CN1587194A - Low loss and temperature coefficient and high magnetic conductivity ferrite material and its preparing method - Google Patents

Abstract

The present invention discloses one kind of ferrite material with low temperature coefficient, low loss and high magnetic conductivity and its preparation process. It is mainly spinel type structure and consists of Fe2O3 43-52 mol%, ZnO 28-42 mol%, CuO 3-12 mol% and NiO 5-12 mol%. The preparation process includes the following steps: mixing material; pre-sintering; adding impurity; secondary ball milling; forming and sintering. The NiZn ferrite material has homogeneous crystal grain size, clear crystal interface, integral crystal grain, compact structure and no holes. The ferrite material has CuO to replace NiO and lower pre-sintering temperature and sintering temperature and thus low power consumption, low requirement in sintering apparatus and low production cost; relatively wide pre-sintering temperature range and sintering temperature range, no need of protecting atmosphere, high technological repeatability and product consistency.

Description

Low-loss, low-temperature coefficient and high magnetic conductivity ferrite material and preparation method thereof

Technical field

The present invention relates to a kind of low-loss, low-temperature coefficient and high magnetic conductivity ferrite material and preparation method thereof.

Background technology

High magnetic permeability NiZn material is the main raw material(s) of preparation rf broadband device.And the rf broadband device TV, communication, radar, instrument and automatically aspect such as control application very generally.And, needing a large amount of novel rf broadband components and parts along with the continuous development of these technology, digital TV network system is replacing original jeep rapidly especially now, and the transformation of this network system needs a large amount of rf broadband components and parts.This provides a very big market for the rf broadband components and parts.And an important development direction of rf broadband device is exactly to have wideer operating frequency and can adapt to different Working environments, particularly can both work normally under different temperature.This development trend has proposed higher performance requriements to existing high magnetic permeability NiZn ferrite.Require the NiZn ferrite to have higher magnetic permeability, lower loss and better temperature factor.Therefore initial permeability is greater than 1500, and the height with wideer operating temperature range is led the ferritic market requirement of NiZn and just constantly enlarged.

The still conventional ceramic technique current, that preparation high magnetic permeability NiZn ferrite mainly adopts, calcined temperature generally is controlled at about 1000 ℃, and sintering temperature can be about 1200 ℃.Under so high sintering temperature, the easy generation of crystal grain is grown up unusually, and it is inhomogeneous that crystal grain becomes, and causes the deterioration of loss and temperature factor; And so high sintering temperature manufactures and designs the requirement height to sintering oven, and energy consumption is big, is unfavorable for environmental protection and reduces cost.And because the calcined temperature height, it is big that the hardness of pre-imitation frosted glass becomes, and makes that pre-imitation frosted glass is difficult for pulverizing in the secondary breaking process, increased the loss of the steel ball in mechanical milling process, brings a large amount of impurity easily into.

In order to reduce pre-burning and sintering temperature, overcome these shortcomings of existing technology, improve the performance of material, the measure of mainly taking at present mainly contains following a few class:

1. invent new preparation method and replace original conventional ceramic technique.For example coprecipitation method, sol-gel method, sol-gel self-propagating combustion, hydrothermal method and spread method etc. certainly.Though these methods all each have its characteristics, also overcome some defectives of conventional ceramic technique to a certain extent, aspect cost and technology stable, compare with conventional ceramic technique, still exist many deficiencies, technology is not mature enough, is left to be desired.

2. interpolation fusing assistant.Usually add Bi in process of production ₂O ₃Or V ₂O ₅As fusing assistant, but the method for taking single fusing assistant to add, for reducing sintering temperature effect and not obvious, and along with the interpolation of fusing assistant, the loss of material increases, and makes the degradation of product.

3. adjusting process, the refinement powder.The mean particle size of powder is reduced to Nano grade, increased the particulate specific surface area, improved the activity of powder, but the simple granularity that reduces will propose higher requirement to equipment, be unfavorable for the decline of cost, and reducing granularity by adjusting process also has certain limit merely, can not be unlimited reduce granularity, after granularity drops to a certain degree, easy long-living reunion.

Therefore, adopt conventional ceramic technique,, take multiple fusing assistant to unite to add and existing oxide process parameter is improved by adjusting the main formula of NiZn material, reducing pre-burning and sintering temperature is to reduce cost, and improves the feasible method of the performance of NiZn Ferrite Material.

