A rare earth target material and preparation method thereof

Abstract

The invention relates to a rare earth target material and a preparation method thereof, and provides a rare earth cerium target material with long-life stability in the air. The target material adopts a high-purity metal cerium raw material, and is smelted into a metal melt by a water-cooled crucible suspension smelting method; then, an ingot is pulled down to obtain a metal cerium ingot, and the obtained metal cerium ingot is rolled, cut and processed, and heat-treated; after the heat treatment and cooling, the cerium target material is subjected to hydrogen plasma treatment, and a high-quality cerium target material with a cerium content of ≥99.99wt%, a density of >98%, and an oxygen content of <500ppm is obtained by performing a specific hydrogen plasma treatment on the surface of the target material, thereby effectively improving the oxidation resistance of the cerium target material, and without introducing other impurity components, the target material can be directly used for sputtering and coating without pretreatment, is easy to use, can be industrially produced on a large scale, has low cost, has good oxidation resistance and storage stability, and can realize large-scale industrial production.

Description

Technical Field

[0001] The invention relates to a rare earth target material and a preparation method thereof, belonging to the technical field of metal target materials, and in particular to a rare earth cerium target material. Background Art

[0002] PVD technology is the core technology of many industries such as semiconductor chip manufacturing, solar energy industry, LCD manufacturing industry, etc. The main methods include vacuum evaporation, arc plasma plating, ion plating, molecular beam epitaxy and sputtering coating. Sputtering is one of the main ways to prepare thin film materials or introduce a certain component of the product. The substrate used is called a target material. According to the type of material, the target material includes metal and alloy targets, inorganic non-metallic targets and composite targets. At the same time, rare earth is an important strategic resource in my country and plays a vital role in the country's strategic emerging industries. Due to its special optical, electrical, magnetic and superconducting properties, rare earth is widely used in new materials, steel and non-ferrous metal products, especially in the development of aerospace industry, military equipment, household appliances, new energy, nuclear industry and other fields. It plays an indispensable role. Preparing rare earth elements into targets and sputtering them for material composite, modification or functional layer preparation is a more common way to utilize rare earth materials.

[0003] Metal cerium is an important rare earth element and the most abundant rare earth element. It has unique physical and chemical properties and is often used as a reducing agent, catalyst, and alloy additive. It has important and extensive uses in modern industry. The use of cerium target material magnetron sputtering to prepare metal cerium is also a commonly used method for preparing metal cerium thin films or alloy materials. However, the chemical properties of metal cerium are very active. It is easy to oxidize in the air and corrode in a humid environment. At the same time, cerium can react with most metals and non-metals at high temperatures, making it easy for oxygen impurities to be introduced into the cerium target material during placement and oxidized, resulting in changes in the coating and reduced purity. This seriously limits the promotion and application of metal cerium targets. At present, the oxidation resistance of the target material is usually improved by preparing a coating on the surface of metal cerium. For example, CN106835015A discloses a method for modifying the surface of metal cerium. Using a dual ion beam sputtering deposition system, the polished metal cerium surface is firstly subjected to argon ion sputtering cleaning, then subjected to nitridation reaction sputtering treatment to generate a cerium nitride coating, and finally subjected to sputtering to generate a titanium nitride ceramic coating, and finally a double-layer coating of cerium nitride and titanium nitride composite is formed on the cerium surface, so that the anti-aging corrosion performance of metal cerium is significantly enhanced. However, the surface protection coating will inevitably introduce impurities, which is very unfavorable for the use of the target material. In addition, some people place the cerium target in kerosene to isolate it from air for storage, but it is also impossible to avoid the appearance of impurities in the sputtering coating caused by surface oxidation during use. Although the surface sputtering treatment before using the cerium target coating can improve the purity of the product, it also virtually increases the process and leads to the waste of raw material target material. Based on this, it is necessary to provide a clean metal cerium target material without an oxide film layer and capable of maintaining a certain degree of anti-oxidation stability in the air, so as to reduce oxidation of the cerium target material during storage, improve the storage stability of the target material and obtain a cerium coating with higher purity. Summary of the invention

[0004] The purpose of the present invention is to overcome the above-mentioned deficiencies in the prior art and to provide a metal cerium target material and a target material preparation method. By subjecting the formed target material to hydrogen plasma treatment, the oxidation resistance of the cerium target material is effectively improved without introducing other impurity components. The target material can be directly used for sputtering coating without pretreatment. It is easy to use and can be mass-produced industrially at a low cost, further expanding its application range.

