A kind of preparation method of aluminum oxide polycrystal material piece
Technical field
The present invention relates to a kind of preparation method of aluminum oxide polycrystal material piece, belong to special cermacis fabricating technology field.
Background technology
White light emitting diode (LED) is since realizing commercialization, and is pollution-free with it, volume is little, low in energy consumption and reliability advantages of higher, is just starting the another field lighting source revolution continue incandescent light, luminescent lamp after on the illumination history.1991, the appearance of the basic blue-ray LED of gan (GaN) was opened up new way for realization LED white-light illuminating again.According to the principle of three primary colours, with blue light that GaN sent out with can be by blue-light excited and the fluorescent material emission gold-tinted makes up, both stacks can form white light, thereby realize white-light illuminating.Therefore GaN base LED has also obtained developing rapidly, becomes the light-emitting semiconducting material that is most widely used.
At present, GaN sill and the device for LED mainly is to obtain in the mode that substrate grows epitaxial film by thin-film technique.Its used substrate material comprises sapphire (α-Al
2O
3), SiC, Si, ZnO and GaN etc., but have only sapphire and these two kinds of substrates of SiC to obtain fairly large commercial applications up to now, wherein being most widely used with Sapphire Substrate again.This is because sapphire has many advantages as substrate material: manufacturing technology is ripe relatively, moderate cost; The chemical stability height can be used in the high temperature epitaxy process of growth; The physical strength height is easy to handle and clean, and is good to the light transmission of visible light.Therefore, most of thin film epitaxial growth technologies generally all with sapphire as substrate.
For being used for the epitaxially grown substrate level sapphire crystal of GaN, usually with the basic raw material of high purity aluminium oxide biscuit (its purity generally will reach the 5N level, namely 99.999%) as growing sapphire.Why directly do not adopt powder raw material, the one, because fluffy powder is too low to the filling ratio of the used crucible of growing sapphire monocrystalline, single furnace output is little, influences production efficiency and cost; The 2nd, powder raw material easily flies upward, and is unfavorable to the high vacuum system of single crystal growing furnace.Therefore before growing sapphire crystal, need earlier alumina powder to be suppressed and sintered into block material.Along with LED illumination becomes the energy-conservation project that various countries advocate energetically and give special assistance to, also grow at top speed as the demand of the sapphire single-crystal of its upstream.Sapphire growth constantly strides forward towards the large size direction, and single crystal specification is from initial 20kg, 30kg, to 60kg, 80kg and even the above super large crystal development of 100kg.Under this overall background, each sapphire manufacturer is more strong to the demand of high density aluminum oxide biscuit.Because the density of used aluminum oxide biscuit is more big, just mean the peak filling rate more big (being to insert more raw materials in the unidimensional crucible) to crucible, under the condition that does not change the original configuration of single crystal growing furnace, just can grow single bigger crystal, corresponding production efficiency is higher, cost is lower, size and the yield rate of one-piece substrate have also been increased simultaneously, thereby in future market competition, obtain price advantage, take the good opportunity.
Yet homemade aluminum oxide polycrystal cake piece material normally adopts steel die to make in dry-pressing formed mode now, and burning till density, not high (density is 3.2 ~ 3.6 g/cm
3, have only a-Al
2O
380% ~ 90% of theoretical density is usually about 85%).Adopt the a-Al of such density
2O
3The polycrystalline cake piece material sapphire single-crystal of growing only has about 60% a peak filling rate of crucible, and usage ratio of equipment is obviously not enough, makes production cost improve.In addition, such biscuit also exists such as overall dimension and limit by mould, and pressing process is easily introduced secondary pollution problems such as (main from the Fe in the mould, Cr element), and product purity does not generally all reach 5N, and finally influences the quality of sapphire crystal.On the other hand, used a-Al in the biscuit moulding process
2O
3The size of powder also affects density and the formability of aluminum oxide biscuit.With present both at home and abroad preparation 5N grade aluminum oxide powder main stream approach---alkoxide hydrolysis is example, though the powder purity that makes with this method can reach 99.999%, can satisfy the long brilliant requirement of high quality substrate level sapphire fully, but the aluminium alcoholates method is by Al (OH) at last
3Change a-Al into through high-temperature calcination
2O
3, the a-Al of gained
2O
3Powder granule is big (micron order), and the intergranular space is many, is difficult for tamping mould, and the biscuit density after the moulding is little.And because bonding force is little between its particle, in the condition compacted under difficulty of adding additives not, green strength is low, and is easily cracked, especially is difficult to obtain large-sized product.If be processed into thinner powder, then when increasing production cost, also will face powder a series of problems such as contaminated in the course of processing, and finally influence quality and the density of cake piece material.
In sum, for improving the quality of aluminum oxide cake piece material density and assurance product, the particle diameter of used alumina powder is selected, and it is imperative to improve existing biscuit moulding process.
Summary of the invention
Defective at the prior art existence, the object of the present invention is to provide a kind of preparation method of aluminum oxide polycrystal material piece, can improve existing aluminum oxide cake piece material density, to improve sapphire production efficiency, reduce production costs, avoid in the biscuit production process, taking place problems such as material powder secondary pollution, biscuit blank cracking simultaneously.
