CN112979282B - Alumina ceramic sintered body and preparation method and application thereof - Google Patents

Alumina ceramic sintered body and preparation method and application thereof Download PDF

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CN112979282B
CN112979282B CN201911216272.4A CN201911216272A CN112979282B CN 112979282 B CN112979282 B CN 112979282B CN 201911216272 A CN201911216272 A CN 201911216272A CN 112979282 B CN112979282 B CN 112979282B
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alumina
alumina ceramic
sintered body
ceramic sintered
cerium
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CN112979282A (en
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邱基华
黄雪云
江楠
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Chaozhou Three Circle Group Co Ltd
Nanchong Three Circle Electronics Co Ltd
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Chaozhou Three Circle Group Co Ltd
Nanchong Three Circle Electronics Co Ltd
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Abstract

The invention relates to an alumina ceramic sintered body, which comprises 85.6-95.2% by mass of alumina, a cerium-containing compound (calculated in the form of cerium oxide) and a niobium-containing compound (calculated in the form of niobium oxide), wherein the mass fraction of the cerium-containing compound (calculated in the form of cerium oxide) is higher than that of the niobium-containing compound (calculated in the form of niobium oxide). The invention uses high-purity alpha-Al2O3Particles as raw material, with Ce2O3And Nb2O5Is used as an additive, and the additive Ce is used in the sintering process2O3And Nb2O5Will generate CeNbO4As a liquid phase, the sintering temperature of the composite ceramic is obviously reduced, the interface reaction is promoted, and alumina crystal grains grow into a columnar shape in an anisotropic manner; the columnar crystal realizes the synergistic toughening of the composite ceramic mainly by deflecting the crack, pulling out the columnar crystal to absorb energy and the like, and reduces the expansion energy of the crack tip, so that the ceramic material has higher fracture toughness.

Description

Alumina ceramic sintered body and preparation method and application thereof
Technical Field
The invention relates to an alumina ceramic sintered body and a preparation method and application thereof, belonging to the technical field of alumina ceramics.
Background
Alumina ceramics have a series of excellent characteristics such as high strength, high hardness, high temperature resistance, wear resistance, corrosion resistance and the like, and the alumina ceramics are widely applied because of wide raw material sources and low manufacturing cost. However, after the alumina crystal grains are sintered at high temperature, the microstructure of the alumina crystal grains is isometric crystal, the size of the crystal grains is more than 5um, and the fracture toughness is low, and is usually only 3-4 MPa.m1 /2This drawback greatly limits the range of applications of alumina ceramics. Therefore, a large number of scholars at home and abroad invest in research to improve the toughness of the alumina ceramics.
At present, the toughening mechanism of the alumina ceramics mainly comprises phase change toughening, whisker or fiber toughening, in-situ toughening and the like, and corresponding research has made a certain progress.
(1) Toughening by phase change
The phase change toughening is to add certain additive into the alumina, wherein the additive undergoes phase change in the alumina sintering process to generate compressive stress on the alumina, so that the toughness of the alumina substrate is improved.
For example, the Chinese invention patent CN103496952A reports the addition of 20-30% zirconia, and CN102718470A proposes Zr (OH)4+Y(OH)3/Al2O3In the main burning process of the slurry, the zirconium oxide generates a martensite phase transformation to enhance the fracture toughness of the aluminum oxide.
The disadvantages are as follows: the cost of adding zirconia is too high, the addition amount is more, and the more so is the nano zirconia. In addition, although the phase change toughening can obviously improve the fracture toughness of the ceramic, the toughening effect of the ceramic is affected under high-temperature conditions, the conventional zirconia toughened ceramic is only widely applied at normal temperature or low temperature, and the realization difficulty of the reversible process is high.
(2) Toughening of whiskers or fibers
At present, the toughening mechanism of the alumina ceramics comprises whisker or fiber toughening, and mainly comprises adding whisker or fiber into alumina so as to improve the toughness of the alumina.
For example, patents CN106542839A and CN101948325A report that SiC whisker is used to toughen Al2O3The toughness of the ceramic is obviously improved.
The disadvantages are as follows: however, the toughening method always has the defects of difficult preparation of the whisker, complex dispersion process, high price, reduction of sintering densification rate and preparation process, and certain harm to human bodies.
