Zirconium oxide evaporation material and preparation method thereof

Abstract

The present application belongs to the technical field of optical thin film material production and discloses a method for preparing a zirconium oxide evaporation material. The method first comprises mixing zirconium oxide powder and pure water, homogenizing, and spray granulating to obtain powder one, then sintering powder one, sieving, and ball milling respectively after sieving to obtain powder two and powder three with different particle sizes; then mixing powder two and powder three in a mass ratio of 2-5:5-8 to obtain powder four, then mixing powder four with pure water, pressing into a green compact, and finally sintering the green compact a second time to obtain the zirconium oxide evaporation material. The present application uses powders of different particle sizes to mix and then press and sinter, which effectively increases the strength of the evaporation material and can reduce stress caused by temperature during the evaporation process, thereby reducing cracking. In addition, the present application also discloses a zirconium oxide evaporation material.

Description

Technical Field

[0001] The present application relates to the technical field of optical thin film material production, and in particular to a zirconium oxide evaporation material and a preparation method thereof. Background Art

[0002] Zirconia (ZrO2) has a high refractive index, low absorption rate in the visible light range, good thermal stability and mechanical properties, and the thin film layer made from it is strong, dense and stable. It is widely used in the preparation of lens coatings in various eyewear industries. However, zirconium oxide undergoes multiple phase transitions at different temperatures. These phase transitions can cause a large volume change effect. For example, when the heating temperature is greater than 1170°C, the zirconium oxide crystal form changes from monoclinic to tetragonal, and the volume shrinks by 7-9%. In addition, the thermal conductivity of zirconium oxide material is low and its resistance to thermal shock is poor, which causes the evaporation material to easily crack during the evaporation coating process, affecting product quality.

[0003] Chinese patent application 201810637368.7 discloses a stabilized zirconium oxide coating target and its preparation method, which uses zirconium oxide and yttrium oxide (stabilizer) powder as raw materials, and the weight ratio is: 100 parts of 300 mesh zirconium oxide, 90-110 parts of 1400 mesh zirconium oxide, and 30-50 parts of stabilizer, wherein the stabilizer is yttrium oxide or cerium oxide, or a composite stabilizer is used, and the above raw materials are mixed uniformly to obtain a mixed oxide; a binder is added to the mixed oxide, and the weight ratio is: 100 parts of mixed oxide, 0. .5 to 5 parts, add appropriate amount of water, mix evenly to obtain a bonding ingredient; dry the bonding ingredient obtained in the previous step in an oven to dry out the moisture, and the drying temperature is 90℃ to 110℃ to obtain a dry ingredient; place the dry ingredient obtained in the previous step in an alloy mold, press and form to obtain a sintering precursor; put the above sintering precursor into a container, place it in a vacuum sintering furnace for sintering, the vacuum degree is 0.01 Pa to 0.0001 Pa, the sintering temperature is 1600℃ to 2000℃, keep warm for 2 hours to 6 hours, and then naturally cool to room temperature to obtain a finished product.

[0004] A closer look at the specification sheet for this proposal reveals the following explanation of the role of phase change stabilizers in zirconia: "To achieve phase change toughening of zirconia, it is necessary to add a certain stabilizer and, under certain firing conditions, stabilize the high-temperature stable phase - tetragonal - to room temperature, thereby obtaining a tetragonal phase that can phase change at room temperature. This is the stabilizing effect of the stabilizer on zirconia." The specification also points out the mechanism of action of the zirconia stabilizer: "The cations of the stabilizer have a certain solubility in zirconia and can replace Zr therein to form a substitutional solid solution, hindering the transformation of the tetragonal phase to the monoclinic phase, thereby stably lowering the phase change point of zirconia to room temperature."

[0005] This solution can effectively solve the problem of cracking of zirconia coating targets, and can solve the problems of instability and refractive index non-uniformity in the coating process of traditional zirconia coating targets, improve the damage threshold of zirconia films, and ensure product quality. However, at the same time, the addition of stabilizers will also bring certain disadvantages. For example, when zirconia is used in the field of optical thin films, the addition of stabilizers will complicate the composition of the components, which will to a certain extent reduce the uniformity of optical properties such as transmittance and refractive index after coating, thereby reducing the performance of the film layer after zirconia coating.