[0005] In order to solve the defects in the prior art, the present invention provides a method for preparing a rare earth target material, wherein the rare earth is cerium, and the method comprises the following steps:

[0006] (1) Weigh a certain mass of high-purity metallic cerium; the cerium content in the metallic cerium is ≥ 99.99wt%, and the metallic cerium raw material can be a cerium plate, a cerium wire, a cerium foil, a metallic cerium particle, a cerium block or a cerium rod.

[0007] (2) The weighed metallic cerium is smelted into a cerium melt by a water-cooled crucible suspension smelting method.

[0008] (3) The cerium melt is pulled down to form an ingot to obtain a metal cerium ingot, and the obtained metal cerium ingot is rolled and sheared; the sheared cerium target is round with a diameter of 5 to 100 mm.

[0009] (4) Heat treatment is performed on the cut cerium ingot. Heat treatment can improve the density of the target material and avoid the sudden release of gas in the internal pores of the target material during sputtering coating due to the low density, large internal pores and gas presence of the target material obtained by the melt casting method itself, which causes large-sized target particles or microparticles to splash, thereby affecting the quality of the target material or reducing the quality of the sputtered film.

[0010] (5) The cerium target material after heat treatment and cooling is subjected to hydrogen plasma treatment.

[0011] Furthermore, before smelting in step (2), raw materials of the same composition are repeatedly smelted in a water-cooled crucible to clean the crucible; argon gas is passed during the smelting process to avoid oxidation, and the pressure in the suspension smelting furnace is 300 to 500 Pa higher than the atmospheric pressure.

[0012] Furthermore, the step (3) of pulling down the ingot is as follows: a water-cooled crucible containing cerium melt is pulled down at a speed of 0.1-1 mm / min, and during the pulling down process, the cerium melt is gradually cooled and solidified, while ultrasonic treatment is performed on the cerium melt to refine the grains, thereby obtaining a cerium ingot; wherein the frequency of the ultrasonic wave is 20 kHz-40 kHz, and the power of the ultrasonic instrument is 20 kW-40 kW.

[0013] Furthermore, the rolling and cutting process in step (3) is specifically as follows: after the metal cerium ingot cools to room temperature, it is placed in a vacuum heat treatment furnace and evacuated to 1×10 -1 Pa~1×10 -4 After Pa, the temperature is raised to 330℃~400℃ and kept for 2~3h, and then cooled with the furnace; a two-roll rolling mill is used to cold-roll the product to the required thickness to obtain a cold-rolled product; the cold-rolled product is cut into the required target size.

[0014] Furthermore, the heat treatment in step (4) is carried out in a manner of sequentially quenching and tempering in an argon atmosphere, specifically, placing the cut cerium ingot in a vacuum heat treatment furnace and evacuating the vacuum to 1×10 -1 Pa~1×10 -4 Pa, and then heated to 400℃~500℃, and then immediately placed in cooling oil for cooling, and then placed in a vacuum heat treatment furnace, and evacuated to 1×10 -1 Pa~1×10 2Pa and then heat to 100℃~150℃ and keep it for 1~3h. Tempering can also adopt gradient heat preservation, such as 100℃ for 1~2h and 150℃ for 1~2h. The segmented gradient heat preservation method can promote the connection and shrinkage of the pores inside the target material and improve the density of the target material. There is no special requirement for the heating rate, which can be 20~50℃ / min as a preferred method.

[0015] Furthermore, the hydrogen plasma treatment in step (5) is specifically as follows: placing the cerium target material after heat treatment and cooling in a vacuum heat treatment furnace, and evacuating the vacuum to 1×10 -1 Pa~1×10 2 After 300-500°C, argon and hydrogen are introduced at a flow rate ratio of 2-10:1; heated to 300-500°C, the gas flow rate is adjusted to keep the gas pressure in the vacuum heat treatment furnace at 500-1000Pa, and the RF power is turned on with a power of 200W to ionize the gas in the vacuum heat treatment furnace to generate plasma, and the gas is cooled and taken out after treatment for 0.5-1h. The hydrogen gas flow rate can be 100-500sccm.