(3) In situ toughening
The in-situ toughening is to induce partial isometric alumina crystals to grow into columns in an anisotropic way by adding additives or crystal seeds, so as to achieve the aim of toughening.
For example, Chinese patent CN101343176A reports a method for preparing self-reinforcing submicron crystal alumina ceramics in fine crystal alpha-Al2O3Adding additives, such as MgO, ZnO, CaO, Y2O3、La2O3And the like, and the length-diameter ratio of columnar crystals is more than 3.
The advantages are that: the method has the advantages that the additive can be uniformly distributed in the matrix, aggregation is not generated, and the sintering performance is good. In addition, the interface between the additive crystal grain and the matrix is clean, has few defects, is well combined with each other, and is particularly favorable for improving the high-temperature mechanical property of the material.
The disadvantages are as follows: the existing in-situ toughening research has limited improvement degree on the fracture toughness of the alumina ceramic, and columnar crystals are difficult to effectively control and influence other properties of the alumina ceramic inevitably.
Therefore, at the present stage, the most economical and reasonable method for toughening alumina ceramics still needs to find a proper sintering aid and a proper sintering method.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provides an alumina ceramic sintered body, a preparation method and application thereof, wherein Ce is used2O3And Nb2O5Is an additive, reduces the sintering temperature of the alumina ceramic, and realizes the synergistic effect of various toughening modes such as particle dispersion toughening, whisker toughening, phase change toughening and the like.
In order to achieve the purpose, the invention adopts the technical scheme that: an alumina ceramic sintered body comprising alumina in a mass fraction of 85.6 to 95.2%, a cerium-containing compound (calculated as cerium oxide) in a mass fraction higher than that of a niobium-containing compound (calculated as niobium oxide), and a niobium-containing compound (calculated as niobium oxide).
In a preferred embodiment of the alumina ceramic sintered body of the present invention, the ratio of the mass fraction of the cerium-containing compound (in the form of cerium oxide) to the mass fraction of the niobium-containing compound (in the form of niobium oxide) is (1.4 to 2.2): 1.
the additive of the alumina ceramic sintered body of the invention selects cerium oxide (Ce)2O3) And niobium oxide (Nb)2O5). Cerium niobate (CeNbO)4) Is a rare earth compound, is monoclinic phase at room temperature, and can be transformed into tetragonal phase at a certain temperature. In sintering of Ce2O3And Nb2O5Preferential formation of the mesophase CeNbO4Thereby remarkably reducing the sintering temperature and promoting the anisotropic growth of the alumina particles into a columnar shape. In addition, Ce2O3The compound is sintered with the surrounding alpha-Al2O3Grain bonding to form a grain phase CeAl11O18It also acts as a toughening effect by consuming more energy through columnar grain extraction. The pulling-out of the columnar crystal consumes more energy and can further strengthen the toughening effect. Thus, Ce is present in the additive2O3The content is higher than Nb2O5The content is 1.4-2.2. When the ratio is less than 1.4, the cerium oxide content is small, and thus the columnar crystal CeAl11O18The content is less or almost no, resulting in insignificant toughening effect. When the ratio is higher than 2.2, the intermediate phase CeNbO is removed4And CeAl11O18CeO tending to obviously yellow in the process of sintering ceramics2The thin layer is separated out, and the appearance and the electrical property of the ceramic are influenced.
In a preferred embodiment of the alumina ceramic sintered body of the present invention, the mass fraction of the niobium-containing compound (calculated as niobium oxide) is 2 to 6%, and the mass fraction of the cerium-containing compound (calculated as cerium oxide) is 2.8 to 8.4%.
In the invention, cerium oxide and niobium oxide are used as sintering aids to play roles in toughening and reducing sintering temperature. The rare earth elements are involved in the invention, so that the dosage is reduced as much as possible under the condition of meeting the performance, thereby reducing the cost. When Ce is present2O3Above 8.4%, a thin yellow layer of CeO may appear2Thereby affecting the appearance and electrical insulating properties of the ceramic substrate. When Nb2O5When the content is higher than 6%, the fracture toughness of the ceramic substrate is not improved any more, which proves that Nb is2O5The additive is saturated. Proved by experiments, the niobium-containing compound (calculated as niobium oxide)When the mass fraction of the cerium-containing compound is 2-6%, and the mass fraction of the cerium-containing compound (calculated in the form of cerium oxide) is 2.8-8.4%, the fracture toughness of the ceramic substrate is obviously improved, and when the mass fraction is less than the minimum value, the toughening effect cannot be achieved or is very little.