[0006] Chinese patent application 202210267005.5 discloses a glass-bonded large-sized zirconia dense sintered product, which is composed of glass-coated zirconia spherical powder, zirconia small particles and monoclinic zirconia powder; the glass-coated zirconia spherical powder is a zirconia raw material with an inner core of electro-fused stabilized zirconia fine powder and an outer shell of glass phase; the glass-coated zirconia spheres account for 60-80% of the total mass of the entire product; the glass-bonded large-sized zirconia dense sintered product is a product formed by hydraulic or cold isostatic pressing. The chemical composition of large-sized dense sintered zirconia products is w(ZrO2+HfO2+CaO+Y2O3+MgO+SiO2+Al2O3+Na2O)≥99.0%, of which w(ZrO2+HfO2)≥85.0%, w(ZrO2+HfO2+CaO+Y2O3+MgO)≥90.0%, and w(SiO2+Al2O3+Na2O)=5%~10%. It can be seen that a variety of stabilizers are also used to prevent cracking of zirconia sintered products.

[0007] Chinese patent application 202180086939.2 discloses a zirconia calcined body, which comprises secondary aggregates with an average particle size of less than 275 nm, the secondary aggregates comprising zirconia and a stabilizer capable of inhibiting the phase change of zirconia, and the secondary aggregates comprising large particles with an average primary particle size of greater than 100 nm and less than 200 nm and small particles with an average primary particle size of greater than 10 nm and less than 60 nm. The zirconia powder obtained by the powder manufacturing method of this scheme and the zirconia formed body obtained by forming the composition containing zirconia can inhibit the occurrence of defects (blemishes), and therefore, the shape retention is excellent. At the same time, this scheme also adds a certain amount of stabilizer capable of inhibiting the phase change of zirconia during the preparation process.

[0008] It can be seen from the above literature that the volume change of zirconia caused by phase change during the sintering process is a widespread problem, and the use of stabilizers to inhibit phase change has become an important means commonly used to solve problems such as cracking caused by volume change during the sintering process of zirconia. However, in the field of optical thin film material manufacturing, although the use of additives can prevent the cracking of the optical film raw material, i.e., the evaporation source, during the sintering process, at the same time, once the stabilizer is added, the evaporation source will contain multiple components, and the multiple components will have different degrees of influence on the transmittance, refractive index, etc. of the film after being prepared into a thin film, resulting in differences in the optical properties of different parts of the film.

[0009] The problem to be solved by this solution is: how to provide a method for preparing zirconium oxide evaporation material, and prevent the evaporation material from cracking without using a stabilizer during the preparation process. Summary of the Invention

[0010] The purpose of the present application is to provide a method for preparing a zirconium oxide evaporative material. The method controls the particle size of the zirconium oxide powder used for sintering the zirconium oxide evaporative material and thus controls the voids between the zirconium oxide powders, thereby coping with the volume change of the zirconium oxide during the sintering process, utilizing the buffering effect of the voids, and reducing the occurrence of cracking problems caused by volume change during the phase transformation of the zirconium oxide.

[0011] To achieve the above objectives, the present application discloses a method for preparing a zirconium oxide evaporation material, comprising the following steps:

[0012] Step 1: Mixing zirconium oxide powder and pure water, homogenizing, and spray granulating to obtain powder 1;

[0013] Step 2: The powder obtained in step 1 is sintered and sieved, and then ball-milled for 3-8 hours and 15-30 hours respectively to obtain powder 2 with a particle size of 15-35 μm and powder 3 with a particle size of 2-8 μm;

[0014] Step 3: Powder 2 and powder 3 are mixed in a mass ratio of 2-5:5-8 to obtain powder 4, powder 4 is mixed with pure water, pressed into a green body, and then the green body is secondary sintered to obtain zirconium oxide evaporation material;

[0015] The temperature of the first sintering is 1300-1600° C., and the sintering time is 3-10 hours; the temperature of the second sintering is 950-1150° C., and the sintering time is 3-10 hours.

[0016] Preferably, step 1 is specifically as follows: zirconium oxide powder and pure water are weighed in a ratio of 20 to 50:1, and then the pure water is added to the zirconium oxide powder in a rotary mixer by atomizing spray, mixed and homogenized, spray granulated, and sieved to obtain powder 1.

