Bismuth sodium titanate-based dielectric ceramic with energy storage and fluorescent properties and preparation method thereof

Abstract

The application discloses a sodium bismuth titanate-based dielectric ceramic with energy storage and fluorescent characteristics, and has a general chemical composition of 0.75Bi 0.5‑x M' x Na 0.5 TiO3-0.25Sr 0.7 M'' 0.1+y TiO3, x=0-0.3, y=0-0.3, M' is a trivalent rare earth element, the trivalent rare earth element is one of Dy 3+ , Eu 3+ , Ce 3+ , Sm 3+ , or a combination of any two or more than two thereof; M'' is any one or two of Bi 3+ , La 3+ ; and a preparation method of the sodium bismuth titanate-based dielectric ceramic with energy storage and fluorescent characteristics. The application solves the problems of low energy density, great difficulty in fluorescent color tone control and low luminous intensity of existing energy storage-fluorescent ferroelectric ceramics.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of dielectric energy storage ceramic materials, and relates to a sodium bismuth titanate-based dielectric ceramic with energy storage and fluorescence properties and a preparation method of the sodium bismuth titanate-based dielectric ceramic with energy storage and fluorescence properties. BACKGROUND

[0002] The dielectric capacitor with ferroelectric ceramic as a medium has the advantages of high power density (~10 8 W / kg) and fast charging and discharging speed (<1 μs), is very suitable for the use requirements of a pulse power system and an energy storage capacitor field, and is widely applied to scenes such as a pulse power device, an electromagnetic weapon and a hybrid electric vehicle. The prior art explores the characteristic phenomenon of fluorescence spectrum in a ferroelectric lattice field by adding a luminescent element in a ferroelectric material lattice environment, establishes a relationship between physical quantities such as a phase structure and temperature and fluorescence spectrum, develops a nondestructive and noncontact detection means, realizes measurement that cannot be achieved by some traditional measurement methods, and plays a key role in fields such as biomedical materials, anti-counterfeiting and noncontact nondestructive detection due to the excellent fluorescence characteristics and the unique coupling relationship between fluorescence-structure-electric field of the fluorescent ferroelectric ceramic. The crystal structure of the material has a great influence on the ferroelectric energy storage performance and the fluorescence performance, and how to realize the coupling of the two characteristics by adjusting the phase structure is a very promising development direction.

[0003] Chinese Patent "Lead-free ferroelectric up-conversion fluorescent material and preparation method and application thereof" (application date: May 15, 2017; application number: CN201710337929.7; publication date: August 18, 2017; publication number: CN107057699A) discloses a lead-free ferroelectric up-conversion fluorescent material, which is prepared by adding a rare earth element sensitizer Yb 3+ and a rare earth element activator Tm 3+ to replace Bi 3 + , and then realizing defect-based up-conversion luminescence, but the energy storage-fluorescent ferroelectric ceramic still has problems of low energy storage density (less than 3 J / cm 3 ), great difficulty in fluorescence color regulation and low luminescent intensity, which seriously limits its further commercial application. SUMMARY

[0004] An object of the present application is to provide a sodium bismuth titanate-based dielectric ceramic with energy storage and fluorescence properties, which solves the problems of low recoverable energy density and low fluorescence luminescent intensity of the existing energy storage-fluorescent ferroelectric ceramic.

[0005] An object of the present application is to provide a preparation method of a sodium bismuth titanate-based dielectric ceramic with energy storage and fluorescence properties.

[0006] The sodium bismuth titanate-based dielectric ceramic has energy storage and fluorescence characteristics, and has a general chemical composition formula of 0.75Bi 0.5-x M' x Na 0.5 TiO3-0.25Sr 0.7 M'' 0.1+y TiO3, x=0-0.3, y=0-0.3, M' is a trivalent rare earth element, and the trivalent rare earth element is one of Dy 3+ , Eu 3+ , Ce 3+ , Sm 3+ , or a combination of any two or more thereof; M'' is any one or two of Bi 3+ , La 3+ .