[0016] Furthermore, the preparation method of the rare earth target comprises the following steps: placing a block of cerium with a purity of 99.99wt% into a water-cooled crucible of a suspension smelting furnace, repeatedly smelting for 3 times under an argon atmosphere and then pouring it out, adding a block of cerium with a purity of 99.99wt% into the water-cooled crucible, smelting under an argon atmosphere, and controlling the pressure in the suspension smelting furnace to be higher than the atmospheric pressure by 400Pa until the block of cerium is smelted into a cerium melt; pulling down the water-cooled crucible containing the cerium melt at a speed of 0.1-1mm / min, and while the cerium melt is gradually cooled and solidified during the pulling down process, ultrasonic treatment is performed on the cerium melt to refine the grains to obtain a cerium ingot; wherein the frequency of the ultrasonic wave is 30kHz, and the power of the ultrasonic instrument is 30kW; after the cerium ingot cools to room temperature, it is placed in a vacuum heat treatment furnace and evacuated to 1×10 -4 Pa, the temperature was raised to 400℃ and kept for 2h, and then cooled with the furnace; a two-roll mill was used to cold-roll the product to 5mm to obtain a cold-rolled product; the cold-rolled product was cut into discs with a diameter of 5cm; the disc cerium target was placed in a vacuum heat treatment furnace and evacuated to 1×10 -4 Pa and then heated to 500 °C and immediately placed in cooling oil for cooling. Then placed in a vacuum heat treatment furnace and evacuated to 1 × 10 2 Pa, then heat to 150℃ and keep warm for 1h; continue to evacuate to 1×10 -1 Pa, argon and hydrogen are introduced at a flow ratio of 10:1; heated to 450°C, the gas flow rate is adjusted to make the gas pressure in the vacuum heat treatment furnace 1000Pa, and the radio frequency power supply is turned on with a power of 200W to ionize the gas in the vacuum heat treatment furnace to generate plasma. After treating for 1 hour, it is cooled and taken out.

[0017] Another object of the present invention is to provide a rare earth cerium target material, wherein the surface of the target material is subjected to hydrogen plasma treatment after being formed. The hydrogen plasma treatment is to generate active hydrogen plasma by ionization using a radio frequency power supply under a certain vacuum degree, and the active hydrogen plasma is applied to the surface of the cerium target material and the area near the surface. On the one hand, the active components in the plasma can undergo a reduction reaction with the oxide on the surface of the metal cerium to generate water vapor, which can effectively remove the impurity oxygen on the surface of the target material; on the other hand, some active ions will be adsorbed on the surface of the cerium target material and form a reduced layer in the area near the outer surface, further protecting the metal from oxidation and improving the storage stability of the target material. The hydrogen plasma treatment is specifically as follows: the formed cerium target material is placed in a vacuum heat treatment furnace and evacuated to 1×10 -1 Pa~1×10 2 Pa, introduce argon and hydrogen at a flow ratio of 2 to 10:1; heat to 300 to 500°C, adjust the gas flow rate to keep the gas pressure in the vacuum heat treatment furnace at 500 to 1000Pa, turn on the RF power supply with a power of 200W to ionize the gas in the vacuum heat treatment furnace to generate plasma, and cool after treating for 0.5 to 1h.

[0018] Furthermore, the rare earth target material has a thickness of 1-10 mm.

[0019] Furthermore, the cerium content in the target material is ≥99.99wt%, the density of the target material is >98%, the oxygen content in the target material is <500ppm, and the average grain size of the rare earth target material is ≤100μm.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] 1. The cerium content in the rare earth cerium target prepared by the present invention is ≥99.99wt%, the density of the target is >98%, the oxygen content in the target is <500ppm, the average grain size of the rare earth target is ≤100μm, and it has high purity and a size distribution in a large range. The special treatment of the cerium target by the present invention helps to reduce the content of impurities such as oxygen inside the target and improve the overall purity of the target; at the same time, a reduced layer can also be formed on the surface area of ​​the cerium target, which can serve as a barrier layer for external oxygen to diffuse into the target, preventing the metal cerium from oxidizing when exposed to an oxidizing environment for a long time. The target itself has long-term oxidation resistance.

[0022] 2. The preparation process of the present invention is simple, without introducing other impurities, the target material has high density, fewer internal pores, and high purity. It can be directly used for sputtering coating without pretreatment. It is easy to use and can be mass-produced industrially, with low cost, good sputtering film formation, and good market prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is the SEM image of the cerium target prepared in Example 1. DETAILED DESCRIPTION

[0024] In order to make the technical problems solved by the present invention, the technical solutions adopted and the technical effects achieved clearer, the technical solutions of the embodiments of the present invention are further described in detail below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0025] It should be noted that the reference to "embodiment" in this document means that the specific features, structures or characteristics described in conjunction with the embodiment may be included in at least one embodiment of the present application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0026] The experimental methods in the following examples are conventional methods unless otherwise specified. The materials, reagents, etc. used in the following examples are commercially available unless otherwise specified.