[0017] Preferably, step 2 is specifically as follows: the powder 1 obtained in step 1 is charged into a sintering furnace, and sintered once under normal air pressure conditions, and during the first sintering process, the temperature is first increased to 1300-1600°C at a heating rate of 10-30°C / min, and then kept warm for 3-10 hours. After the insulation is completed, the powder is cooled to room temperature at a cooling rate of 10-30°C / min. After cooling, the powder is sieved and the sieved powder is ball-milled for 3-8 hours and 15-30 hours respectively to obtain a powder 2 with a particle size of 15-35um and a powder 3 with a particle size of 2-8um.

[0018] Preferably, the green compact pressing process in step 3 is as follows: powder 2 and powder 3 obtained in step 2 are mixed in a mass ratio of 2 to 5: 5 to 8 to obtain powder 4, powder 4 is mixed with pure water in a mass ratio of 25 to 50: 1, and then the mixture of powder 4 and water is placed in a uniaxial tablet press and pressed into a green compact. During the pressing process, the pressure is 15 to 50 MPa and the pressing time is 5 to 20 s.

[0019] Preferably, the secondary sintering process in step 3 is specifically as follows: the pressed green body is placed in a sintering furnace for secondary sintering. During the secondary sintering process, the temperature is first increased to 950°C to 1150°C at a heating rate of 10 to 30°C / min, and then kept warm for 3 to 10 hours. After the insulation is completed, the temperature is cooled to room temperature at a cooling rate of 10 to 30°C / min to obtain a zirconium oxide evaporation material.

[0020] Preferably, when the particle size of powder 2 is 28-32 μm and the particle size of powder 3 is 5-8 μm, in step 3, the mass ratio of powder 2 to powder 3 is 3-4:6-7.

[0021] In addition, the present application also discloses a zirconium oxide evaporation material, which is characterized in that it is prepared by the above-mentioned preparation method of the zirconium oxide evaporation material, and the relative density of the prepared zirconium oxide evaporation material is 65-85%.

[0022] The beneficial effect of the present application is that the preparation method of the zirconia evaporative material provided in the present application controls the particle size of the zirconia powder used for sintering the zirconia evaporative material, thereby controlling the voids between the zirconia powders, thereby coping with the volume change of the zirconia during the sintering process, and utilizing the buffering effect of the voids to reduce the occurrence of cracking problems caused by volume changes during the phase transformation of the zirconia. DETAILED DESCRIPTION

[0023] The present invention will be described clearly and completely below in conjunction with the examples of the present invention. In the description of the present invention, it should be noted that if specific conditions are not specified in the examples, the experiments were carried out according to conventional conditions or the conditions recommended by the manufacturer. The reagents or instruments used, if the manufacturer is not specified, are all conventional products that can be purchased commercially.

[0024] Example 1

[0025] Step 1: Weigh zirconium oxide powder with a purity of 99.9% and D90 = 0.2 μm and pure water in a mass ratio of 50:1, add the pure water to the zirconium oxide powder in a rotary mixer by atomizing spray, mix and homogenize, spray granulate, and sieve to obtain powder 1;

[0026] Step 2: The powder prepared in step 1 is charged into a sintering furnace and sintered once under normal air pressure. First, the temperature is increased to 1600°C at a heating rate of 20°C / min and kept at this temperature for 10 hours. After keeping at this temperature, the powder is cooled to room temperature at a cooling rate of 20°C / min to obtain an intermediate powder, which is sieved and divided into two parts. The powders are charged into polyurethane ball mills and ball milled for 8 hours and 20 hours, respectively, to obtain a powder 2 with a particle size of 15 μm and a powder 3 with a particle size of 5 μm.

[0027] Step 3: Powder 2 and powder 3 obtained in step 2 are mixed in a mass ratio of 2:8 to obtain powder 4, powder 4 is mixed with pure water in a mass ratio of 25:1, and then the mixture of powder 4 and water is placed in a uniaxial tablet press to form a green body. During the pressing process, the pressure is 15 MPa and the pressing time is 10 s. The green body is then placed in a sintering furnace, first heated to 1000°C at a heating rate of 5°C / min, and kept warm for 5 hours. After the insulation is completed, it is cooled to room temperature at a cooling rate of 5°C / min; the measured relative density of the evaporating material is 70%, and there is no cracking. Through SEM detection, the average size of the coarse particles is 35um and the average size of the fine particles is 8um.