Summary of the invention

The purpose of this invention is to provide a kind of low-loss, low-temperature coefficient and high magnetic conductivity ferrite material and preparation method thereof.

Low-loss, low-temperature coefficient and high magnetic conductivity ferrite material, its principal phase are spinel structure, with consisting of of composition calculated by content of oxides:

Fe ₂O ₃Be 43～52mol%;

ZnO is 28～42mol%;

CuO is 3～12mol%;

NiO is 5～12mol%.

The step of low-loss, low-temperature coefficient and high magnetic conductivity ferrite material preparation method is:

1) starting material mix:

Choose 43～52mol%Fe ₂O ₃, 28～42mol%ZnO, 3～12mol%CuO and 5～12mol%NiO be as starting material, puts into ball mill, the deionized water of weight such as adding, ball milling 5～9 hours;

2) pre-burning:

The stove pre-burning is put in the material oven dry that mix grinding is good, and calcined temperature is 740～800 ℃, and the pre-burning time is 1～4h;

3) impurity adds:

Select Bi for use ₂O ₃And V ₂O ₅Nano powder is as additive, wherein Bi ₂O ₃Percentage composition be:

0.01wt%～0.5wt%, and V ₂O ₅Percentage composition be: 0.01wt%～0.4wt%, Bi ₂O ₃And V ₂O ₅Weight percent be: 1: 1.2～1.4;

4) secondary ball milling:

Material is put into ball mill, the deionized water of weight such as adding, ball milling 3～10 hours, the mean particle size that makes pre-imitation frosted glass is less than 0.8 μ m;

5) forming and sintering:

With the slurry oven dry, add the polyvinyl alcohol (PVA) of 8～15wt%, the stove sintering is put in compression moulding.Sintering temperature is 950～1000 ℃, and sintering time is to get final product in 6～8 hours.

Advantage of the present invention:

The NiZn Ferrite Material even grain size of the present invention's preparation, crystal boundary is clear, and crystal grain is complete, does not have hole, dense structure.Grain-size is in 3～5 mu m ranges.. the present invention uses CuO to substitute NiO, and pre-burning and sintering temperature are very low, and the energy consumption in the preparation process is littler, owing to have very low pre-burning and sintering temperature, therefore also lower to the design requirements of equipment, reduced production cost.Owing to have the pre-burning and the sintering range of broad, and need not atmosphere protection, make process repeatability and consistency of product all fine.

Description of drawings

Fig. 1 is the XRD figure spectrum of pre-imitation frosted glass;

Fig. 2 is the XRD figure spectrum of embodiment 1 sintered sample;

Fig. 3 is the stereoscan photograph of sintered sample.

Embodiment

The invention provides a kind of low-loss, low-temperature coefficient and high magnetic conductivity ferrite material and preparation method thereof.Add and processing parameter by adjusting component prescription and impurity, pre-burning and sintering temperature have been reduced, make calcined temperature be lower than 800 ℃, sintering temperature is lower than 1000 ℃, improved the ferritic performance of NiZn, especially temperature profile makes the ratio temperature factor of NiZn Ferrite Material in 20～65 ℃ temperature range of preparing less than 3.0 * 10 ^-6, initial permeability is 1500, the specific loss coefficient under the test condition of 100kHz and 0.25mT is less than 10.0 * 10 ^-6, the specific loss coefficient under the test condition of 500kHz and 0.25mT is less than 45.0 * 10 ^-6

The above-mentioned ratio temperature factor in 20～65 ℃ temperature range is less than 3.0 * 10 ^-6, initial permeability is only to have the spinel phase in 1500 the NiZn Ferrite Material, does not have other dephasigns, grain-size is in 3～5 mu m ranges.

Starting material are selected commercially pure Fe ₂O ₃, ZnO, NiO and CuO.Take by weighing various starting material according to the component molecules formula and carry out mix grinding, mix grinding equipment choosing rotary mill.In the mix grinding process, the deionized water of weight such as adding, ball milling 5～9h makes starting material mix.

Temperature range during pre-burning is 740～800 ℃ because main formula is a rich Cu prescription, CuO can with Fe ₂O ₃Near 700 ℃, form CuFe ₂O ₄, make ferrospinel to form in very low temperature, this is very favorable for the follow-up sintering reaction of promotion, and effectively reduces sintering temperature.

