CN101786874B - Process method for preparing low residual voltage ZnO varistor ceramic - Google Patents
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- 238000000034 method Methods 0.000 title claims abstract description 45
- 239000000919 ceramic Substances 0.000 title claims abstract description 26
- 230000008569 process Effects 0.000 title claims abstract description 14
- 239000013078 crystal Substances 0.000 claims abstract description 65
- 238000005245 sintering Methods 0.000 claims abstract description 50
- 239000002994 raw material Substances 0.000 claims abstract description 42
- 238000002360 preparation method Methods 0.000 claims abstract description 23
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 15
- 239000000203 mixture Substances 0.000 claims description 27
- 238000000498 ball milling Methods 0.000 claims description 25
- 239000000463 material Substances 0.000 claims description 16
- 239000008367 deionised water Substances 0.000 claims description 14
- 229910021641 deionized water Inorganic materials 0.000 claims description 14
- 238000009413 insulation Methods 0.000 claims description 13
- 239000000758 substrate Substances 0.000 claims description 12
- 238000005516 engineering process Methods 0.000 claims description 11
- 238000010792 warming Methods 0.000 claims description 11
- 239000002245 particle Substances 0.000 claims description 10
- 239000011230 binding agent Substances 0.000 claims description 9
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims description 8
- 229910004298 SiO 2 Inorganic materials 0.000 claims description 7
- 238000005469 granulation Methods 0.000 claims description 7
- 230000003179 granulation Effects 0.000 claims description 7
- 238000004519 manufacturing process Methods 0.000 claims description 7
- 229910052782 aluminium Inorganic materials 0.000 claims description 6
- 238000010298 pulverizing process Methods 0.000 claims description 5
- 229910052797 bismuth Inorganic materials 0.000 claims description 2
- XLOMVQKBTHCTTD-UHFFFAOYSA-N Zinc monoxide Chemical compound [Zn]=O XLOMVQKBTHCTTD-UHFFFAOYSA-N 0.000 abstract description 88
- 230000003247 decreasing effect Effects 0.000 abstract description 2
- WMWLMWRWZQELOS-UHFFFAOYSA-N bismuth(iii) oxide Chemical compound O=[Bi]O[Bi]=O WMWLMWRWZQELOS-UHFFFAOYSA-N 0.000 abstract 4
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 abstract 2
- QDOXWKRWXJOMAK-UHFFFAOYSA-N dichromium trioxide Chemical compound O=[Cr]O[Cr]=O QDOXWKRWXJOMAK-UHFFFAOYSA-N 0.000 abstract 2
- NUJOXMJBOLGQSY-UHFFFAOYSA-N manganese dioxide Chemical compound O=[Mn]=O NUJOXMJBOLGQSY-UHFFFAOYSA-N 0.000 abstract 2
- UPWOEMHINGJHOB-UHFFFAOYSA-N oxo(oxocobaltiooxy)cobalt Chemical compound O=[Co]O[Co]=O UPWOEMHINGJHOB-UHFFFAOYSA-N 0.000 abstract 2
- GHPGOEFPKIHBNM-UHFFFAOYSA-N antimony(3+);oxygen(2-) Chemical compound [O-2].[O-2].[O-2].[Sb+3].[Sb+3] GHPGOEFPKIHBNM-UHFFFAOYSA-N 0.000 abstract 1
- 229910052681 coesite Inorganic materials 0.000 abstract 1
- 229910052906 cristobalite Inorganic materials 0.000 abstract 1
- 238000003754 machining Methods 0.000 abstract 1
- 239000000377 silicon dioxide Substances 0.000 abstract 1
- 235000012239 silicon dioxide Nutrition 0.000 abstract 1
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Abstract
The invention relates to a process method for preparing low residual voltage ZnO varistor ceramic and belongs to the technical field of residual voltage ZnO varistor ceramic machining; the residual voltage ZnO varistor ceramic preparation process is based on the sintering process and seeded solution growth and includes the raw materials of ZnO, Bi2O3, MnO2, Sb2O3, Co2O3, SiO2, Al (NO3) 3 9H2O and Cr2O3; the preparation method includes that: ZnO, Bi2O3 and Al (NO3) 3 9H2O in the raw material formula are adopted to be ground by a ball mill and dried as seed crystal raw material; the seed crystal raw material is placed in a high temperature electric resistance furnace for pre-sintering to from seed crystal lumps as the first step, and the seed crystal lumps are cooled to normal temperature in the furnace; and then the seed crystal lumps are ground by the ball mill again and sieved to obtain seed crystals; all remaining raw materials, the seed crystals and PVA solution are mixed and ground by the ball mill to be dried, sieved and granulated with water content and pressed into blanks; and the blanks are sintered and cooled to normal temperature in the second step. The process method not only can reduce grain resistivity and ZnO varistor residual voltage, but also restrains the increasing of current leakage and the decreasing of non-linear coefficient. The low residual voltage ZnO varistor ceramic has higher performance and is more suitable for industrial application.