[0028] Example 2

[0029] Step 1: Weigh zirconium oxide powder with a purity of 99.9% and D90 = 0.4 μm and pure water in a mass ratio of 30:1, add the pure water to the zirconium oxide powder in a rotary mixer by atomizing spray, mix and homogenize, spray granulate, and sieve to obtain powder 1;

[0030] Step 2: The powder prepared in step 1 is charged into a sintering furnace and sintered once under normal air pressure. The temperature is first increased to 1500°C at a heating rate of 10°C / min and held for 8 hours. After holding, the powder is cooled to room temperature at a cooling rate of 10°C / min to obtain an intermediate powder, which is sieved and divided into two parts. The powder is charged into a polyurethane ball mill and ball milled for 6 hours and 30 hours, respectively, to obtain a powder 2 with a particle size of 20 μm and a powder 3 with a particle size of 2 μm.

[0031] Step 3: Powder 2 and powder 3 obtained in step 2 are mixed in a mass ratio of 5:5 to obtain powder 4, powder 4 is mixed with pure water in a mass ratio of 40:1, and then the mixture of powder 4 and water is placed in a uniaxial tablet press to be pressed into a green body. During the pressing process, the pressure is 30 MPa and the pressing time is 15 s. The green body is then placed in a sintering furnace, first heated to 1150°C at a heating rate of 10°C / min, and kept warm for 10 hours. After the insulation is completed, it is cooled to room temperature at a cooling rate of 10°C / min; the measured relative density of the evaporating material is 75%, and there is no cracking. Through SEM detection, the average size of the coarse particles is 35um and the average size of the fine particles is 3um.

[0032] Example 3

[0033] Step 1: Weigh zirconium oxide powder with a purity of 99.9% and D90 = 1 μm and pure water in a mass ratio of 20:1, add the pure water to the zirconium oxide powder in a rotary mixer by atomizing spray, mix and homogenize, spray granulate, and sieve to obtain powder 1;

[0034] Step 2: Powder 1 prepared in step 1 is charged into a sintering furnace and sintered once under normal air pressure. First, the temperature is increased to 1400°C at a heating rate of 30°C / min and kept at this temperature for 3 hours. After keeping at this temperature, the temperature is cooled to room temperature at a cooling rate of 30°C / min to obtain an intermediate powder, which is sieved and divided into two parts. The two parts are charged into a polyurethane ball mill and ball milled for 3 hours and 15 hours respectively to obtain powder 2 with a particle size of 35 μm and powder 3 with a particle size of 8 μm.

[0035] Step 3: Powder 2 and powder 3 obtained in step 2 are mixed in a mass ratio of 4:6 to obtain powder 4, powder 4 is mixed with pure water in a mass ratio of 50:1, and then the mixture of powder 4 and water is placed in a uniaxial tablet press to be pressed into a green body. During the pressing process, the pressure is 40 MPa and the pressing time is 5 s. The green body is then placed in a sintering furnace, first heated to 1100°C at a heating rate of 10°C / min, and kept warm for 3 hours. After the insulation is completed, it is cooled to room temperature at a cooling rate of 10°C / min; the measured relative density of the evaporating material is 80%, and there is no cracking. Through SEM detection, the average size of the coarse particles is 40um and the average size of the fine particles is 10um.

[0036] Example 4

[0037] Step 1: Weigh zirconium oxide powder with a purity of 99.95% and D90 = 1 μm and pure water in a mass ratio of 40:1, add the pure water to the zirconium oxide powder in a rotary mixer by atomizing spray, mix and homogenize, spray granulate, and sieve to obtain powder 1;

[0038] Step 2: The powder from step 1 was charged into a sintering furnace and sintered once under normal air pressure. The temperature was first increased to 1300°C at a heating rate of 10°C / min and held for 5 hours. After holding, the mixture was cooled to room temperature at a cooling rate of 10°C / min to obtain an intermediate powder. The intermediate powder was sieved and divided into two parts. The powders were charged into polyurethane ball mills and ball milled for 4 hours and 25 hours, respectively, to obtain a second powder with a particle size of 30 μm and a third powder with a particle size of 3 μm.

