentially subjected to pre-compression molding and cold isostatic pressing; when the second forming mode is used, the obtained green body is subjected to degreasing before sintering, the degreasing temperature is 500-550 DEG C, and the holding time is 6-9 h; S50, taking the green body, sintering the green body to obtain a Sr / Co co-doped CCTO giant dielectric ceramic material, the chemical composition of the Sr / Co co-doped CCTO giant dielectric ceramic material is Ca 1-x Sr x Cu 3-y Co y Ti4O 12 , x is 0.1, and y is 0.

1.

2. The method of claim 1, wherein the Sr / Co co-doped CCTO giant dielectric ceramic is prepared by the steps of: preparing a CCTO ceramic by a solid state reaction method; and co-doping Sr and Co to the CCTO ceramic. In step S20, when the precursor powder is pre-sintered, the pre-sintering temperature is 900-1000 DEG C, the temperature rising rate from room temperature to the pre-sintering temperature is 3-5 DEG C / min, and the pre-sintering time is 8-10 h.

3. The method for preparing Sr / Co co-doped CCTO giant dielectric ceramics as described in claim 2, characterized in that: In step S30, the second ball milling speed is 450-550 r / min, and the second ball milling time is 12-20 h.

4. The method for preparing Sr / Co co-doped CCTO giant dielectric ceramics as described in claim 2, characterized in that: The first forming mode comprises: taking the ceramic powder, sequentially subjecting the ceramic powder to pre-compression molding and cold isostatic pressing, the cold isostatic pressing temperature is room temperature, the cold isostatic pressing pressure is 200-250 MPa, and the cold isostatic pressing time is 2-5 min.

5. The method for preparing Sr / Co co-doped CCTO giant dielectric ceramics as described in claim 4, characterized in that: In step S50, the green body sintering temperature is 1050-1100 DEG C, and the sintering holding time is 8-10 h.

6. Application of the ceramic prepared by the method of any one of claims 1-5 to a dielectric capacitor.

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