In a preferred embodiment of the alumina ceramic sintered body of the present invention, the raw material for producing the alumina ceramic sintered body does not contain zirconia.
Reasons for the absence of zirconia: (1) the cost of the zirconia is high, so that the cost of the ceramic substrate is greatly increased; (2) after the zirconia is added, the heat conduction coefficient of the ceramic substrate is greatly reduced, and the surface performance of the substrate is changed, so that the requirements of the ceramic substrate applied to metallization on heat dissipation and bonding force cannot be met.
As a preferred embodiment of the alumina ceramic sintered body of the present invention, the alumina ceramic sintered body is composed of, by mass fraction, 85.6 to 95.2% of alumina, 2 to 6% of a niobium-containing compound (calculated as niobium oxide), and 2.8 to 8.4% of a cerium-containing compound (calculated as cerium oxide).
Preferably, the alumina, Ce2O3、Nb2O5All are high purity powders of 99.99%.
As a preferred embodiment of the alumina ceramic sintered body of the present invention, the alumina ceramic sintered body is composed of, by mass fraction, 89% of alumina, 4% of a niobium-containing compound (calculated as niobium oxide), and 7% of a cerium-containing compound (calculated as cerium oxide). The finished product of the alumina substrate is composed of the components, and has the best fracture toughness and bending strength.
In a preferred embodiment of the alumina ceramic sintered body of the present invention, the alumina ceramic sintered body contains a cerium niobium crystal which is CeNbO4The alumina ceramic sintered body further contains a crystal grain phase CeAl formed by combining alumina and cerium oxide11O18. Wherein CeNbO4Is a main phase and has a relative content of CeNbO4：CeAl11O18The ratio is (1.3-1.6): 1.
as a preferred embodiment of the alumina ceramic sintered body of the present invention, the CeNbO4The average particle size of the particles is 3-4 um, and the difference value between D90 and D10 is 6.5-7.5 um; the CeAl11O18The average particle size of (2) is 3.5-4.5 um, and the difference between D90 and D10 is 7-8 um.
Mesophase CeNbO4Absorbing partial crack propagation energy mainly by switching domain structure, and partially heterodromous and growing Al2O3The crystal grains can make the crack generate deviation in the process of expanding, and consume part of fracture energy to achieve the aim of toughening, so the grain size distribution of the crystal grains has obvious influence on the performance of the ceramic substrate. When the average particle diameter is too large, CeNbO4The temperature of melting into liquid phase is higher, and the contact area with the surrounding alumina particles is relatively small, which is not beneficial to the dissolution and rearrangement of the alumina particles. When the average particle diameter is too small, CeNbO4The molten liquid phase is easy to migrate to the surface, resulting in poor surface roughness and other appearance properties of the ceramic substrate.
The purpose of the difference control of D90 and D10 is to ensure CeNbO4The centralization of the grain size ensures that the grain size is uniformly distributed and the toughening effect is strengthened. If the difference is too large, it may result in CeNbO4The domain structure of the crystal is arranged with overlarge difference, different CeNbO4A significant difference in domain width of the crystals occurred.
CeNbO at Normal temperature4The crystal is monoclinic phase, the point group is 2/m, and the crystal is changed into tetragonal phase at high temperature. CeNbO in alumina ceramic sintered body4The crystals exhibit an equidistant parallel domain structure. The CeNbO4When the crystal is subjected to external force and the external force is removed, certain strain force generated in the sintered body is converted into strain force through switching of the domain structure, and the strain force disappears. That is, the alumina ceramic sintered body of the present invention can pass CeNbO4The crystal domain structure has the switching characteristic to partially absorb crack propagation energy, so that Al is improved2O3Fracture toughness of the sintered body.
As a preferred embodiment of the alumina ceramic sintered body of the present invention, CeNbO per unit area is contained in the alumina ceramic sintered body4Of granular noodlesThe ratio of the CeAl to the CeAl is 3-6% in unit area11O18The particle area ratio of (A) is 2-3%.
The ratio of the particle area of the cerium niobium crystals per unit area means a value obtained by calculating the area of the cerium niobium crystals divided by the total area of the observed field of view from the cerium niobium crystals (not less than 1 μm) present in the field of view of a predetermined region on the mirror-polished surface of the alumina substrate.