Bi ₂O ₃And V ₂O ₅Unite and add as adding impurity.The mode that adopts single fusing assistant to add, though reduction sintering temperature that can be to a certain degree, effect still is not ideal enough, and along with the increasing of addition, makes ferritic quality factor descend.Adopt an amount of V ₂O ₅As fusing assistant,, reduced the quality factor of low-frequency range though can improve high frequency characteristics; And an amount of Bi ₂O ₃Interpolation then opposite, favourable to reducing the low-frequency range loss, and unfavorable for reducing the high band loss.Therefore adopt Bi ₂O ₃And V ₂O ₅The associating interpolation is as fusing assistant, wherein Bi ₂O ₃And V ₂O ₅Weight percent be: 1: 1.2～1.4, can effectively reduce sintering temperature, make sintering temperature be reduced to below 1000 ℃, and the high and low frequency loss all obtained very big improvement, have frequency response characteristic preferably.

Pre-imitation frosted glass is carried out secondary ball milling, require particulate mean particle size behind the ball milling, increased the specific surface area of particulate material, improved the reactive behavior of powder greatly, further reduced sintering temperature less than 0.8 μ m.

Cu ²⁺Bohr's magnetic moment less than Ni ²⁺, Cu ion substitution Ni ion will reduce the specific saturation magnetization of material, and

Therefore the Cu ionic substitutes and will have a negative impact to magnetic permeability, can improve the interior magnetic moment M of unit volume but the low-temperature sintering body has higher density _s, and the more uniform crystal grain of complete sum more helps moving of domain wall, this also is very favorable for improving magnetic permeability, therefore can effectively reduce this disadvantageous effect, thereby guarantees that the low-temperature sintering body has high initial permeability.

High density and crystal grain distribution uniformly are that the low-temperature sintering body has more low-loss major cause.Because in the range of frequency below 1MHz, the ferritic loss of NiZn mainly is to be made of magnetic hysteresis loss, and its magnetized mechanism mainly is that domain wall moves.And higher sintered density and more uniform grain-size will help moving of domain wall, reduce magnetic hysteresis loss.

On the other hand, the Cu ion substitution Ni ion, occupied octagonal site, and Cu ²⁺Ratio of ionic radii Ni ²⁺Bigger, so ferritic unit cell dimension of low-temperature sintering NiZn and the increase of oxygen parameter.

And:

$d_{\mathrm{AX}}=(u-\frac{1}{4})a\sqrt{3}---\left(1\right)$

$d_{\mathrm{BX}}=(\frac{5}{8}-u)a---\left(2\right)$

Wherein, u is the oxygen parameter; A is a unit cell dimension; d _AXBe to occupy the metal ion of tetragonal site (A position) and the bond distance between the oxonium ion in the spinel structure; d _BXBe to occupy the metal ion of octagonal site (B position) and the bond distance between the oxonium ion in the spinel structure.

Can see from equation (1) and (2), along with the increase of oxygen parameters u, d _AXIncrease d _BXReduce.This explanation, behind Cu ion substitution Ni ion, the oxygen parameters u increases, make the Zn ion and the bond distance between the oxonium ion that have occupied tetragonal site increase, occupy reduced then corresponding with the bond distance between the oxonium ion of metal ion of octagonal site, this has strengthened metal ion in the octahedron and the exchange-coupling interaction between the oxonium ion.

Because non magnetic ion Zn ²⁺Occupied the A position in the spinel structure, most magnetic ion has then occupied the B position, therefore the ferritic magnetic of NiZn is mainly derived from magnetic ion in the B position and the spin-exchange-coupled between the O ion, and the Cu ion enters magnetic ion and the O ionic exchange-coupling interaction of having strengthened in the lattice in the B position, make exchange-coupling interaction heat resistanceheat resistant interference performance strengthen, thereby material has better thermostability, and microstructure can effectively reduce inner demagnetizing field uniformly, and this also is another important factor of improving temperature profile.

Ratio temperature factor in 20～65 ℃ temperature range provided by the invention is less than 3.0 * 10 ^-6, initial permeability is that 1500 NiZn Ferrite Material and preparation process specify as follows:

1. raw-material selection and main formula design: the starting material of low sintering NiZn Ferrite Material provided by the invention are selected commercially pure Fe ₂O ₃, ZnO, NiO and CuO.The main composition and the content of Ferrite Material are calculated as with oxide compound: Fe ₂O ₃Be that 43～52mol%, ZnO are that 28～42mol%, CuO are 3～12mol%, NiO is 5～12mol%.