[0027] Example 1

[0028] A method for preparing a cerium target material comprises the following steps: placing a block of cerium with a purity of 99.99wt% into a water-cooled crucible of a suspension smelting furnace, repeatedly smelting 4 times in an argon atmosphere and then pouring it out, adding a block of cerium with a purity of 99.99wt% into the water-cooled crucible, smelting in an argon atmosphere, controlling the pressure in the suspension smelting furnace to be higher than the atmospheric pressure by 300Pa until the block of cerium is smelted into a cerium melt; pulling down the water-cooled crucible containing the cerium melt at a speed of 0.1mm / min, and while the cerium melt is gradually cooled and solidified during the pulling down process, ultrasonic treatment is performed on the cerium melt to refine the grains to obtain a cerium ingot; wherein the frequency of the ultrasonic wave is 20kHz, and the power of the ultrasonic instrument is 20kW; after the cerium ingot is cooled to room temperature, it is placed in a vacuum heat treatment furnace, and vacuumized to 1×10 -1 Pa, the temperature was raised to 330℃ and kept for 2h, and then cooled with the furnace; a two-roll mill was used to cold-roll the product to a thickness of 1mm to obtain a cold-rolled product; the cold-rolled product was cut into discs with a diameter of 10mm; the disc cerium target was placed in a vacuum heat treatment furnace and evacuated to 1×10 -1 Pa and then heated to 400 °C and immediately placed in cooling oil for cooling. Then placed in a vacuum heat treatment furnace and evacuated to 1 × 10 -1 Pa and then heated to 100℃ and kept warm for 1h; the vacuum degree was maintained at 1×10 -1Pa, argon and hydrogen are introduced at a flow ratio of 2:1, and the hydrogen gas flow rate is 100 sccm; heat to 300°C, adjust the gas flow rate to keep the gas pressure in the vacuum heat treatment furnace at 500Pa, turn on the RF power supply with a power of 200W to ionize the gas in the vacuum heat treatment furnace to generate plasma, and cool and take out after treating for 0.5h.

[0029] After testing, the target material has a cerium content of 99.99wt%, an average oxygen content of 350ppm, and a density of 6.74g / cm 3 , the average density is 99.85%. Figure 1 From the SEM test image, it can be seen that the surface of the target material is relatively flat and the particle size is uniform and dense.

[0030] Example 2

[0031] A method for preparing a cerium target material comprises the following steps: placing a block of cerium with a purity of 99.993 wt% into a water-cooled crucible of a suspension smelting furnace, repeatedly smelting twice in an argon atmosphere and then pouring out, adding a block of cerium with a purity of 99.993 wt% into the water-cooled crucible, smelting in an argon atmosphere, controlling the pressure in the suspension smelting furnace to be higher than the atmospheric pressure by 500 Pa, until the block of cerium is smelted into a cerium melt; pulling down the water-cooled crucible containing the cerium melt at a speed of 1 mm / min, and while the cerium melt is gradually cooled and solidified during the pulling down process, ultrasonic treatment is performed on the cerium melt to refine the grains to obtain a cerium ingot; wherein the frequency of the ultrasonic wave is 40 kHz, and the power of the ultrasonic instrument is 40 kW; after the cerium ingot is cooled to room temperature, it is placed in a vacuum heat treatment furnace, and evacuated to 1×10 -4 Pa, the temperature was raised to 400℃ and kept for 3h, and then cooled with the furnace; a two-roll mill was used to cold-roll the product to a thickness of 10mm to obtain a cold-rolled product; the cold-rolled product was cut into discs with a diameter of 50mm; the disc cerium target was placed in a vacuum heat treatment furnace and evacuated to 1×10 -4 Pa and then heated to 500 °C and immediately placed in cooling oil for cooling. Then placed in a vacuum heat treatment furnace and evacuated to 1 × 10 2 Pa and then heated to 150℃ and kept warm for 3h; the vacuum degree was maintained at 1×10 2 Pa, argon and hydrogen are introduced at a flow ratio of 2:1, and the hydrogen gas flow rate is 500sccm; heat to 500°C, adjust the gas flow rate to maintain the gas pressure at 1000Pa in the vacuum heat treatment furnace, turn on the RF power supply with a power of 200W to ionize the gas in the vacuum heat treatment furnace to generate plasma, and cool and take out after treating for 1h.