The uniform distribution of the cerium niobium crystals is ensured (detection method: roughly calculating the area ratio through SEM images), and the mechanical properties of the ceramic substrate are greatly influenced. When the distribution density is too low, the cerium niobium crystals are mainly present between coarse alumina grain boundaries, and if the contact area between the cerium niobium crystals and the alumina grain boundaries is too small, the bonding force between alumina particles is small, resulting in a low strength of the ceramic substrate. When the distribution density is too high, the alumina bending strength is low because the thermal expansion coefficients of the alumina particles and the cerium-niobium crystal are different, such as the deformation of the grain boundary and the residual stress are easily caused if the contact area between the alumina particles and the cerium-niobium crystal is too large.
In a preferred embodiment of the alumina ceramic sintered body of the present invention, the alumina crystal has an aspect ratio of more than 3.
The aspect ratio of alumina affects the appearance of alumina grains, which in turn affects the toughness of the ceramic substrate. The columnar crystal of the alumina can reduce the crack tip propagation energy by deflecting the crack, extracting the columnar crystal to absorb energy and the like, so that the ceramic material has higher fracture toughness. The length-diameter ratio of the alumina crystal is controlled by the proportion of the raw materials and the additives, such as sintering temperature, heat preservation time or temperature control curve in the sintering process.
In a second aspect, the present invention provides an alumina ceramic substrate comprising the above alumina ceramic sintered body.
In a third aspect, the present invention provides a metal-layer-coated alumina ceramic substrate comprising the above alumina ceramic sintered body.
In a fourth aspect, the invention provides a copper-clad plate which comprises the aluminum oxide ceramic sintered body.
In a fifth aspect, the present invention provides a method for preparing the above alumina ceramic substrate, comprising the steps of:
(1) weighing raw materials, fully and uniformly mixing a cerium-containing compound (calculated in a cerium oxide form) and a niobium-containing compound (calculated in a niobium oxide form), then mixing the mixture with aluminum oxide, and then performing wet ball milling and drying to obtain mixed powder;
(2) and (2) putting the mixed powder obtained in the step (1) into a mould for isostatic pressing to obtain a green body, and sintering the green body at a high temperature to obtain the alumina ceramic substrate.
As a preferred embodiment of the preparation method of the alumina ceramic substrate, in the step (2), the temperature of the high-temperature sintering is 1450-1550 ℃, and the heat preservation time is 0.5-3 h.
And controlling the grain size distribution of the cerium-niobium crystal through specific high-temperature sintering temperature and heat preservation time. The length-diameter ratio of alumina grains in the alumina substrate is mainly limited by conditions such as raw material proportion, raw material characteristics, firing temperature, heat preservation time and the like. The ceramic substrate is mainly characterized in that the micro-morphology of the ceramic substrate is mainly equiaxial crystal grains when no additive is added, and the main crystal grains are obviously columnar after the additive is added and sintered at high temperature. The columnar crystal of the alumina can reduce the expansion energy of the crack tip by deflecting the crack, pulling out the columnar crystal to absorb energy and the like, so that the ceramic material has higher fracture toughness.
Preferably, after the raw materials are fully mixed, adding alcohol and corundum balls for wet grinding and mixing, drying the mixed powder suspension at 80-120 ℃, grinding by using a mortar, sieving by using a 100-mesh screen, and then pressing and forming by using a table type tablet press; and (3) placing the obtained green body at 1450-1550 ℃ for high-temperature sintering, keeping the temperature for 0.5-3 h, and naturally cooling to room temperature to obtain the high-toughness columnar alumina ceramic substrate.
Preferably, wet milling is adopted, and wet milling and mixing are carried out according to the volume ratio of (1-3) to (3-5) to (6-8) of the powder, the corundum balls and the solvent.
Preferably, the ball mill adopts a planetary ball mill, the diameter of the corundum ball is at least one of phi 8, phi 10 and phi 13, the ball-material ratio is controlled to be 2.5-4.0, the rotating speed of the ball mill is 300-800 r/min, and the ball milling time is 24-48 h.
Preferably, the solvent is at least one of ethanol, propanol, isopropanol, benzene, toluene, and ethylbenzene.
Preferably, after the ball milling is finished, the suspension is taken out and is dried in a constant-temperature drying oven at 90 ℃, and then the materials are crushed and screened by a 100-mesh screen for standby.