Description
Technical field
The invention belongs to the processing technique field of low residual voltage ZnO varistor ceramic, particularly a kind of preparation of seed crystal method and sintered ceramic technology of new two-step sintering.
Background technology
ZnO varistor is to be primary raw material with ZnO, has added a spot of Bi
2O
3, MnO
2, Sb
2O
3, Co
2O
3, SiO
2And Cr
2O
3Deng, adopt ceramic sintering process to be prepared from.Because the advantage of its good non-linear behaviour and big discharge capacity, since came to light the seventies in 19th century, ZnO varistor was widely used in electric power system lightning protection and electric equipment protection as the core parts of electric power system lightning arrester.Many weeks, insulation costs accounts for the major part in the power engineering cost, and along with the raising of voltage class of electric power system, insulation consumes huger under the voltage levels.And the insulation par of electric power system flat be with the residual voltage protection level of lightning arrester as the basis, therefore reduce the residual voltage level of ZnO varistor lightning arrester, can reduce insulating requirements significantly, consume and construction cost thereby reduce insulation significantly.The low residual voltage Zinc-oxide piezoresistor of research becomes one of research focus of academia and industrial quarters immediately.
The turn on process of ZnO varistor can be divided into three phases: little Current Zone, middle Current Zone and big Current Zone.Little Current Zone (＜10
-4A/cm
2) being defined as the prebreakdown district, crystal boundary demonstrates high-impedance state in this zone, and current/voltage (I-V) curve shows as ohm property.In Current Zone be the nonlinear resistance district, this regional electric current sharply increases and voltage increases slowly, this area I-V characteristic is influenced jointly by ZnO crystal grain and ZnO crystal boundary and determines.Big Current Zone (＞10
3A/cm2) become ohm property again, its performance is mainly determined by the ZnO grain resistance.No matter be that the ZnO grain resistance all affects the I-V characteristic in middle Current Zone or big Current Zone.Reduce the residual voltage of ZnO varistor, must reduce the resistivity of ZnO varistor.Research according in the past shows, adds a certain amount of donor ion and can obviously improve the resistivity of ZnO crystal grain, thereby reach the purpose that reduces residual voltage.Find in the investigation of materials that the donor ion that can reduce resistivity has Ga, Al and In.Adopt the Al ion to add in the ZnO varistor raw material in the existing commercial production mostly as donor ion.The production technology of Jiangsu new people's power equipment Co., Ltd is with the raw materials mix ball milling after 2-5 hour or the part trace mineral supplement is carried out low temperature presintering, moisture granulation, moulding then, and in high temperature furnace once sintered one-tenth piezo-resistance.Generally only added the 0.005mol%Al ion as donor ion, it is also not obvious therefore to cause the ZnO varistor rate to reduce.If but add a large amount of Al ions as donor ion, can get into spinelle phase and thick grain boundary layer owing to adding the Al ion again, make that the resistivity decreased of response region is obvious, can cause also that in addition interface state density descends and the reduction of barrier height.Make the leakage current of ZnO varistor sharply increase, non linear coefficient descends.When Al ion addition reaches 0.05mol%, leakage current density will increase to 20 μ A/cm
2More than, non linear coefficient drops to below 30, can not satisfy the demand of commercial Application.
Summary of the invention
The objective of the invention is to for overcoming the weak point of prior art, develop a kind of process of new preparation low residual voltage ZnO varistor ceramic, make this material have higher performance and be more suitable for commercial Application.