[0032] After testing, the target material has a cerium content of 99.993wt%, an average oxygen content of 180ppm, and a density of 6.748g / cm 3 , the average density is 99.93%.

[0033] Example 3

[0034] A method for preparing a cerium target material comprises the following steps: placing a cerium wire with a purity of 99.995wt% into a water-cooled crucible of a suspension smelting furnace, repeatedly smelting for three times in an argon atmosphere and then pouring out the cerium wire; adding a cerium wire with a purity of 99.995wt% into the water-cooled crucible, smelting in an argon atmosphere, controlling the pressure in the suspension smelting furnace to be higher than the atmospheric pressure by 400Pa until the cerium wire is smelted into a cerium melt; pulling down the water-cooled crucible containing the cerium melt at a speed of 0.5mm / min, and performing ultrasonic treatment on the cerium melt to refine the grains during the pulling down process to obtain a cerium ingot; wherein the frequency of the ultrasonic wave is 30kHz, and the power of the ultrasonic instrument is 30kW; after the cerium ingot cools to room temperature, placing it in a vacuum heat treatment furnace, and evacuating to 1×10 -3 Pa, the temperature was raised to 350℃ and kept for 2.5h, and then cooled with the furnace; a two-roll mill was used to cold-roll the product to a thickness of 5mm to obtain a cold-rolled product; the cold-rolled product was cut into discs with a diameter of 20mm; the disc cerium target was placed in a vacuum heat treatment furnace and evacuated to 1×10 -2 Pa and then heated to 450 °C and immediately placed in cooling oil for cooling. Then placed in a vacuum heat treatment furnace and evacuated to 1 × 10 1 Pa, then heat to 150℃ and keep warm for 2h; continue to evacuate to 1Pa, then introduce argon and hydrogen at a flow ratio of 5:1, and the hydrogen gas flow rate is 300sccm; heat to 500℃, adjust the gas flow rate to keep the gas pressure in the vacuum heat treatment furnace at 700Pa, turn on the RF power supply with a power of 200W to ionize the gas in the vacuum heat treatment furnace to generate plasma, and cool and take out after treating for 0.5h.

[0035] After testing, the target material has a cerium content of 99.995wt%, an average oxygen content of 230ppm, and a density of 6.743g / cm 3 , the average density is 99.89%.

[0036] Example 4

[0037] A method for preparing a cerium target material comprises the following steps: placing cerium particles with a purity of 99.99wt% into a water-cooled crucible of a suspension smelting furnace, repeatedly smelting for three times in an argon atmosphere and then pouring out, adding cerium particles with a purity of 99.99wt% into the water-cooled crucible, smelting in an argon atmosphere, controlling the pressure in the suspension smelting furnace to be higher than the atmospheric pressure by 400Pa, until the cerium particles are smelted into a cerium melt; pulling down the water-cooled crucible containing the cerium melt at a speed of 0.5mm / min, and performing ultrasonic treatment on the cerium melt to refine the grains while the cerium melt is gradually cooled and solidified during the pulling down process, so as to obtain a cerium ingot; wherein the frequency of the ultrasonic wave is 30kHz, and the power of the ultrasonic instrument is 30kW; after the cerium ingot is cooled to room temperature, placing it in a vacuum heat treatment furnace, and evacuating to 1×10 -4 Pa, the temperature was raised to 350℃ and kept for 2.5h, and then cooled with the furnace; a two-roll mill was used to cold-roll the product to a thickness of 5mm to obtain a cold-rolled product; the cold-rolled product was cut into discs with a diameter of 20mm; the disc cerium target was placed in a vacuum heat treatment furnace and evacuated to 1×10 -4 Pa and then heated to 500 °C and immediately placed in cooling oil for cooling. Then placed in a vacuum heat treatment furnace and evacuated to 1 × 10 -1 Pa, then heat to 100°C and keep it for 2h, then heat to 150°C and keep it for 1h; continue to evacuate to 1Pa, then introduce argon and hydrogen at a flow ratio of 10:1, and the hydrogen gas flow rate is 500sccm; heat to 500°C, adjust the gas flow rate to keep the gas pressure in the vacuum heat treatment furnace at 1000Pa, turn on the RF power supply with a power of 200W to ionize the gas in the vacuum heat treatment furnace to generate plasma, and cool and take out after treating for 0.5h.