[0039] Step 3: Powder 2 and powder 3 obtained in step 2 are mixed in a mass ratio of 3:7 to obtain powder 4, powder 4 is mixed with pure water in a mass ratio of 35:1, and then the mixture of powder 4 and water is placed in a uniaxial tablet press to be pressed into a green body. During the pressing process, the pressure is 50 MPa and the pressing time is 8 s. The green body is then placed in a sintering furnace, first heated to 950°C at a heating rate of 5°C / min, and kept warm for 5 hours. After the insulation is completed, it is cooled to room temperature at a cooling rate of 5°C / min; the measured relative density of the evaporating material is 85%, and there is no cracking. Through SEM detection, the average size of the coarse particles is 35um and the average size of the fine particles is 6um.

[0040] Example 5

[0041] The method is basically the same as Example 1, except that in step 2, the intermediate powder is sieved and divided into two parts, which are loaded into a polyurethane ball mill and ball milled for 3.5 hours and 15 hours, respectively, to obtain powder 2 with a particle size of 32 μm and powder 3 with a particle size of 8 μm. In step 3, the mass ratio of powder 2 to powder 3 is 3:7. The relative density of the obtained evaporation material is measured to be 73%, and there is no cracking. SEM detection shows that the average size of coarse particles is 37 μm, and the average size of fine particles is 10 μm.

[0042] Example 6

[0043] The method is basically the same as Example 1, except that in step 2, the intermediate powder is sieved and divided into two parts, which are loaded into a polyurethane ball mill and ball milled for 4.5 hours and 20 hours, respectively, to obtain powder 2 with a particle size of 28 μm and powder 3 with a particle size of 5 μm. In step 3, the mass ratio of powder 2 to powder 3 is 4:6. The relative density of the obtained evaporation material is measured to be 80%, and there is no cracking. SEM detection shows that the average size of coarse particles is 33 μm, and the average size of fine particles is 9 μm.

[0044] Comparative Example 1

[0045] The method is basically the same as Example 1, except that in step 3, powder 2 with a particle size of 10 μm and powder 3 with a particle size of 10 μm are used to prepare powder 4. The relative density of the obtained evaporation material is measured to be 63%, and there is obvious cracking. SEM detection shows that the average size of coarse particles is 12 μm, and the average size of fine particles is 10 μm.

[0046] Comparative Example 2

[0047] The method is basically the same as Example 1, except that in step 3, the mass ratio of powder 2 to powder 3 is 1:9. The relative density of the evaporation material obtained is measured to be 67%, and there is obvious cracking. SEM detection shows that the average size of coarse particles is 35 μm, and the average size of fine particles is 8 μm.

[0048] Comparative Example 3

[0049] The method is basically the same as Example 1, except that in step 3, the mass ratio of powder 2 to powder 3 is 6:4. The relative density of the obtained evaporation material is measured to be 73%, and there is slight cracking. SEM detection shows that the average size of coarse particles is 35 μm, and the average size of fine particles is 8 μm.

[0050] Comparative Example 4

[0051] It is basically the same as Example 1, except that, in step 3, the secondary sintering process is specifically as follows: placing the green body in a sintering furnace, first heating it to 700°C at a heating rate of 5°C / min, keeping it warm for 5 hours, and then cooling it to room temperature at a cooling rate of 5°C / min after the insulation is completed. The relative density of the obtained evaporation material is measured to be 69%, with obvious cracking; through SEM detection, the average size of the coarse particles is 34um, and the average size of the fine particles is 7um.

[0052] Result Analysis

[0053] 1. As can be seen from Examples 1-4, after slightly changing the parameters during the preparation of the zirconium oxide evaporation material, none of the evaporation materials prepared in Examples 1-4 experienced cracking. This shows that slightly adjusting the parameters during the preparation of the zirconium oxide evaporation material has little effect on the zirconium oxide evaporation material. Furthermore, after further adjusting the particle sizes of Powder 2 and Powder 3 in Examples 5 and 6, no cracking occurred in Examples 5 and 6. Furthermore, in actual use, the optical properties of the films, such as light transmittance during the coating process, of Examples 5 and 6 were superior to those of Examples 1-4. Therefore, we highly recommend the parameters provided in Examples 5 and 6.