A kind of process for preparing low residual voltage ZnO varistor ceramic that the present invention proposes; It is characterized in that; This method is based on the preparation technology of the low residual voltage ZnO varistor ceramic of two-step sintering method and seed crystal method, and this preparation method's composition of raw materials comprises: ZnO (92.7-97mol%), Bi
2O
3(0.4-0.9mol%), MnO
2(0.4-0.7mol%), Sb
2O
3(0.5-1.5mol%), Co
2O
3(0.5-1.5mol%), SiO
2(0.8-1.7mol%), Al (NO
3)
39H
2O (0.1-0.4mol%) and Cr
2O
3(0.3-0.7mol%); This method may further comprise the steps:
1) preparation of seed crystal and first step sintering:
(11) adopt the ZnO of the 20%-50% of total amount in the composition of raw materials, the Bi of 0%-20%
2O
3With whole Al (NO
3)
39H
2O; Place the ball grinder that is added with deionized water or alcohol, ball milling 8-12 hour, dry then as seed material;
(12) the dried seed material of ball milling is put into high-temperature electric resistance furnace, under 1200-1350 ℃, carry out first step pre-burning and became the seed crystal lump in 3-6 hour, cool to normal temperature with the furnace;
(13) with after the pulverizing of the seed crystal lump after the sintering, place ball grinder, add deionized water or alcohol ball milling 4-8 hour; Chose the seed crystal of 200-500 mesh sieve then, obtaining particle diameter is the seed crystal below the 75um;
2) raw materials mix and the second step sintering
(21) seed crystal that all remaining raw materials, step 13) is obtained and mix according to 5% (wt) PVA solution that every gram raw material adds 0.5mL; In ball grinder, added the deionized water ball milling 8-12 hour; Dry, cross 70-150 purpose sieve then; The method of pressure forming is adopted in moisture granulation then, and it is pressed into base substrate;
(22) sample with base substrate carries out the second step sintering in airtight high-temperature electric resistance furnace; Be warming up to holding temperature (350-550 ℃) from room temperature; Be incubated 4-6 hour and carry out binder removal, and then be warming up to sintering temperature (1150 ℃-1200 ℃) through 18-23 hour, insulation is 3-6 hour under sintering temperature; Make ceramic sintered compact, be cooled to normal temperature with stove then.
Technical characterstic of the present invention and beneficial effect:
The present invention is through strict burning process flow process and the control process parameters of changing; Can control constituent and the structural change of this material in the preparation process artificially; When reducing the grain resistance rate and reducing the ZnO varistor residual voltage, the growth of leakage current and the decline of non linear coefficient have been suppressed again.Thereby make this material have higher performance and be more suitable for commercial Application.
Description of drawings
Fig. 1 for process of the present invention and traditional handicraft the effect contrast figure.
Embodiment
A kind of process for preparing low residual voltage ZnO varistor ceramic that the present invention proposes combines embodiment to specify as follows:
Preparation technology's method of the present invention is characterized in that, this method is based on the preparation technology of the low residual voltage ZnO varistor ceramic of two-step sintering method and seed crystal method, and this preparation method's composition of raw materials comprises: ZnO (92.7-97mol%), Bi
2O
3(0.4-0.9mol%), MnO
2(0.4-0.7mol%), Sb
2O
3(0.5-1.5mol%), Co
2O
3(0.5-1.5mol%), SiO
2(0.8-1.7mol%), Al (NO
3)
39H
2O (0.1-0.4mol%) and Cr
2O
3(0.3-0.7mol%); This method may further comprise the steps:
1) preparation of seed crystal and first step sintering:
(11) adopt the ZnO of the 20%-50% of total amount in the composition of raw materials, the Bi of 0%-20%
2O
3With whole Al (NO
3)
39H
2O; Place the ball grinder that is added with deionized water or alcohol, ball milling 8-12 hour, dry then as seed material;
(12) the dried seed material of ball milling is put into high-temperature electric resistance furnace, under 1200-1350 ℃, carry out first step pre-burning and became the seed crystal lump in 3-6 hour, cool to normal temperature with the furnace;
(13) with after the pulverizing of the seed crystal lump after the sintering, place ball grinder, add deionized water or alcohol ball milling 4-8 hour; Chose the seed crystal of 200-500 mesh sieve then, obtaining particle diameter is the seed crystal below the 75um;
2) raw materials mix and the second step sintering
(21) seed crystal that all remaining raw materials, step 13) is obtained and mix according to 5% (wt) PVA solution that every gram raw material adds 0.5mL; In ball grinder, added the deionized water ball milling 8-12 hour; Dry, cross 70-150 purpose sieve then; The method of pressure forming is adopted in moisture granulation then, and it is pressed into base substrate;
(22) base substrate is carried out the second step sintering in airtight high-temperature electric resistance furnace; Be warming up to holding temperature (350-550 ℃) from room temperature; Be incubated 4-6 hour and carry out binder removal, and then be warming up to sintering temperature (1150 ℃-1200 ℃) through 18-23 hour, insulation is 3-6 hour under sintering temperature; Make ceramic sintered compact, be cooled to normal temperature with stove then.