[0038] After testing, the target material has a cerium content of 99.99wt%, an average oxygen content of 200ppm, and a density of 6.745g / cm 3 , the average density is 99.94%.

[0039] Comparative Example 1

[0040] A method for preparing a cerium target material comprises the following steps: placing block cerium with a purity of 99wt% into a water-cooled crucible of a suspension smelting furnace, smelting in an argon atmosphere, controlling the pressure in the suspension smelting furnace to be 400Pa higher than the atmospheric pressure, until the block cerium is smelted into a cerium melt; directly casting the cerium melt in the water-cooled crucible into a shape, and cooling the cerium melt to room temperature with the furnace to form a cerium ingot; cold rolling the cerium melt to a thickness of 5mm using a two-roll rolling mill to obtain a cold-rolled product; and cutting the cold-rolled product into a disc with a diameter of 20mm, which is the cerium target material.

[0041] After testing, the target material has a cerium content of 99wt%, an average oxygen content of 620ppm, and a density of 6.724g / cm 3, the average density is 98.64%.

[0042] Comparative Example 2

[0043] A method for preparing a cerium target material comprises the following steps: placing a cerium wire with a purity of 99.99wt% into a water-cooled crucible of a suspension smelting furnace, repeatedly smelting for three times in an argon atmosphere and then pouring out the cerium wire; adding a cerium wire with a purity of 99.99wt% into the water-cooled crucible, smelting in an argon atmosphere, controlling the pressure in the suspension smelting furnace to be higher than the atmospheric pressure by 400Pa until the cerium wire is smelted into a cerium melt; pulling down the water-cooled crucible containing the cerium melt at a speed of 2mm / min, and during the pulling down process, the cerium melt is gradually cooled and solidified to obtain a cerium ingot; after the cerium ingot cools to room temperature, placing it in a vacuum heat treatment furnace, and evacuating to 1×10 -3 Pa, the temperature was raised to 350℃ and kept for 2.5h, and then cooled with the furnace; a two-roll mill was used to cold-roll the product to a thickness of 5mm to obtain a cold-rolled product; the cold-rolled product was cut into discs with a diameter of 20mm; the disc cerium target was placed in a vacuum heat treatment furnace and evacuated to 1×10 1 Pa and then heated to 150°C and kept warm for 2h to obtain the cerium target.

[0044] After testing, the target material has a cerium content of 99.99wt%, an average oxygen content of 540ppm, and a density of 6.73g / cm 3 , the average density is 99.1%.

[0045] Comparative Example 3

[0046] A method for preparing a cerium target material comprises the following steps: placing a cerium wire with a purity of 99.99wt% into a water-cooled crucible of a suspension smelting furnace, repeatedly smelting for three times in an argon atmosphere and then pouring out the cerium wire; adding a cerium wire with a purity of 99.99wt% into the water-cooled crucible, smelting in an argon atmosphere, controlling the pressure in the suspension smelting furnace to be higher than the atmospheric pressure by 400Pa until the cerium wire is smelted into a cerium melt; pulling down the water-cooled crucible containing the cerium melt at a speed of 0.5mm / min, and performing ultrasonic treatment on the cerium melt to refine the grains during the pulling down process to obtain a cerium ingot; wherein the frequency of the ultrasonic wave is 30kHz, and the power of the ultrasonic instrument is 30kW; after the cerium ingot cools to room temperature, placing it in a vacuum heat treatment furnace, and evacuating to 1×10 -3 Pa, the temperature was raised to 350℃ and kept for 2.5h, and then cooled with the furnace; a two-roll mill was used to cold-roll the product to a thickness of 5mm to obtain a cold-rolled product; the cold-rolled product was cut into discs with a diameter of 20mm; the disc cerium target was placed in a vacuum heat treatment furnace and evacuated to 1×10 -2 Pa and then heated to 550 °C and immediately placed in cooling oil for cooling. Then placed in a vacuum heat treatment furnace and evacuated to 1 × 10 1Pa, then heat to 250℃ and keep warm for 2h; continue to evacuate to 1Pa and then introduce argon at a flow rate of 300sccm; heat to 500℃, adjust the gas flow rate to keep the gas pressure in the vacuum heat treatment furnace at 700Pa, turn on the RF power supply with a power of 200W to ionize the gas in the vacuum heat treatment furnace to generate plasma, and cool and take out after treating for 0.5h.