[0007] Another technical solution adopted by the present application is a preparation method of the sodium bismuth titanate-based dielectric ceramic with energy storage and fluorescence characteristics, which is implemented according to the following steps:

[0008] Step 1, according to the general chemical composition formula of 0.75Bi 0.5-x M' x Na 0.5 TiO3-0.25Sr 0.7 M'' 0.1+y TiO3, x=0-0.3, y=0-0.3, the raw materials Bi2O3, La2O3, Na2CO3, Dy2O3, Eu2O3, Ce2O3, SrCO3, Sm2O3 and TiO2 are weighed respectively;

[0009] Step 2, the raw materials weighed in step 1 are placed in a roller-type ball mill, and anhydrous ethanol medium is added for grinding and drying, and a ceramic powder precursor is obtained by pre-sintering;

[0010] Step 3, the ceramic powder precursor obtained in step 2 is sequentially subjected to secondary ball milling, glue granulation, tabletting and cold isostatic pressing, and finally a cylindrical ceramic green body is obtained;

[0011] Step 4, the cylindrical ceramic green body obtained in step 3 is subjected to secondary sintering, and the sodium bismuth titanate-based dielectric ceramic with energy storage and fluorescence characteristics is obtained.

[0012] The present application also has the characteristics that

[0013] In step 2, the slurry after uniform ball milling is placed in a glass dish and dried for 8-24 hours, and pre-sintering is performed by placing it in a muffle furnace at 820-860 DEG C for 2-4 hours to obtain a ceramic powder precursor.

[0014] In step 3, the two ball milling modes are roller-type ball milling, the rotation speed is 100-300 r / min, and the ball milling time is 24-36 hours.

[0015] The granulation process in step 3 adopts 5-6wt% polyvinyl alcohol (PVA) as a binder;

[0016] The pressure of the electric tablet press in step 3 is 1-5Pa, and the pressure maintaining time is 1-2min;

[0017] The pressure of the cold isostatic pressing process in step 3 is 100-300MPa, and the pressure maintaining time is 1-2min.

[0018] The secondary sintering in step 4 is carried out in a muffle furnace at 1100℃-1250℃ for 1h-4h.

[0019] The purity of Bi2O3, Na2CO3, La2O3, Dy2O3, Eu2O3, Ce2O3, SrCO3, Sm2O3 and TiO2 selected in step 1 is not less than 99%.

[0020] The sodium bismuth titanate-based dielectric ceramic with energy storage and fluorescence characteristics has white light emission, high fluorescence intensity and large energy storage density, and further has excellent temperature stability and fatigue resistance. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 is the X-ray diffraction pattern of the embodiment 2 of the present application;

[0022] Figure 2 is the scanning electron microscope image of the ceramic of the embodiment 2 of the present application;

[0023] Figure 3 is the electric hysteresis loop diagram of the embodiment 2 of the present application measured at room temperature;

[0024] Figure 4 is the emission spectrum diagram of the embodiment 2 of the present application excited at 389nm at room temperature. DETAILED DESCRIPTION

[0025] The present application will be described in detail below in combination with the drawings and specific embodiments.

[0026] The sodium bismuth titanate-based dielectric ceramic with energy storage and fluorescence characteristics has white light emission, high fluorescence intensity and large energy storage density, and further has excellent temperature stability and fatigue resistance. 0.5- xM' x Na 0.5 TiO3-0.25Sr 0.7 M" 0.1+y TiO3, x = 0 ~ 0.3, y = 0 ~ 0.3, M' is a trivalent rare earth element, the trivalent rare earth element is Dy 3+ , Eu 3+ , Ce 3+ , Sm 3+ one of the elements, or any two, or a combination of two or more; M" is Bi 3+ , La 3+ any one or two of the elements;

[0027] The application also discloses a preparation method of the sodium bismuth titanate-based dielectric ceramic with energy storage and fluorescence characteristics.