2. raw-material mixing: take by weighing each starting material by main formula, put into ball mill, the deionized water of weight such as adding, ball milling 5～9 hours.

3. pre-burning: the starting material oven dry that mix grinding is good, put into the stove pre-burning.Calcined temperature is 740～800 ℃, and the pre-burning time is 1～4h, and atmosphere is air, furnace cooling after the pre-burning.After the pre-burning, require the starting material total overall reaction, have only spinel structure in the pre-imitation frosted glass, do not have other dephasigns.

4. impurity adds: select Bi ₂O ₃And V ₂O ₅Unite and add as adding impurity.Bi wherein ₂O ₃Percentage composition be: 0.01～0.5wt%, and V ₂O ₅Percentage composition be: 0.01～0.4wt%.Require Bi ₂O ₃And V ₂O ₅Weight percent be: 1: 1.2～1.4.

5. secondary ball milling: pre-imitation frosted glass is put into ball mill, the deionized water of weight such as adding, ball milling 3～10h, the mean particle size that makes pre-imitation frosted glass is less than 0.8 μ m.

6. forming and sintering: with pre-imitation frosted glass oven dry, add the polyvinyl alcohol (PVA) of 8～15wt%, uniform mixing uses grinding tool compression moulding, puts into the stove sintering.Sintering temperature is 950～1000 ℃, and sintering time is 6～8h, and sintering atmosphere is an air, furnace cooling after sintering is finished.

NiZn Ferrite Material by the inventive method preparation can be implemented in sintering in 950 ℃～1000 ℃ scopes, and the ratio temperature factor in 20～65 ℃ temperature range is less than 3.0 * 10 ^-6, initial permeability is greater than 1500, and the specific loss coefficient under the test condition of 100kHz and 0.25mT is less than 10.0 * 10 ^-6, the specific loss coefficient under the test condition of 500kHz and 0.25mT is less than 45.0 * 10 ^-6Use in the NiZn ferrite of preparation method's preparation provided by the invention, because a large amount of CuO of employing substitute NiO, make raw-material cost greatly descend, and the pre-imitation frosted glass of preparing is because active fine, reduced sintering temperature greatly, saved energy consumption, this also reduces the cost of product greatly.The wide temperature of preparing at last, low-loss, initial permeability are the good starting material of preparation broadband radio-frequency devices greater than 1500 NiZn Ferrite Material.

Embodiment 1:

1) raw-material selection: the starting material of low sintering NiZn Ferrite Material provided by the invention are selected commercially pure Fe ₂O ₃, ZnO, NiO and CuO.

2) composition design and weighing: according to Fe ₂O ₃For 49mol%, ZnO are that 32mol%, CuO are 10mol%, NiO is the Fe that 9mol% takes by weighing corresponding weight ₂O ₃, ZnO, CuO and NiO.

3) raw-material mixing: the starting material that weigh up are put into ball mill, the deionized water of weight such as adding, ball milling 5 hours.

4) pre-burning: the starting material oven dry that mix grinding is good, put into the stove pre-burning.Calcined temperature is 780 ℃, and the pre-burning time is 2h, and atmosphere is air, furnace cooling after the pre-burning.After the pre-burning, pre-imitation frosted glass is carried out the XRD facies analysis, determine only to have spinel structure in the pre-imitation frosted glass, do not have other dephasigns.

5) impurity adds: select Bi ₂O ₃And V ₂O ₅Unite and add as adding impurity.Bi wherein ₂O ₃Percentage composition be: 0.15wt%, and V ₂O ₅Percentage composition be: 0.20wt%, Bi ₂O ₃And V ₂O ₅Weight percent be: 1: 1.33.

6) secondary ball milling: pre-imitation frosted glass is put into ball mill, the deionized water of weight such as adding, ball milling 8h, the mean particle size that makes pre-imitation frosted glass is less than 0.8 μ m.

7) forming and sintering: with pre-imitation frosted glass oven dry, the polyvinyl alcohol (PVA) that adds 10wt%, uniform mixing, use thorough mixing, use 45 order sub-sieve granulations, and be pressed into φ 20 sample rings, put into the box-type furnace sintering, sintering temperature is controlled to be about 955 ℃, and soaking time is 6h, and furnace cooling is to room temperature.