[0047] After testing, the target material has a cerium content of 99.99wt%, an average oxygen content of 510ppm, and a density of 6.74g / cm 3 , the average density is 99.82%.

[0048] Comparative Example 4

[0049] A method for preparing a cerium target material comprises the following steps: placing a cerium wire with a purity of 99.995wt% into a water-cooled crucible of a suspension smelting furnace, repeatedly smelting for three times in an argon atmosphere and then pouring out the cerium wire; adding a cerium wire with a purity of 99.995wt% into the water-cooled crucible, smelting in an argon atmosphere, controlling the pressure in the suspension smelting furnace to be higher than the atmospheric pressure by 400Pa until the cerium wire is smelted into a cerium melt; pulling down the water-cooled crucible containing the cerium melt at a speed of 0.5mm / min, and performing ultrasonic treatment on the cerium melt to refine the grains during the pulling down process to obtain a cerium ingot; wherein the frequency of the ultrasonic wave is 30kHz, and the power of the ultrasonic instrument is 30kW; after the cerium ingot cools to room temperature, placing it in a vacuum heat treatment furnace, and evacuating to 1×10 -3 Pa, the temperature was raised to 350℃ and kept for 2.5h, and then cooled with the furnace; a two-roll mill was used to cold-roll the product to a thickness of 5mm to obtain a cold-rolled product; the cold-rolled product was cut into discs with a diameter of 20mm; the disc cerium target was placed in a vacuum heat treatment furnace and evacuated to 1×10 -2 Pa and then heated to 450 °C and immediately placed in cooling oil for cooling. Then placed in a vacuum heat treatment furnace and evacuated to 1 × 10 1 Pa, then heat to 150℃ and keep warm for 2h; continue to evacuate to 1Pa, then introduce argon and hydrogen at a flow ratio of 5:1, with a hydrogen gas flow rate of 300sccm; heat to 250℃, turn on the RF power with a power of 200W to ionize the gas in the vacuum heat treatment furnace to generate plasma, and cool and take out after treating for 0.5h.

[0050] After testing, the target material has a cerium content of 99.995wt%, an average oxygen content of 410ppm, and a density of 6.745g / cm 3 , the average density is 99.91%.

[0051] After testing the cerium target in an aging box, it was found that the cerium target in the embodiment had no obvious change in appearance after being aged at 80°C for 5 days. It was found that the oxygen content in the cerium target had no obvious change. Although the cerium target in the comparative example also had no obvious change in appearance, it was found that a small amount of cerium oxide had appeared on the surface of the target. It can be seen that the cerium target provided by the present invention can greatly improve the antioxidant properties of the metal cerium target, and can be directly used for sputtering coating after long-term storage. From the test results in the above embodiments and comparative examples, it can be seen that the cerium target provided by the present invention has good antioxidant properties and storage stability, and can meet market requirements.

[0052] A rare earth target material and its preparation method are described in detail above. The above content is a further detailed description of the present invention in combination with a specific preferred embodiment. It cannot be determined that the specific implementation of the present invention is limited to these descriptions. For ordinary technicians in the technical field to which the present invention belongs, without departing from the concept of the present invention, its architecture can be flexible and can derive a series of products. Just making a few simple deductions or substitutions should be regarded as belonging to the scope of patent protection of the present invention determined by the submitted claims.

Claims

1. A method for preparing a rare earth target, wherein the rare earth is cerium, characterized in that: The steps include: (1) Weigh a certain amount of high-purity metallic cerium; (2) using a water-cooled crucible suspension smelting method to smelt the weighed metallic cerium into a cerium melt; (3) pulling down the cerium melt to form an ingot to obtain a metal cerium ingot, and rolling and cutting the obtained metal cerium ingot; (4) heat treating the cut cerium ingot; (5) subjecting the cerium target material after heat treatment and cooling to hydrogen plasma treatment; Step (2) before smelting, raw materials of the same composition are repeatedly smelted in a water-cooled crucible to clean the crucible; argon gas is passed during the smelting process to avoid oxidation; The step (3) of pulling down the ingot specifically comprises: while the cerium melt is gradually cooled and solidified during the pulling down process, ultrasonic treatment is performed on the cerium melt to refine the grains; The heat treatment in step (4) is carried out by sequentially quenching and tempering in an argon atmosphere; The hydrogen plasma treatment in step (5) is specifically as follows: placing the cerium target material after heat treatment and cooling in a vacuum heat treatment furnace, and evacuating the vacuum to 1×10 -1 Pa~1×10 2 Pa, introduce argon and hydrogen at a flow ratio of 2 to 10:1; heat to 300 to 500°C, adjust the gas flow rate to keep the gas pressure in the vacuum heat treatment furnace at 500 to 1000Pa, turn on the radio frequency power supply with a power of 200W to ionize the gas in the vacuum heat treatment furnace to generate plasma, treat for 0.5 to 1h, and then cool and take out.