Beneficial effect of the present invention is: the ZnO seed crystal that this technology will contain the Al ion is descending first step sintering 3-6 after individual hour in advance about 1300 degree, the Al ion dissolves each other and gets in the ZnO seed crystal, makes seed crystal resistivity significantly descend.When seed crystal and surplus stock mix when carrying out normal (second step) ceramic post sintering; Because the particle diameter of seed crystal is between 75 μ m-25 μ m; The about 0.6 μ m of the average particle size particle size of ZnO in the raw material; Much smaller than the seed crystal particle diameter, according to the grain growth rule, the crystal grain of larger radius of curvature will adsorb the crystal grain of small curvature radius and form new crystal grain.Therefore in the process of grain growth, will be the center growth with the seed crystal.After sintering finished, the seed crystal of low-resistivity just was enclosed in the middle of the crystal grain of ZnO, so the diffuser efficiency of Al ion obtained very obvious suppression, and when being controlled at its residual voltage ratio below 1.5, its leakage current is less than 1 μ A/cm
2, non linear coefficient is more than 50, and voltage gradient gets into grain boundary layer and spinelle probability mutually thereby the method has suppressed the Al ion on root more than 220V/mm, make ZnO varistor reach the effect of desirable low residual voltage.
Embodiment one
The composition of raw materials of present embodiment is following:
This low residual voltage ZnO varistor ceramic raw material clicks the ratio preparation: ZnO (94.8mol%), Bi
2O
3(0.7mol%), MnO
2(0.5mol%), Sb
2O
3(1mol%), Co
2O
3(1mol%), SiO
2(1.25mol%), Al (NO
3)
39H
2O (0.25mol%) and Cr
2O
3(0.5mol%); The method of present embodiment may further comprise the steps:
1) preparation of seed crystal and first step sintering:
(11) 25% ZnO and whole Al (NO in the employing composition of raw materials
3)
39H
2O; Place the ball grinder ball milling 10 hours that adds deionized water, dry then as seed material;
(12) the dried seed material of ball milling is put into high-temperature electric resistance furnace, became the seed crystal lump in 4 hours, cool to normal temperature with the furnace 1300 ℃ of following first step pre-burnings;
(13) the seed crystal lump after the sintering is pulverized after, place ball grinder to add deionized water or alcohol ball milling 10 hours; Chose the seed crystal of 200 mesh sieves then, obtaining particle diameter is the following seed crystals of 75 μ m;
2) raw materials mix and the second step sintering
(21) seed crystal that all remaining raw materials, step 13) is obtained and mix according to 5% (wt) PVA solution that every gram raw material adds 0.5mL; Ball milling is 10 hours in ball grinder, dries, crosses 100 purposes sieve then, moisture granulation; Adopt the method for pressure forming then; Its pressure is the disk base substrate of 2cm diameter 2mm thickness, and pressure is 200MPa, and the dwell time is 3 minutes;
(22) base substrate is carried out the second step sintering in airtight high-temperature electric resistance furnace; Be warming up to holding temperature (400 ℃) gradually from room temperature; Be incubated 4 hours and carry out binder removal, and then be warming up to sintering temperature (1200 ℃) gradually, insulation is 4.5 hours under sintering temperature; Make ceramic sintered compact, be cooled to normal temperature with stove then.Temperature curve is:
From room temperature to 400 ℃, 2 hours heating-up times;
Be incubated binder removals 6 hours at 400 ℃;
From 400 ℃ to 1000 ℃, 15 hours heating-up times;
From 1000 ℃ to 1100 ℃, 3 hours heating-up times;
From 1100 ℃ to 1200 ℃, 3 hours heating-up times;
1200 ℃ of insulations 4.5 hours;
Cool to normal temperature with the furnace.