The magnetism testing of the sample ring for preparing carries out on the Hp4284A electric impedance analyzer, and the density of sample adopts buoyancy method to measure.Use X-ray diffraction analysis instrument (XRD) sample to be carried out mutually and microstructure analysis with scanning electron microscope (SEM).

The magnetic property of sample and density measurement result such as following table are said and are shown:

Table 1: the magnetic property of sintered sample and the test result of density:

Numbering	Density (kg/m 3)	Initial permeability (test frequency: 10kHz)	Than temperature factor (20～65 ℃)	Specific loss coefficient (tan δ/μ i)
						????100kHz	???500kHz
				Sample 1	???5.11			??????1522	?????1.9×10 -6	????8.4×10 -6	???33.5×10 -6

The pre-imitation frosted glass of sample and the XRD figure of sintered compact spectrum are seen accompanying drawing 1 and accompanying drawing 2.As we can see from the figure, in pre-imitation frosted glass and sintered compact, only there is the spinel structure crystal, do not have other dephasigns.

The visible accompanying drawing 3 of the microstructure analysis of sample.Can see that from the SEM photo of sintered sample the crystal boundary of the NiZn Ferrite Material of preparation method's preparation provided by the invention is clear, uniform crystal particles, crystal grain is complete, does not have hole, dense structure, grain-size is 3～5 μ m.

Embodiment 2:

1) selection of material: the starting material of low sintering NiZn Ferrite Material provided by the invention are selected commercially pure Fe ₂O ₃, ZnO, NiO and CuO.

2) composition design and weighing: according to Fe ₂O ₃For 44mol%, ZnO are that 29mol%, CuO are 12mol%, NiO is the Fe that 5mol% takes by weighing corresponding weight ₂O ₃, ZnO, CuO and NiO.

3) raw-material mixing: the starting material that weigh up are put into ball mill, the deionized water of weight such as adding, ball milling 5 hours.

4) pre-burning: the starting material oven dry that mix grinding is good, put into the stove pre-burning.Calcined temperature is 740 ℃, and the pre-burning time is 2h, and atmosphere is air, furnace cooling after the pre-burning.After the pre-burning, pre-imitation frosted glass is carried out the XRD facies analysis, determine only to have spinel structure in the pre-imitation frosted glass, do not have other dephasigns.

5) impurity adds: select Bi ₂O ₃And V ₂O ₅As uniting interpolation impurity.Bi wherein ₂O ₃Percentage composition be: 0.12wt%, and V ₂O ₅Percentage composition be: 0.16wt%, Bi ₂O ₃And V ₂O ₅Weight percent be: 1: 1.33.

6) secondary ball milling: pre-imitation frosted glass is put into ball mill, the deionized water of weight such as adding, ball milling 6h, the mean particle size that makes pre-imitation frosted glass is less than 0.8 μ m.

7) forming and sintering: with pre-imitation frosted glass oven dry, the polyvinyl alcohol (PVA) that adds 10wt%, uniform mixing, use thorough mixing, use 45 order sub-sieve granulations, and be pressed into φ 20 sample rings, put into the box-type furnace sintering, sintering temperature is controlled to be about 950 ℃, and soaking time is 6h, and furnace cooling is to room temperature.

The magnetism testing of the sample ring for preparing carries out on the Hp4284A electric impedance analyzer, and the density of sample adopts buoyancy method to measure.

The magnetic property of sample and density measurement result such as following table are said and are shown:

Table 2: the magnetic property of sintered sample and the test result of density:

Numbering	Density (kg/m 3)	Initial permeability (test frequency: 10kHz)	Than temperature factor (20～65 ℃)	Specific loss coefficient (tan δ/μ i)
						????100kHz	??500kHz
				Sample 1	????5.12			??????1507	???2.7×10 -6	????9.3×10 -6	??40.4×10 -6

Increase the content of CuO, can reduce pre-burning and sintering temperature and reduce Bi ₂O ₃And V ₂O ₅Addition, so the time of secondary ball milling also can reduce accordingly, but temperature factor and loss have been risen.

Embodiment 3:

1) selection of material: the starting material of low sintering NiZn Ferrite Material provided by the invention are selected commercially pure Fe ₂O ₃, ZnO, NiO and CuO.