Preferably, a certain amount of the mixed powder is weighed and put into a metal die for isostatic pressing, and a green body with any geometric shape can be prepared according to requirements.
Preferably, the molded green body is placed into a muffle furnace or a microwave sintering furnace for high-temperature sintering, the molded green body is heated to 1450-1550 ℃ for sintering, the temperature is kept for 0.5-3 h, and after sintering, the power supply is turned off and the molded green body is cooled to room temperature along with the furnace.
Compared with the prior art, the invention has the beneficial effects that:
(1) the invention uses high-purity alpha-Al2O3Particles as raw material, using Ce2O3And Nb2O5As an additive, Ce is added in the sintering process2O3And Nb2O5Will generate CeNbO4As a liquid phase, the sintering temperature of the composite ceramic is obviously reduced, the interface reaction is promoted, and alumina crystal grains grow into a columnar shape in an anisotropic manner; the columnar crystal realizes the synergistic toughening of the composite ceramic mainly by deflecting the crack, pulling out the columnar crystal to absorb energy and the like, and reduces the expansion energy of the crack tip, so that the ceramic material has higher fracture toughness.
(2) The alumina ceramic substrate prepared by the invention has in-situ grown columnar alumina grains, the length-diameter ratio of the columnar grains is more than 3, and the fracture toughness of the ceramic substrate after sintering is 6.20-6.55 MPa.m1/2The bending strength is 433-486 MPa.
(3) The preparation method disclosed by the invention is simple in preparation process, simple and controllable in production, endows the ceramic substrate with excellent mechanical properties, is wide in application range, and especially can meet the requirements of the metal-layer-coated ceramic substrate on the ceramic surface and metal layer binding force, substrate heat dissipation, fracture toughness and bending strength.
Drawings
FIG. 1 is a Scanning Electron Microscope (SEM) image of the thermally etched columnar alumina grains in example 6 of the present invention.
FIG. 2 is a Weibull plot of the strength of the three-point bending test in example 6 of the present invention.
Detailed Description
To better illustrate the objects, aspects and advantages of the present invention, the present invention will be further described with reference to the accompanying drawings and specific embodiments.
(1) Effect of the amount of the sintered body component after molding of the invention
Examples 1-8 and comparative examples 1-4 were set to examine the effect of the mass fraction of the components in the finished product of the invention on the effect of the invention. The mass fractions of the components of the alumina ceramic sintered bodies in examples 1 to 8 and comparative examples 1 to 4 are shown in table 1.
TABLE 1
Niobium oxide (%) Cerium oxide (%) Alumina (%) Cerium oxide/niobium oxide
Example 1 2.0 2.8 95.2 1.40
Example 2 6.0 8.4 85.6 1.40
Example 3 3.5 5.0 91.5 1.43
Example 4 3.0 4.5 92.5 1.50
Example 5 2.5 4.2 93.3 1.68
Example 6 4.0 7.0 89 1.75
Example 7 4.3 8.2 87.5 1.91
Example 8 3.1 6.8 90.1 2.19
Comparative example 1 2.1 5.4 92.5 2.57
Comparative example 2 6.4 3.3 90.3 0.52
Comparative example 3 0 0 100.00 /
Comparative example 4 2.3 9.1 88.6 3.96
The preparation methods of examples 1 to 8 and comparative examples 1 to 4 were:
1) weighing the raw materials according to the proportion, fully and uniformly mixing cerium oxide and niobium oxide, and then mixing the mixture with high-purity Al2O3Mixing the powders, addingWet grinding and mixing alcohol and corundum balls, wherein the volume ratio of powder, corundum balls and solvent is 2:4:7, the ball grinding mill adopts a planetary ball grinding mill, the diameter of each corundum ball is at least one of phi 10, the ball-material ratio is controlled to be 3.2, the rotating speed of the ball grinding mill is 600r/min, the ball grinding time is 36 hours, the solvent is isopropanol and toluene, after the ball grinding is finished, the suspension is taken out and is placed in a constant-temperature drying box for drying at 90 ℃, then the materials are crushed, and the materials pass through a 100-mesh screen for standby;
2) and (3) putting the mixed powder into a table type tablet press, pressing and forming to obtain a green body, placing the green body at 1500 ℃ for high-temperature microwave sintering, keeping the temperature for 1h, and naturally cooling to room temperature along with a furnace after the heat preservation to obtain the aluminum oxide ceramic substrate.