[0028] Step 1, according to the chemical composition general formula 0.75Bi 0.5-x M' x Na 0.5 TiO3-0.25Sr 0.7 M" 0.1+y TiO3, x = 0 ~ 0.3, y = 0 ~ 0.3, the raw materials Bi2O3, Na2CO3, La2O3, Dy2O3, Eu2O3, Ce2O3, SrCO3, Sm2O3 and TiO2 are weighed respectively; the purity of Bi2O3, Na2CO3, La2O3, Dy2O3, Eu2O3, Ce2O3, SrCO3, Sm2O3 and TiO2 is not less than 99%.

[0029] Step 2, the raw materials weighed in step 1 are placed in a drum-type ball mill, anhydrous ethanol medium is added, grinding and drying are carried out, and a ceramic powder precursor is obtained through pre-sintering;

[0030] Step 2, the slurry uniformly ball milled is placed in a glass dish and dried for 8h-24h, and the ceramic powder precursor is obtained by sintering at 820℃-860℃ in a muffle furnace for 2h-4h during pre-sintering.

[0031] Step 3, the ceramic powder precursor obtained in step 2 is sequentially subjected to secondary ball milling, glue granulation, tabletting and cold isostatic pressing, and finally a cylindrical ceramic green body is obtained;

[0032] The two ball milling modes are drum-type ball milling, the rotating speed is 100-300r / min, and the ball milling time is 24h-36h;

[0033] 5-6wt% polyvinyl alcohol (PVA) is used as a binder in the glue granulation process;

[0034] The electric tablet presser has a pressure of 1-5 Pa, and the pressure maintaining time is 1-2 min.

[0035] The cold isostatic pressing process has a pressure of 100-300 MPa, and the pressure maintaining time is 1-2 min.

[0036] In step 4, the cylindrical ceramic green body obtained in step 3 is subjected to secondary sintering, and the ceramic is obtained.

[0037] In the secondary sintering, the ceramic is sintered at 1100-1250 DEG C for 1-4 h in a muffle furnace.

[0038] The preparation method of the sodium bismuth titanate-based dielectric ceramic with energy storage and fluorescence characteristics can prepare the sodium bismuth titanate-based binary lead-free dielectric ceramic with high electric field breakdown resistance, high energy storage density and high fluorescence intensity. 0.5-x M' x Na 0.5 TiO3 and Sr 0.7 M" 0.1+y The content ratio of TiO3 is 0.75 and 0.25 respectively, the binary component is located at the morphotropic phase boundary (MPB), the sodium bismuth titanate-based binary lead-free dielectric ceramic at the component has excellent dielectric and ferroelectric characteristics, and higher energy storage density can be obtained.

[0039] The chemical composition general formula of the sodium bismuth titanate-based dielectric ceramic with energy storage and fluorescence characteristics is 0.75Bi 0.5- x M' x Na 0.5 TiO3-0.25Sr 0.7 M" 0.1+y TiO3, wherein x=0-0.3, y=0-0.3, M' represents Dy 3+ , Eu 3+ , Ce 3+ , Sm 3+one or more combinations of elements, M" represents Bi 3+ or La 3+ elements. The preparation method of the sodium bismuth titanate-based binary lead-free dielectric ceramic with energy storage and fluorescence properties comprises the steps of ball milling, pre-sintering, tabletting and final sintering, wherein the ball milling time is 24-36h, the electric tabletting pressure is 1-5Pa, the cold isostatic pressing pressure is 100-300MPa, the pre-sintering process parameters are sintering at 820-860℃ for 2-4h, and the final sintering process parameters are sintering at 1100-1250℃ for 1-4h.