Embodiment two
The composition of raw materials of present embodiment is following:
This low residual voltage ZnO varistor ceramic raw material clicks the ratio preparation: ZnO (92.7mol%), Bi
2O
3(0.9mol%), MnO
2(0.7mol%), Sb
2O
3(1.5mol%), Co
2O
3(1.5mol%), SiO
2(1.7mol%), Al (NO
3)
39H
2O (0.4mol%) and Cr
2O
3(0.7mol%); The method of present embodiment may further comprise the steps:
1) preparation of seed crystal and first step sintering:
(11) 25% ZnO, 25% Bi in the employing composition of raw materials
2O
3With whole Al (NO
3)
39H
2O; Place the ball grinder ball milling 12 hours that adds deionized water, dry then as seed material;
(12) the dried seed material of ball milling is put into high-temperature electric resistance furnace, became the seed crystal lump in 6 hours, cool to normal temperature with the furnace 1300 ℃ of following first step pre-burnings;
(13) with after the pulverizing of the seed crystal lump after the sintering, place ball grinder to add the alcohol ball milling 12 hours; Chose the seed crystal of 500 mesh sieves then, obtaining particle diameter is the following seed crystals of 25 μ m;
2) raw materials mix and the second step sintering
(21) seed crystal that all remaining raw materials, step 13) is obtained and mix according to 5% (wt) PVA solution that every gram raw material adds 0.5mL; Ball milling is 10 hours in ball grinder, dries, crosses 100 purposes sieve then, moisture granulation; Adopt the method for pressure forming then; Its pressure is the disk base substrate of 2cm diameter 2mm thickness, and pressure is 200MPa, and the dwell time is 3 minutes;
(22) base substrate is carried out the second step sintering in airtight high-temperature electric resistance furnace; Be warming up to holding temperature (400 ℃) gradually from room temperature; Be incubated 6 hours and carry out binder removal, and then be warming up to sintering temperature (1150 ℃) gradually, insulation is 4.5 hours under sintering temperature; Make ceramic sintered compact, be cooled to normal temperature with stove then.Temperature curve is:
From room temperature to 400 ℃, 2 hours heating-up times;
Be incubated binder removals 4 hours at 400 ℃;
From 400 ℃ to 1000 ℃, 15 hours heating-up times;
From 1000 ℃ to 1100 ℃, 3 hours heating-up times;
From 1100 ℃ to 1150 ℃, 3 hours heating-up times;
1150 ℃ of insulations 4.5 hours;
Cool to normal temperature with the furnace.
Embodiment three
The composition of raw materials of present embodiment is following:
This low residual voltage ZnO varistor ceramic raw material clicks the ratio preparation: ZnO (97mol%), Bi
2O
3(0.4mol%), MnO
2(0.4mol%), Sb
2O
3(0.5mol%), Co
2O
3(0.5mol%), SiO
2(0.8mol%), Al (NO
3)
39H
2O (0.1mol%) and Cr
2O
3(0.3mol%); The method of present embodiment may further comprise the steps:
1) preparation of seed crystal and first step sintering:
(11) 50% ZnO and whole Al (NO in the employing composition of raw materials
3)
39H
2O; Place the ball grinder ball milling 8 hours that adds deionized water, dry then as seed material;
(12) the dried seed material of ball milling is put into high-temperature electric resistance furnace, became the seed crystal lump in 3 hours, cool to normal temperature with the furnace 1300 ℃ of following first step pre-burnings;
(13) with after the pulverizing of the seed crystal lump after the sintering, place ball grinder to add the deionized water ball milling 8 hours; Chose the seed crystal of 200 mesh sieves then, obtaining particle diameter is the seed crystal below the 75 μ m;
2) raw materials mix and the second step sintering
(21) seed crystal that all remaining raw materials, step 13) is obtained and mix according to 5% (wt) PVA solution that every gram raw material adds 0.5mL; Ball milling is 10 hours in ball grinder, dries, crosses 150 purposes sieve then, moisture granulation; Adopt the method for pressure forming then; Its pressure is the disk base substrate of 2cm diameter 2mm thickness, and pressure is 200MPa, and the dwell time is 3 minutes;
(22) base substrate is carried out the second step sintering in airtight high-temperature electric resistance furnace; Heat up slowly to holding temperature (400 ℃) from room temperature; Be incubated 6 hours and carry out binder removal, and then slowly be warming up to sintering temperature (1200 ℃), insulation is 4.5 hours under sintering temperature; Make ceramic sintered compact, be cooled to normal temperature with stove then.Temperature curve is:
From room temperature to 400 ℃, 2 hours heating-up times;
Be incubated binder removals 6 hours at 400 ℃;
From 400 ℃ to 1000 ℃, 15 hours heating-up times;
From 1000 ℃ to 1100 ℃, 3 hours heating-up times;
From 1100 ℃ to 1200 ℃, 3 hours heating-up times;
1200 ℃ of insulations 4.5 hours;
Cool to normal temperature with the furnace.