2. The preparation method according to claim 1, characterized in that: The pressure in the suspension smelting furnace is 300 to 500 Pa higher than the atmospheric pressure.

3. The preparation method according to claim 1, characterized in that: The step (3) of pulling down the ingot is as follows: pulling down a water-cooled crucible containing molten cerium at a speed of 0.1-1 mm / min, thereby obtaining a cerium ingot; wherein the frequency of the ultrasonic wave is 20 kHz-40 kHz, and the power of the ultrasonic instrument is 20 kW-40 kW.

4. The preparation method according to claim 1, characterized in that: The rolling and cutting process in step (3) is as follows: after the metal cerium ingot cools to room temperature, it is placed in a vacuum heat treatment furnace and evacuated to 1×10 -1 Pa~1×10 -4 After Pa, the temperature is raised to 330℃~400℃ and kept for 2~3h, and then cooled with the furnace; a two-roll rolling mill is used to cold-roll the product to the required thickness to obtain a cold-rolled product; the cold-rolled product is cut into the required target size.

5. The preparation method according to claim 1, characterized in that: The heat treatment in step (4) is carried out in a manner of quenching and tempering in sequence under an argon atmosphere, specifically, placing the cut cerium ingot in a vacuum heat treatment furnace and evacuating the vacuum to 1×10 -1 Pa~1×10 -4 Pa, and then heated to 400℃~500℃, and then immediately placed in cooling oil for cooling, and then placed in a vacuum heat treatment furnace, and evacuated to 1×10 -1 Pa~1×10 2 After that, heat up to 100℃~150℃ and keep warm for 1~3h.

6. The preparation method according to claim 1, characterized in that: The preparation method of the rare earth target comprises the following steps: placing block cerium with a purity of 99.99wt% into a water-cooled crucible of a suspension smelting furnace, repeatedly smelting for three times under an argon atmosphere and then pouring out, adding block cerium with a purity of 99.99wt% into the water-cooled crucible, smelting under an argon atmosphere, controlling the pressure in the suspension smelting furnace to be higher than the atmospheric pressure by 400Pa, until the block cerium is smelted into a cerium melt; pulling down the water-cooled crucible containing the cerium melt at a speed of 0.1-1mm / min, and performing ultrasonic treatment on the cerium melt during the pulling down process to refine the grains while gradually cooling and solidifying the cerium melt to obtain a cerium ingot; wherein the frequency of the ultrasonic wave is 30kHz, and the power of the ultrasonic instrument is 30kW; after the cerium ingot cools to room temperature, placing it in a vacuum heat treatment furnace, and evacuating to 1×10 -4 Pa, the temperature was raised to 400℃ and kept for 2h, and then cooled with the furnace; a two-roll mill was used to cold-roll the product to 5mm to obtain a cold-rolled product; the cold-rolled product was cut into discs with a diameter of 5cm; the disc cerium target was placed in a vacuum heat treatment furnace and evacuated to 1×10 -4 Pa and then heated to 500 °C and immediately placed in cooling oil for cooling. Then placed in a vacuum heat treatment furnace and evacuated to 1 × 10 2 Pa, then heat to 150℃ and keep warm for 1h; continue to evacuate to 1×10 -1 Pa, argon and hydrogen are introduced at a flow ratio of 10:1; heated to 450°C, the gas flow rate is adjusted to make the gas pressure in the vacuum heat treatment furnace 1000Pa, and the radio frequency power supply is turned on with a power of 200W to ionize the gas in the vacuum heat treatment furnace to generate plasma. After treating for 1 hour, it is cooled and taken out.

7. The rare earth cerium target according to claim 6, characterized in that: The thickness of the cerium target is 1-10 mm.

8. The rare earth cerium target according to claim 6, characterized in that: The cerium content in the target material is ≥99.99wt%, the density of the target material is >98%, the oxygen content in the target material is <500ppm, and the average grain size of the rare earth target material is ≤100μm.

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