The fracture toughness and the flexural strength of examples 1 to 8 and comparative examples 1 to 4 were measured, respectively, and the test results are shown in table 2. The method for testing the fracture toughness comprises the following steps: the fracture toughness of the composite material is measured by a three-point bending experiment through a unilateral notched beam method (SENB method) by adopting an electronic universal tester, and the loading rate is set to be 0.05 mm/min.
TABLE 2
Fracture toughness (MPa. m)1/2) Flexural Strength (MPa)
Example 1 6.21 452
Example 2 6.49 410
Example 3 6.24 476
Example 4 6.38 433
Example 5 6.46 447
Example 6 6.55 486
Example 7 6.29 462
Example 8 6.40 432
Comparative example 1 5.09 302
Comparative example 2 4.86 343
Comparative example 3 3.84 351
Comparative example 4 4.57 354
As can be seen from examples 1 to 8 and comparative example 3, the addition of cerium oxide and niobium oxide can significantly improve the fracture toughness of the ceramic substrate.
As can be seen from examples 1 to 8 and comparative examples 1 to 2, when the ratio of niobium oxide to cerium oxide is low, the fracture toughness of the ceramic substrate is obviously low; when the ratio of niobium oxide to cerium oxide is higher, the fracture toughness of the ceramic substrate is also lower.
In example 6, the best effect of the above example was obtained. Possibly due to the formation of CeAl if the cerium oxide content distribution is low11O18The content is less, resulting in a reduced toughening effect. That is, when the alumina ceramic sintered body is composed of 89% of alumina, 4% of a niobium-containing compound (calculated as niobium oxide) and 7% of a cerium-containing compound (calculated as cerium oxide), the alumina substrate has the best fracture toughness and bending strength.
Meanwhile, when the columnar alumina grains in example 6 were observed by Scanning Electron Microscope (SEM) after hot etching, as shown in fig. 1, it can be seen that the alumina grains mainly exhibit columnar appearance distribution and the aspect ratio is more than 3. Proved by experiments, equiaxed aluminum oxide grains really grow into columns in situ under the action of the additive, so that the toughening effect is achieved. The Weibull distribution of the strength of example 6 according to the three-point bending method is shown in FIG. 2, and it can be seen that the strength is 486.1MPa and the concentration of the strength data is good according to the three-point bending strength test.
Among them, the alumina ceramic sintered body formed in comparative example 4 was observed by naked eyes to have slight yellow spots on the surface of the sintered body, which seriously affected the bonding with the metal layer in the subsequent metallization process, and was not suitable for application to the metal-clad ceramic plate.
(2) Effect of average particle diameter of cerium niobium Crystal of the invention
The inventors tried a lot of experiments and found that CeNbO4And CeAl11O18The average particle diameter of (2) has a certain influence on the toughness and strength of the alumina ceramic substrate. Examples 9 to 13 and comparative examples 5 to 6 were selected to observe the influence of the average particle size of the cerium niobium crystal on the effect of the present invention. The average particle diameters of the cerium niobium crystals in examples 9 to 13 and comparative examples 5 to 6 are shown in Table 3.
TABLE 3
Figure BDA0002299605610000101
Figure BDA0002299605610000111
Meanwhile, the performance of the alumina ceramic substrates prepared in examples 9 to 13 and comparative examples 5 to 6 was tested, and the test results are shown in table 4.
TABLE 4
Fracture toughness (MPa. m)1/2) Flexural Strength (MPa)
Example 9 6.27 445
Example 10 6.38 468
Example 11 6.29 452
Example 12 6.50 476
Example 13 6.26 483
Comparative example 5 5.54 364
Comparative example 6 5.68 345
As can be seen from examples 9 to 13 and comparative examples 5 to 6, CeNbO4And CeAl11O18The average particle diameter of (A) has a certain influence on the toughness and strength of the alumina ceramic substrate when CeNbO4CeAl when the grain size of the crystal is distributed between 3.0 and 4.0um11O18When the grain size of the crystal is distributed in the range of 3.5-4.5 um, the fracture toughness and the bending strength of the alumina ceramic substrate are obviously enhanced. If the particle diameter falls outside the above range, the ceramic substrate is not significantly toughened.