[0054] 2. It can be seen from Example 1 and Comparative Example 1 that when Powder 2 and Powder 3, both with a particle size of 10 μm, are used to prepare the zirconia evaporation material, the evaporation material exhibits obvious cracking. This shows that using powders of the same particle size to prepare the zirconia evaporation material cannot suppress or offset the stress caused by the phase change of zirconia during the sintering process. At the same time, observation of Comparative Examples 2 and 3 also shows that when the mass ratio between Powder 2 and Powder 3 is significantly adjusted, the zirconia evaporation material also exhibits obvious cracking. This shows that the mass ratio between the large-particle-size Powder 2 and the small-particle-size Powder 3 is equally important in this method.

[0055] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principles of the present invention should be considered as equivalent replacement methods and are included in the scope of protection of the present invention.

Claims

1. A method for preparing a zirconium oxide evaporation material, characterized in that: The following steps are involved: Step 1: Mixing zirconium oxide powder and pure water, homogenizing, and spray granulating to obtain powder 1; Step 2: The powder obtained in step 1 is sintered and sieved, and then ball-milled for 3-8 hours and 15-30 hours respectively to obtain powder 2 with a particle size of 15-35 μm and powder 3 with a particle size of 2-8 μm; Step 3: Powder 2 and powder 3 are mixed in a mass ratio of 2-5:5-8 to obtain powder 4, powder 4 is mixed with pure water, pressed into a green body, and then the green body is secondary sintered to obtain zirconium oxide evaporation material; The temperature of the first sintering is 1300-1600° C., and the sintering time is 3-10 hours; the temperature of the second sintering is 950-1150° C., and the sintering time is 3-10 hours.

2. The method for preparing the zirconium oxide evaporation material according to claim 1, wherein: The step 1 specifically comprises: weighing zirconium oxide powder and pure water in a ratio of 20 to 50:1, then adding the pure water into the zirconium oxide powder in a rotary mixer by atomizing spray, mixing and homogenizing, spray granulating, and sieving to obtain powder 1.

3. The method for preparing the zirconium oxide evaporation material according to claim 1, wherein: The step 2 specifically comprises: charging the powder 1 obtained in the step 1 into a sintering furnace, and performing a primary sintering under normal air pressure conditions. During the primary sintering process, the powder is first heated to 1300-1600° C. at a heating rate of 10-30° C. / min, then kept warm for 3-10 hours, and after the insulation is completed, cooled to room temperature at a cooling rate of 10-30° C. / min. After cooling, the powder is sieved and the sieved powder is ball-milled for 3-8 hours and 15-30 hours, respectively, to obtain a powder 2 with a particle size of 15-35 μm and a powder 3 with a particle size of 2-8 μm.

4. The method for preparing the zirconium oxide evaporation material according to claim 1, wherein: The green compact pressing process in step 3 is as follows: powder 2 and powder 3 obtained in step 2 are mixed in a mass ratio of 2-5:5-8 to obtain powder 4, powder 4 is mixed with pure water in a mass ratio of 25-50:1, and then the mixture of powder 4 and water is placed in a uniaxial tablet press and pressed into a green compact. During the pressing process, the pressure is 15-50 MPa and the pressing time is 5-20 s.

5. The method for preparing the zirconium oxide evaporation material according to claim 1, wherein: The secondary sintering process in step 3 is specifically as follows: the pressed green body is placed in a sintering furnace for secondary sintering. During the secondary sintering process, the temperature is first increased to 950°C to 1150°C at a heating rate of 10 to 30°C / min, and then kept warm for 3 to 10 hours. After the insulation is completed, the temperature is cooled to room temperature at a cooling rate of 10 to 30°C / min to obtain zirconium oxide evaporation material.

6. The method for preparing the zirconium oxide evaporation material according to claim 1, wherein: When the particle size of powder 2 is 28-32 μm and the particle size of powder 3 is 5-8 μm, in step 3, the mass ratio of powder 2 to powder 3 is 3-4:6-7.

7. A zirconium oxide evaporation material, characterized in that: The zirconium oxide evaporation material is prepared by the preparation method of any one of claims 1 to 6, and the prepared zirconium oxide evaporation material has a relative density of 65 to 85%.