2) composition design and weighing: according to Fe ₂O ₃For 52mol%, ZnO are that 36mol%, CuO are 3mol%, NiO is the Fe that 12mol% takes by weighing corresponding weight ₂O ₃, ZnO, CuO and NiO.

2) raw-material mixing: the starting material that weigh up are put into ball mill, the deionized water of weight such as adding, ball milling 5 hours.

4) pre-burning: the starting material oven dry that mix grinding is good, put into the stove pre-burning.Calcined temperature is 800 ℃, and the pre-burning time is 2h, and atmosphere is air, furnace cooling after the pre-burning.After the pre-burning, pre-imitation frosted glass is carried out the XRD facies analysis, determine only to have spinel structure in the pre-imitation frosted glass, do not have other dephasigns.

5) impurity adds: select Bi ₂O ₃And V ₂O ₅Unite and add as adding impurity.Bi wherein ₂O ₃Percentage composition be: 0.20wt%, and V ₂O ₅Percentage composition be: 0.28wt%, Bi ₂O ₃And V ₂O ₅Weight percent be: 1: 1.4.

6) secondary ball milling: pre-imitation frosted glass is put into ball mill, the deionized water of weight such as adding, ball milling 10h, the mean particle size that makes pre-imitation frosted glass is less than 0.8 μ m.

7) forming and sintering: with pre-imitation frosted glass oven dry, the polyvinyl alcohol (PVA) that adds 10wt%, uniform mixing, use thorough mixing, use 45 order sub-sieve granulations, and be pressed into φ 20 sample rings, put into the box-type furnace sintering, sintering temperature is controlled to be about 995 ℃, and soaking time is 6h, and furnace cooling is to room temperature.

The magnetism testing of the sample ring for preparing carries out on the Hp4284A electric impedance analyzer, and the density of sample adopts buoyancy method to measure.

The magnetic property of sample and density measurement result such as following table are said and are shown:

Table 3: the magnetic property of sintered sample and the test result of density:

Numbering	Density (kg/m 3)	Initial permeability (test frequency: 10kHz)	Than temperature factor (20～65 ℃)	Specific loss coefficient (tan δ/μ i)
						???100kHz	??500kHz
				Sample 1	???5.08			????1531	????2.9×10 -6	???9.8×10 -6	??43.4×10 -6

Along with the minimizing of the content of Cu, need more Bi ₂O ₃And V ₂O ₅Addition and pre-burning and the sintering temperature of Geng Gao, so the time of secondary ball milling must corresponding prolong, and density reduced, initial permeability also descends accordingly, loss also will be risen, temperature factor has also raise.

Claims (2)

1. a low-loss, low-temperature coefficient and high magnetic conductivity ferrite material, it is characterized in that: its principal phase is a spinel structure, with consisting of of composition calculated by content of oxides:

Fe ₂O ₃Be 43～52mol%;

ZnO is 28～42mol%;

CuO is 3～12mol%;

NiO is 5～12mol%.

2. a low-loss, low-temperature coefficient and high magnetic conductivity ferrite material preparation method is characterized in that the step of method is:

1) starting material mix:

Choose 43～52mol%Fe ₂O ₃, 28～42mol%ZnO, 3～12mol%CuO and 5～12mol%NiO be as starting material, puts into ball mill, the deionized water of weight such as adding, ball milling 5～9 hours;

2) pre-burning:

The stove pre-burning is put in the material oven dry that mix grinding is good, and calcined temperature is 740～800 ℃, and the pre-burning time is 1～4h;

3) impurity adds:

Select Bi for use ₂O ₃And V ₂O ₅Nano powder is as additive, wherein Bi ₂O ₃Percentage composition be:

0.01wt%～0.5wt%, and V ₂O ₅Percentage composition be: 0.01wt%～0.4wt%, Bi ₂O ₃And V ₂O ₅Weight percent be: 1: 1.2～1.4;

4) secondary ball milling:

Material is put into ball mill, the deionized water of weight such as adding, ball milling 3～10 hours, the mean particle size that makes pre-imitation frosted glass is less than 0.8 μ m;

5) forming and sintering:

With the slurry oven dry, add the polyvinyl alcohol (PVA) of 8～15wt%, the stove sintering is put in compression moulding.Sintering temperature is 950～1000 ℃, and sintering time is to get final product in 6～8 hours.

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