The present invention conceives as follows:
For obtaining above-mentioned a-Al
2O
3Polycrystalline piece material is at first by calculating the shared quantitative proportion relation when of determining size between used powder raw material particle.Elder generation as the main body particle, regards this powder as diameter for the spheroid of its median size and simple cube of work, body-centered cubic or face-centered cubic close-packed with a kind of powder with greater particle size during calculating, draws the voidage of existence; Calculate overall dimension and the relative populations (as shown in Figure 1-Figure 3) of inserting the required another kind of or two kinds of calking powders (also representing with spheroid) in this Mi Dui space again.Consider that this model is the theoretical closest packing situation under the perfect condition, actually operating medium silt mode is fully like this arranged, and any powder itself all has certain particle and distributes, and therefore according to experiment gained result the above-mentioned theory value has been carried out certain correction.
For achieving the above object, according to above inventive concept, the present invention adopts following technical scheme:
A kind of preparation method of aluminum oxide polycrystal material piece has following technological process and step:
A. with two or three 99.999% the commercial high-purity a-Al that uses that the aluminium alcoholates method produces
2O
3Powder is starting raw material, and when adopting two kinds of particle diameter powder proportionings, main body particle powder is 1:0.1 ~ 1:0.2 with the ratio of the median size of calking particle powder, and mass ratio is between 1:0.08 ~ 1:0.15; When adopting three kinds of particle diameter powder proportionings, the ratio of the median size of three kinds of particle powders is 1:(0.6 ~ 0.7): (0.2 ~ 0.25), weight ratio are 1:(0.3 ~ 0.4): (0.05 ~ 0.06);
B. the powder with above-mentioned different-grain diameter successively alternately is packed in the rubber tubbiness mould of homemade different diameter size, and rubber mold places on the shaking table in reinforced process all the time, and applies the vibration that the vertical direction frequency is 500 ~ 1000 Hz;
C. the rubber mold after will loading is placed in the cold isostatic press through sealing, and pressurize is 1 ~ 5 minute under 100 ~ 200 MPa pressure, makes cylindric biscuit after the demoulding;
D. cylindric biscuit is carried out sintering under air or nitrogen or vacuum environment, sintering range is 1550 ~ 1750 ℃, and sintering time is 3 ~ 5 hours; The final relative density that obtains is greater than 90%, and density is greater than 3.6 g/cm
3A-Al
2O
3Polycrystalline piece material.
Compared with prior art, the present invention has following outstanding substantive distinguishing features and progressive significantly:
The present invention proposes the a-Al with two or three granularity
2O
3Particle mixes and realizes the closeizationest accumulation by certain proportioning of optimizing, again in conjunction with cold isostatic compaction prepared high-density a-Al
2O
3The method of polycrystalline piece material.At the a-Al that adopts aforesaid method to make
2O
3In the polycrystalline piece material, the small particle size powder can be filled up the space between the large-size particle, contact is more between powder, it is bigger to interact, thereby in compression moulding and high-temperature sintering process, be difficult for chipping, be easy to obtain large-sized product, and its to burn till the relative commercial alumina cake of density piece material higher.Adopt isostatic cool pressing technology that above-mentioned mixed powder is pressed into block material, equipment used is cold isostatic press, and mould is rubber mold, a-Al
2O
3The polycrystal piece in whole preparation production process not with any metallic contact, avoid the generation of secondary pollution.
Description of drawings
Fig. 1 is the multistage granularity particle of simple cubic close-packed model.
Fig. 2 is the multistage granularity particle of face-centered cubic close-packed model.
Fig. 3 is the multistage granularity particle of body-centered cubic close-packed model.
Embodiment
After now specific embodiments of the invention being described in.
Embodiment 1
Process and the step of present embodiment are described below:
1. adopt the commercial high-purity 5N(99.999% of aluminium alcoholates method of two kinds of different-grain diameters) a-Al
2O
3Powder is raw material, and the ratio of median size is got 1:0.15, and weight ratio is got 1:0.1.Be specially the big particle diameter powder of 50 μ m and get 2400 g, 7.5 μ m small particle size powders are got 240 g, gross weight 2640 g.The theoretical porosity that calculates according to close heap model is 25.56%.
2. above-mentioned powder is waited quality ground to be divided into 4 parts respectively, successively alternately being packed into homemade diameter is 150 mm, in the rubber tubbiness mould of high 130 mm.Rubber mold places on the shaking table in reinforced process all the time, and applies the vibration that the vertical direction frequency is 500 Hz;
3. the rubber mold after the filling is placed in the isostatic pressing machine through sealing, and pressurize is 3 minutes under 200 MPa pressure, makes cylindric biscuit after the demoulding;
4. cylindric biscuit carries out sintering under air ambient, and sintering temperature is 1650 ℃, and sintering time is 5 hours.Final acquisition diameter is 113 mm, high 72 mm, and density is 3.67 g/cm
3A-Al
2O
3Polycrystalline piece material.The sample good moldability, the surface does not have cracking, and relative density is 92%.
Embodiment 2
The purity of the used powder raw material of present embodiment, a-Al
2O
3Identical among polycrystalline piece material drawing method and step and the embodiment 1.Difference has been to adopt the aluminium alcoholates method a-Al of three kinds of different-grain diameters
2O
3Powder is raw material, and median size is respectively 10 μ m, 7 μ m and 3 μ m(are that three's particle diameter ratio is 1:0.7:0.3), weight gets 1800 g, 720 g respectively and 108 g(are that three's weight ratio is 1:0.4:0.06), the total gross weight is 2628g.The theoretical porosity that calculates according to close heap model is 24.08%.
After tested, with method and step described in this embodiment, finally obtaining diameter is 114 mm, high 70 mm, and density is 3.69 g/cm
3A-Al
2O
3Polycrystalline piece material.The sample good moldability, the surface does not have cracking, and relative density reaches 93%.