[0040] The sodium bismuth titanate-based binary lead-free dielectric ceramic prepared by the method has the characteristics of high breakdown voltage, high energy storage density, high fluorescence intensity, high fluorescence intensity, single matrix luminescence, energy storage density exceeding 6J / cm 3 , energy storage efficiency exceeding 80%, breakdown field exceeding 500kV / cm, and excellent temperature stability and fatigue resistance, and can be widely applied to the fields of dielectric energy storage capacitors and non-contact nondestructive testing of electronic components.

[0041] Example 1

[0042] The preparation method of the sodium bismuth titanate-based lead-free dielectric ceramic with high energy storage density and fluorescence properties in the embodiment of the application is prepared by a solid phase reaction method, and the specific implementation is as follows:

[0043] Step 1, selecting La2O3, Na2CO3, Eu2O3, SrCO3 and TiO2 with a purity higher than 99% from Alfa Aesar as raw materials; a kind of sodium bismuth titanate-based binary lead-free dielectric ceramic prepared in example 1, the chemical composition is 0.75Bi 0.45 Eu 0.05 Na 0.5 TiO3-0.25Sr 0.7 La 0.3 TiO3, according to the stoichiometric ratio, the raw materials are weighed;

[0044] Step 2, put it in a 200mL polytetrafluoroethylene ball mill tank, add anhydrous ethanol as the ball milling medium, the ball milling speed is 200r / min, and the ball milling time is 30h; pour the slurry after ball milling into a culture dish, and place it in an oven at 100℃ for 12h; put the dried powder into an alumina crucible, cover it and put it into a muffle furnace for pre-sintering to obtain a pre-synthesized powder, set the heating rate to 2℃ / min, the pre-sintering temperature is 850℃, and the holding time is 4h;

[0045] Step 3, secondary ball milling of the calcined powder, using anhydrous ethanol as the medium, the ball milling speed is 200 r / min, and the ball milling time is 36 h; the slurry after the ball milling is poured into an evaporation dish and dried in an oven at 100 DEG C for 12 h; the dried powder is ground in a mortar, then sieved through a 100 mesh sieve, and the sieved powder is bagged for use;

[0046] The sieved uniform powder is added to an appropriate amount of polyvinyl alcohol (PVA) and ground thoroughly to form uniform powder particles; 0.24 g of the above powder is weighed and loaded into a cylindrical mold with a diameter of 10 mm, and pre-pressed into a green body on an electric tablet press at 1 Pa and kept for 1 min; the pre-pressed green body is loaded into a butyronitrile glove, vacuumed, and then placed in a cold isostatic press under the conditions of 200 MPa for 1 min;

[0047] Step 4, the pressed green body is placed in a muffle furnace, and the temperature is raised from room temperature to 550 DEG C at a rate of 1 DEG C / min, and then kept for 10 h to remove the PVA added during the granulation process; the green body is sintered in a muffle furnace at a sintering temperature of 1160 DEG C for 3 h, and then naturally cooled in the furnace; during the sintering process, a powder of the same composition is covered on the ceramic green body to reduce the element volatilization; the sintered ceramic sample is polished on 800 mesh, 1500 mesh and 2000 mesh sandpaper; silver paste is applied to the upper and lower surfaces of the sample, and then placed in a muffle furnace at 500 DEG C for 30 min for testing the electrical properties.

[0048] Example 2

[0049] The preparation method of the sodium bismuth titanate-based lead-free dielectric ceramic with high energy storage density and fluorescent properties in the embodiment 2 of the application is prepared by a solid phase reaction method, and the specific implementation is as follows:

[0050] Step 1, Bi2O3, Na2CO3, Dy2O3, SrCO3 and TiO2 with a purity higher than 99% from Alfa Aesar are selected as raw materials; a sodium bismuth titanate-based binary lead-free dielectric ceramic prepared in the embodiment 2 has a chemical composition of 0.75Bi 0.35 Dy 0.15 Na 0.5 TiO3-0.25Sr 0.7 Bi 0.2 TiO3, and the raw materials are weighed according to the stoichiometric ratio;