In suitability for industrialized production, only need be according to technological process of the present invention, the expansion of preparation equipment scale gets final product.Its core technology is two-step sintering technology and sintering schedule.
According to the inventive method the sample that each test prepares low residual voltage ZnO varistor is carried out each item performance test.Its leakage current is inhibited, less than 1uA/cm
2, non linear coefficient is greater than 40, and residual voltage ratio is less than 1.5.Its performance has tentatively reached the commercial Application requirement.
This technological effect is as shown in Figure 1, and a is the normalization J-E curve that adds 0.005mol%Al ionic weight piezo-resistance sample on the traditional handicraft basis, and b is the normalization J-E/E that adds 0.25mol%Al ionic weight piezo-resistance sample on the traditional handicraft basis
1mACurve, c adds the electric field strength curve and current density (J-E) curve (Fig. 1 (the A)) J-E/E of 0.25mol%Al ionic weight piezo-resistance sample for adopting two-step sintering seed crystal method preparation (instance one)
1mACurve (Fig. 1 (B)), curve can find that the voltage gradient difference of sample of a, b and three kinds of technologies of c and formulation is little from Fig. 1 (A).Normalized curve can find that the leakage current of c sample is similar with a sample from Fig. 1 (B), all at 1 μ A/cm
2Below, and b sample leakage current obviously descends.The residual voltage ratio aspect finds that relatively the c sample is obviously all low than a and b, has reached 1.47.Therefore can prove that two-step sintering seed crystal method is prepared in can reach the reduction residual voltage after adding more a large amount of Al ions, suppresses the effect of leakage current.
Claims (1)
1. process for preparing low residual voltage ZnO varistor ceramic; It is characterized in that; This method is based on the preparation technology of the low residual voltage ZnO varistor ceramic of two-step sintering method and seed crystal method, and this preparation method's composition of raw materials comprises: ZnO92.7-97mol%, Bi
2O
30.4-0.9mol%, MnO
20.4-0.7mol%, Sb
2O
30.5-1.5mol%, Co
2O
30.5-1.5mol%, SiO
20.8-1.7mol%, Al (NO
3)
39H
2O 0.1-0.4mol% and Cr
2O
30.3-0.7mol%; This method may further comprise the steps:
1) preparation of seed crystal and first step sintering:
(11) adopt the ZnO of the 20%-50% of total amount in the composition of raw materials, the Bi of 0%-20%
2O
3With whole Al (NO
3)
39H
2O; Place the ball grinder that is added with deionized water or alcohol, ball milling 8-12 hour, dry then as seed material;
(12) the dried seed material of ball milling is put into high-temperature electric resistance furnace, under 1200-1350 ℃, carry out first step pre-burning and became the seed crystal lump in 3-6 hour, cool to normal temperature with the furnace;
(13) with after the pulverizing of the seed crystal lump after the sintering, place ball grinder, add deionized water or alcohol ball milling 4-8 hour; Chose the seed crystal of 200-500 mesh sieve then, obtaining particle diameter is the seed crystal below the 75 μ m;
2) raw materials mix and the second step sintering
(21) seed crystal that all remaining raw materials, step 13) is obtained and mix according to 5% (wt) PVA solution that every gram raw material adds 0.5mL; In ball grinder, added the deionized water ball milling 8-12 hour; Dry, cross 70-150 purpose sieve then; The method of pressure forming is adopted in moisture granulation then, and it is pressed into base substrate;
(22) base substrate is carried out the second step sintering in airtight high-temperature electric resistance furnace, be warming up to holding temperature, be incubated 4-6 hour and carry out binder removal from room temperature; And then process was warming up to sintering temperature in 18-23 hour; Insulation is 3-6 hour under sintering temperature, makes ceramic sintered compact, is cooled to normal temperature with stove then.
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|---|---|---|---|
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