(3) Effect of the Density distribution of the cerium niobium Crystal of the present invention
The inventors tried a lot of experiments and found that CeNbO4And CeAl11O18The distribution conditions of the cerium niobium crystals have certain influence on the toughness and the strength of the alumina ceramic substrate, and examples 14 to 18 and comparative examples 7 to 8 are selected to observe the density distribution of the cerium niobium crystals of the inventionInfluence of the effect of the invention. CeNbO in examples 14 to 18 and comparative examples 7 to 84And CeAl11O18The distribution of (A) is shown in Table 5. Wherein, CeNbO4And CeAl11O18The distribution of (A) is evaluated by observing SEM images and calculating the area ratio.
TABLE 5
Figure BDA0002299605610000112
Figure BDA0002299605610000121
Meanwhile, the performance of the alumina ceramic substrates prepared in examples 14 to 18 and comparative examples 7 to 8 was tested, and the test results are shown in table 6.
TABLE 6
Fracture toughness (MPa. m)1/2) Flexural Strength (MPa)
Example 14 6.25 437
Example 15 6.44 439
Example 16 6.39 481
Example 17 6.54 475
Example 18 6.18 458
Comparative example 7 5.91 396
Comparative example 8 5.64 408
As can be seen from examples 14 to 18 and comparative examples 7 to 8, CeNbO4And CeAl11O18The distribution of (A) has a certain influence on the toughness and strength of the alumina ceramic substrate when CeNbO4CeAl when the grain density distribution is 3-6%11O18When the density distribution is 2-3%, the toughening effect on the alumina ceramic substrate can be obvious. The bending strength and the fracture toughness of the ceramic substrate are temporarily and positively increased along with the increase of the density distribution; when the distribution density of the cerium niobium crystals is low, the toughening effect of the ceramic substrate is not obvious.
Finally, it should be noted that the above embodiments are only used for illustrating the technical solutions of the present invention and not for limiting the protection scope of the present invention, and although the present invention is described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that modifications or equivalent substitutions can be made on the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.

Claims (5)

1. An alumina ceramic sintered body is prepared from 85.6-95.2% by mass of alumina and 2-6% by mass of Nb2O5And 2.8-8.4% of Ce2O3Composition is carried out; the Ce2O3Mass fraction of (3) and Nb2O5The mass fraction ratio of (1.4-2.2): 1;
the alumina ceramic sintered body contains columnar alumina crystal grains growing in situ, and the length-diameter ratio of the columnar crystal grains of the alumina crystal grains is more than 3; the aluminum oxide ceramic sintered body contains cerium-niobium crystals, wherein the cerium-niobium crystals are CeNbO4The alumina ceramic sintered body further contains a crystal grain phase CeAl formed by combining alumina and cerium oxide11O18(ii) a The CeNbO4Has an average particle diameter of 3 to 4 μm and D90And D10The difference of (a) is 6.5-7.5 μm; the CeAl11O18Has an average particle diameter of 3.5 to 4.5 μm and D90And D10The difference value of (A) is 7-8 μm; in the alumina ceramic sintered body, CeNbO per unit area4The ratio of the grain area is 3-6%, CeAl in unit area11O18The particle area ratio of (A) is 2-3%.
2. The alumina ceramic sintered body as set forth in claim 1, wherein the raw materials of the alumina ceramic sintered body are composed of alumina in a mass fraction of 89%, Nb in a mass fraction of 4%2O5And 7 mass% of Ce2O3And (4) forming.
3. An alumina ceramic substrate, characterized in that the alumina ceramic substrate is composed of the alumina ceramic sintered body according to any one of claims 1 to 2.
4. A metal-clad alumina ceramic substrate, characterized in that the metal-clad alumina ceramic substrate is composed of the alumina ceramic sintered body according to any one of claims 1 to 2.
5. The method of preparing an alumina ceramic substrate according to claim 3, comprising the steps of:
(1) weighing raw materials according to the proportion, and mixing Ce2O3And Nb2O5Fully and uniformly mixing, then mixing with alumina, and then performing wet ball milling and drying to obtain mixed powder;
(2) putting the mixed powder obtained in the step (1) into a mould for isostatic pressing to obtain a green body, and sintering the green body at a high temperature to obtain the alumina ceramic substrate; wherein, in the high-temperature sintering process, the temperature is 1450-1550 ℃, and the heat preservation time is 0.5-3 h.
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