[0051] Step 2, according to the chemical formula, the powder is weighed, and then is placed in a 200 mL polytetrafluoroethylene ball mill tank, anhydrous ethanol is added as a medium, the ball milling speed is 150 r / min, and the ball milling time is 24 h; the slurry after the above ball milling is poured into an evaporating dish, and is placed in an oven for drying at 100 ℃ for 24 h; the dried powder is loaded into an alumina crucible, is covered, and is placed in a muffle furnace for pre-sintering to obtain a pre-synthesized powder, the temperature rising rate is set to 3 ℃ / min, the pre-sintering temperature is 860 ℃, the holding time is 4 h, and then the furnace is naturally cooled down;

[0052] Step 3, the pre-sintered powder is ball milled for the second time, anhydrous ethanol is used as a medium, the ball milling speed is 150 r / min, and the ball milling time is 36 h; the slurry after the above ball milling is poured into an evaporating dish, and is placed in an oven for drying at 100 ℃ for 12 h; the dried powder is placed in a mortar for grinding, and then is sieved through a 100-mesh sieve, and the sieved powder is bagged for later use;

[0053] The sieved uniform powder is added with an appropriate amount of polyvinyl alcohol (PVA) and is ground to form uniform powder particles; 0.25 g of the above powder is weighed and is loaded into a cylindrical mold with a diameter of 10 mm, is pre-pressed and formed on an electric tablet press at 2 Pa, and is kept for 2 min; the pre-pressed and formed green body is loaded into a butyronitrile glove, is vacuumized, and then is placed into a cold isostatic pressing machine under the condition that the pressure is 300 MPa and the holding time is 1 min;

[0054] Step 4, the pre-pressed and formed green body is placed in a muffle furnace, the temperature is raised to 600 ℃ at a temperature rising rate of 2 ℃ / min from room temperature, and then is kept for 8 hours to remove the PVA added in the granulation process; the above green body is placed in a muffle furnace for high-temperature sintering, the sintering temperature is 1200 ℃ and the holding time is 4 h, and then the furnace is naturally cooled down. During the sintering process, the powder of the same component is covered on the ceramic green body to reduce the element volatilization; the sintered ceramic sample is ground and polished on a 800-mesh, 1200-mesh and 2000-mesh sandpaper respectively; silver is coated on the upper and lower surfaces of the sample, and then is placed in a muffle furnace at 550 ℃ for 20 min, for testing the dielectric properties; a Pt electrode is sputtered on the surface of the sample by using a magnetron sputtering instrument, for testing the electric hysteresis loop.

[0055] The X-ray diffraction pattern of the ceramic component in Example 2 is shown in Figure 1 As can be seen from the figure, the BNT-based ceramic prepared in the application has a perovskite structure, and there is no second phase, which indicates that the formula proportion of the application is effective, the preparation process is reasonable, and the doped elements successfully enter the corresponding lattice sites.

[0056] The scanning electron microscope photograph of the ceramic prepared in Example 2 is shown in Figure 2As shown in the figure, the ceramic presents a dense microstructure, the grain size is about 2 microns, the ceramic surface has few holes, which proves that the ceramic is combined densely after sintering, so the ceramic has a high breakdown electric field.

[0057] The electric hysteresis loop of the ceramic at room temperature is shown in Figure 2. Figure 3 As shown in the figure, the electric hysteresis loop of the ceramic composition is thin, and the residual polarization is only 5 mu C / cm 2 under an ultra-high breakdown electric field of 600 kV / cm 2 , and the maximum polarization strength exceeds 40 mu C / cm 3 . Through calculation, the energy storage density and energy storage efficiency of the ceramic are 7.02 J / cm 0.5 and 81.0%, respectively. The excellent breakdown electric field and energy storage performance prove that the multifunctional ferroelectric ceramic material disclosed in the application has high performance characteristics and advantages.

[0058] The emission spectrum of Example 2 at room temperature under 389 nm excitation is shown in Figure 3. Figure 4 As shown in the figure, the emission spectrum of the ceramic composition has two obvious emission spectrum peaks at 483 and 576 nm, which correspond to the blue light and yellow light emission of the Dy element respectively, so excellent single-matrix white light can be obtained by combining blue light and yellow light.

[0059] Example 3

[0060] The preparation method of the sodium bismuth titanate-based lead-free dielectric ceramic with high energy storage density and fluorescent properties in the embodiment of the application is prepared by a solid phase reaction method, and the specific implementation steps are as follows:

[0061] Step 1, select Bi2O3, La2O3, Na2CO3, SrCO3 and TiO2 with a purity higher than 99% from Alfa Aesar as raw materials; a sodium bismuth titanate-based binary lead-free dielectric ceramic is prepared in Example 3, and the chemical composition is 0.75Bi 0.5 Na 0.5 TiO3-0.25Sr 0.7 Bi 0.1 La 0.3 TiO3, and the raw materials are weighed according to the stoichiometric ratio;

[0062] Step 2, place in a 200 mL polytetrafluoroethylene ball mill tank, add anhydrous ethanol as a ball milling medium, the ball milling speed is 300 r / min, and the ball milling time is 36 h; pour the slurry after ball milling into a culture dish, and place it in an oven for drying at 80℃ for 24 h; put the dried powder into an alumina crucible, cover it and put it into a muffle furnace for pre-synthesis, set the heating rate to 3℃ / min, the pre-synthesis temperature is 820℃, and the holding time is 2 h;

[0063] Step 3, secondary ball milling of the calcined powder, with anhydrous ethanol as the medium, the ball milling speed is 300 r / min, and the ball milling time is 36 h; the slurry after the above ball milling is poured into an evaporation dish and dried at 80℃ in an oven for 24 h; the dried powder is placed in a mortar and ground thoroughly, and then sieved through a 100 mesh sieve, and the sieved powder is bagged for use;

[0064] The sieved uniform powder is added to an appropriate amount of polyvinyl alcohol (PVA) and ground thoroughly to form uniform powder particles; 0.24 g of the above powder is weighed and loaded into a cylindrical mold with a diameter of 10 mm, and pre-pressed into a tablet on an electric tablet press at 5 Pa and held for 2 min; the pre-pressed green body is loaded into a butyronitrile glove, vacuumed, and then placed in a cold isostatic press under the conditions of 150 MPa for 2 min;

[0065] Step 4, the pressed green body is placed in a muffle furnace, and the temperature is raised from room temperature to 600℃ at a rate of 3℃ / min, and then held for 8 h to remove the PVA added during the granulation process; the above green body is sintered in a muffle furnace at a sintering temperature of 1200℃ for 2 h, and then naturally cooled in the furnace. During the sintering process, powder of the same composition is covered on the ceramic green body to reduce the element volatilization;

[0066] The sintered ceramic sample is polished on 800 mesh, 1500 mesh and 2000 mesh sandpaper respectively; silver paste is applied to the upper and lower surfaces of the sample, and then placed in a muffle furnace at 500℃ for 20 min for testing its electrical properties.

[0067] Example 4

[0068] The preparation method of the sodium bismuth titanate-based lead-free dielectric ceramic with high energy storage density and fluorescent properties in the embodiment 4 of the application is prepared by a solid phase reaction method, and the specific implementation is as follows:

[0069] Step 1, select Bi2O3, La2O3, Na2CO3, Dy2O3, Eu2O3, SrCO3 and TiO2 with a purity higher than 99% from Alfa Aesar as raw materials; a sodium bismuth titanate-based binary lead-free dielectric ceramic is prepared in the embodiment 4, and the chemical composition is 0.75Bi 0.3 Dy 0.1 Eu 0.1 Na 0.5 TiO3-0.25Sr 0.7 Bi 0.2 La 0.1 TiO3, according to the stoichiometric ratio;

[0070] Step 2, place in a 200 mL polytetrafluoroethylene ball mill tank, add anhydrous ethanol as the ball milling medium, the ball milling speed is 150 r / min, the ball milling time is 36 h; pour the slurry after ball milling into a culture dish, and place it in an oven at 80℃ for 12 h; the dried powder is loaded into an alumina crucible, covered and placed in a muffle furnace for pre-synthesis to obtain a pre-synthesized powder, the temperature rising rate is set to 5℃ / min, the pre-synthesis temperature is 840℃, and the holding time is 4 h;

[0071] Step 3, the pre-synthesized powder is ball milled again, anhydrous ethanol is used as the medium, the ball milling speed is 150 r / min, and the ball milling time is 36 h; pour the slurry after ball milling into an evaporation dish, and place it in an oven at 80℃ for 12 h; the dried powder is placed in a mortar and ground thoroughly, then sieved through a 100 mesh sieve, and the sieved powder is packed for use;

[0072] The sieved uniform powder is added to an appropriate amount of polyvinyl alcohol (PVA) and ground thoroughly to form uniform powder particles; 0.24 g of the above-mentioned powder is weighed and loaded into a cylindrical mold with a diameter of 10 mm, and is pre-pressed into a green body on an electric tablet press at 3 Pa and held for 1 min; the pre-pressed green body is loaded into a butyronitrile glove, vacuumed, and then placed in a cold isostatic pressing machine under the condition of 200 MPa for 1 min;

[0073] Step 4, the pressed green body is placed in a muffle furnace, and the temperature is raised to 500℃ at a rate of 2℃ / min from room temperature, and then held for 6 hours to remove the PVA added during the granulation process; the above-mentioned green body is placed in a muffle furnace for high-temperature sintering, the sintering temperature is 1100℃ and the holding time is 3 h, and then the furnace is naturally cooled down; during the sintering process, a powder of the same composition is covered on the ceramic green body to reduce the element volatilization;

[0074] The sintered ceramic sample is polished on 800 mesh, 1500 mesh and 2000 mesh sandpaper respectively; silver paste is applied to the upper and lower surfaces of the sample, and then placed in a muffle furnace at 520℃ for 30 min for testing its electrical properties.

[0075] Example 5

[0076] The preparation method of the sodium bismuth titanate-based lead-free dielectric ceramic with high energy storage density and fluorescent properties in the embodiment 5 of the application is prepared by a solid phase reaction method, and the specific implementation is as follows:

[0077] Step 1, select Bi2O3, La2O3, Na2CO3, Ce2O3, Sm2O3, SrCO3 and TiO2 with a purity higher than 99% from Alfa Aesar as raw materials; in the embodiment 5, a sodium bismuth titanate-based binary lead-free dielectric ceramic is prepared, and the chemical composition is 0.75Bi 0.2 Ce 0.1 Sm0.2 Na 0.5 TiO3-0.25Sr 0.7 Bi 0.1 La 0.1 TiO3, according to the stoichiometric ratio of raw materials;

[0078] Step 2, placed in a 200 mL polytetrafluoroethylene ball mill tank, add anhydrous ethanol as ball milling medium, ball milling speed is 200 r / min, ball milling time is 24 h; the slurry after the above ball milling is poured into a petri dish, placed in an oven at 100℃ drying 24 h; the dried powder is loaded into an alumina crucible, cover and put into a muffle furnace to obtain a pre-synthesized powder, set the heating rate to 3℃ / min, the pre-sintering temperature is 860℃, and the holding time is 2h;

[0079] Step 3, the pre-sintered powder is ball milled again, anhydrous ethanol as medium, ball milling speed is 200 r / min, ball milling time is 24 h; the slurry after the above ball milling is poured into an evaporation dish, placed in an oven at 100℃ drying 24 h; the dried powder is placed in a mortar and ground thoroughly, then sieved through a 100 mesh sieve, and the sieved powder is packed for use;

[0080] The sieved uniform powder is added to an appropriate amount of polyvinyl alcohol (PVA) and ground thoroughly to form uniform powder particles; 0.24g of the above powder is weighed and loaded into a cylindrical mold with a diameter of 10mm, pre-pressed into a green body on an electric tablet press at 4Pa and held for 2min; the pre-pressed green body is placed in a butyronitrile glove, vacuumed, and then placed in a cold isostatic pressing machine under the conditions of 300MPa for 2min;

[0081] Step 4, the pressed green body is placed in a muffle furnace, heated from room temperature to 500℃ at a rate of 1℃ / min, and then held for 10 hours to remove the PVA added during granulation; the green body is placed in a muffle furnace for high temperature sintering, with a sintering temperature of 1250℃ for 1h, and then naturally cooled in the furnace. During sintering, powder of the same composition is covered on the ceramic green body to reduce element volatilization; the sintered ceramic sample is ground and polished on 800 mesh, 1500 mesh and 2000 mesh sandpaper respectively; silver paste is applied to the upper and lower surfaces of the sample, and then placed in a muffle furnace at 600℃ for 15min for testing its electrical properties.

Claims

1. A method for preparing sodium bismuth titanate-based dielectric ceramics having both energy storage and fluorescence properties, characterized in that: Please follow the steps below to implement it: Step 1: The chemical formula is 0.75Bi 0.5-x M´ x Na 0.5 TiO3-0.25Sr 0.7 M´´ 0.1+y TiO3,0< x ≤0.3, 0< y ≤0.3, M' uses trivalent rare earth elements, trivalent rare earth elements are Dy 3+ 、Eu 3+ 、Ce 3+ 、Sm 3+ One element, or any two elements, or any combination of two or more elements; M´´ is Bi 3+ 、La 3+ Any one or two of the elements, weigh the raw materials Bi2O3, La2O3, Na2CO3, Dy2O3, Eu2O3, Ce2O3, SrCO3, Sm2O3 and TiO2 respectively; Step 2: Place the raw materials weighed in step 1 in a drum ball mill, add anhydrous ethanol as a medium, grind and dry, and pre-sinter to obtain a ceramic powder precursor; Step 3: The ceramic powder precursor obtained in step 2 is subjected to secondary ball milling, granulation with glue, tableting and cold isostatic pressing in sequence to finally obtain a cylindrical ceramic green body; Step 4: performing secondary sintering on the cylindrical ceramic green body obtained in step 3; In step 2, the slurry after ball milling is placed in a glass dish and dried for 8h-24h, and then placed in a muffle furnace for sintering at 820°C-860°C for 2h-4h to obtain a ceramic powder precursor; The two ball milling processes in step 3 are performed by drum milling, with a rotation speed of 100-300 r / min and a ball milling time of 24h-36h; In the step 3, 5-6 wt % of polyvinyl alcohol is used as a binder during the granulation process; In step 3, the pressure of the electric tablet press is 1-5 Pa, and the holding time is 1-2 min; The pressure during the cold isostatic pressing process in step 3 is 100-300 MPa, and the holding time is 1-2 minutes.

2. The method for preparing sodium bismuth titanate-based dielectric ceramics having both energy storage and fluorescence properties according to claim 1, characterized in that: During the secondary sintering in step 4, the steel is placed in a muffle furnace and sintered at 1100° C.-1250° C. for 1 hour-4 hours.

3. The method for preparing sodium bismuth titanate-based dielectric ceramics having both energy storage and fluorescence properties according to claim 1, characterized in that: In the step 1, the purity of Bi2O3, La2O3, Na2CO3, Dy2O3, Eu2O3, Ce2O3, SrCO3, Sm2O3 and TiO2 selected is not less than 99%.

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