An anti-oxidation protective layer for high-temperature thin film sensor and preparation method thereof

Abstract

The present invention belongs to the field of thin film sensor technology and discloses an anti-oxidation protective layer for high-temperature thin film sensors and a preparation method thereof. The anti-oxidation protective layer comprises, from bottom to top, an Al2O3 insulating layer, a rare earth element RE-doped HfB2-MoSi2 thin film, and an outermost Al2O3 thin film. The rare earth element RE-doped HfB2-MoSi2 thin film is a composite material of HfB2 and MoSi2 doped with the rare earth element RE. By improving the structure and composition of the anti-oxidation protective layer, the resulting anti-oxidation protective layer for high-temperature thin film sensors can utilize multiple glass phases, such as silicates and borates, generated by the RE-doped HfB2-MoSi2 material at high temperatures. This layer possesses excellent self-healing capabilities, thereby repairing defects such as microcracks generated in the device under high-temperature aerobic conditions, improving overall device performance and lifespan. The layer can provide anti-oxidation protection for thin film sensors in high-temperature aerobic environments of 1100°C to 1800°C.

Description

Technical Field

[0001] The present invention belongs to the technical field of thin film sensors, and more specifically, relates to an anti-oxidation protective layer for a high-temperature thin film sensor and a preparation method thereof. Background Art

[0002] In recent years, harsh environments such as high temperature, high pressure and high-speed fluid impact have placed increasingly higher requirements on thin-film sensors. For example, hot-end devices such as the inner wall surface of gun barrels, the inner wall surface of combustion chambers, high-speed train shafts, aircraft engine turbine blades, cutting tool surfaces, the top surface of internal combustion engine pistons and high-temperature gas inlets and outlets need to overcome extreme conditions to obtain the required data such as temperature and stress. Fast and accurate data acquisition can timely analyze the current working status of the device and prevent accidents; at the same time, it can reflect the correctness of theoretical simulations and optimize device design.

[0003] Traditional data acquisition requires cutting grooves in the device surface and attaching or embedding sensors within them. This installation method can damage the device structure, affecting its physical properties and field conditions, and even leading to device failure. Thin-film sensors, on the other hand, can be deposited directly on the device surface, minimizing the impact on the device's performance and preventing interference with physical fields such as thermal and airflow fields. Furthermore, their rapid response speed allows for timely reflection of the device's operating status, enabling real-time monitoring. Therefore, thin-film sensors hold great promise for application in aerospace hot-end components. However, the functional layer materials currently used in hot-end sensors, such as metals like NiCr, PtRh, WRe, and PdCr, and oxides like ITO, are susceptible to oxygen oxidation and cracking and delamination under harsh conditions such as high temperature and high pressure. This can lead to performance degradation or even failure, impacting accuracy and service life. While these sensor materials exhibit excellent stability under high-temperature, oxygen-free conditions, oxidation at high temperatures is often unavoidable because these sensors are typically used in oxygen-rich environments (such as air).

[0004] Therefore, for thin film sensors working in high temperature environments, it is very necessary to prepare a protective layer on its functional layer to improve the performance and service life of the sensor. The anti-oxidation protective layer material currently deposited on sensitive films is Al2O3 (that is, only a single Al2O3 protective layer is formed on the functional layer of the high-temperature thin film sensor). Al2O3 has the characteristics of high melting point, high electrical insulation performance, good thermal conductivity, excellent high-temperature stability, and low oxygen diffusion coefficient. However, when it serves in harsh environments such as high temperature and high pressure for a long time, it will cause thermal stress due to thermal mismatch, and eventually produce microcracks that cannot be self-repaired. These cracks and the defects originally existing therein will become paths for rapid oxygen diffusion, which will reduce its protective performance and make it unable to effectively protect the functional layer, resulting in sensor failure. The single-layer aluminum oxide film disclosed in Publication No. CN102212823A is used as a protective layer to improve its service life, but under long-term high-temperature working conditions, Al2O3 will cause its performance and service life to decline due to problems such as thermal mismatch. At the same time, the patent document with publication number CN106498355A discloses "Anti-oxidation composite protective layer for high-temperature thin film sensors and its manufacturing method". This invention patent is based on the insufficient performance of single-layer Al2O3 film, and prepares a composite protective layer combining BN-ZrB2-Al2O3, which improves its anti-oxidation performance to a certain extent. However, it still has problems such as thermal mismatch at high temperatures, which leads to the failure of the functional layer film. Summary of the Invention

[0005] In response to the above defects or improvement needs of the prior art, the purpose of the present invention is to provide an anti-oxidation protective layer for high-temperature thin film sensors and a preparation method thereof, wherein the structure and composition of the anti-oxidation protective layer are improved, and a "sandwich" structure is designed from bottom to top, which comprises an Al2O3 insulating layer film, a rare earth element RE (rare earth; such as La, etc.) doped HfB2-MoSi2 film, and an outermost Al2O3 film. The corresponding anti-oxidation protective layer of the high-temperature thin film sensor can utilize various glass phases such as silicates and borates generated by RE-doped HfB2-MoSi2 materials at high temperatures, so that the protective layer has good self-healing ability, thereby being able to repair defects such as microcracks generated in the device under high-temperature aerobic environment, thereby improving the overall device performance and life, and being able to provide anti-oxidation protection for the thin film sensor in a high-temperature aerobic environment of 1100℃-1800℃.

[0006] To achieve the above-mentioned objectives, according to one aspect of the present invention, an anti-oxidation protective layer for a high-temperature thin-film sensor is provided, characterized in that, from bottom to top, it comprises an Al2O3 insulating layer film, a rare earth element RE-doped HfB2-MoSi2 film, and an outermost Al2O3 film; wherein the rare earth element RE-doped HfB2-MoSi2 film is a composite material of HfB2 and MoSi2, and is doped with the rare earth element RE; the thickness of the Al2O3 insulating layer film is 1 to 1.5 μm, the thickness of the rare earth element RE-doped HfB2-MoSi2 film is 1 to 2 μm, and the thickness of the outermost Al2O3 film is 1 to 2 μm.

[0007] As a further preferred embodiment of the present invention, the rare earth element RE is specifically La, Nd, Gd, Eu or Dy; the rare earth element RE doped HfB2-MoSi2 film is formed by a composite of the following components in the following mass percentages:

[0008] The mass percentage of HfB2 is 63% to 78%,

[0009] The mass percentage of MoSi2 is 12% to 22%,

[0010] The mass percentage of REB6 is 10% to 15%;

[0011] Preferably, the rare earth element RE doped HfB2-MoSi2 film is a La doped HfB2-MoSi2 film; the La doped HfB2-MoSi2 film is formed by a composite of the following components in the following mass percentages:

[0012] The mass percentage of HfB2 is 63% to 78%,

[0013] The mass percentage of MoSi2 is 12% to 22%,

[0014] The mass percentage of LaB6 is 10% to 15%.

[0015] As a further preferred embodiment of the present invention, the rare earth element RE doped HfB2-MoSi2 thin film is formed by a physical vapor deposition method;

[0016] Preferably, it is formed by magnetron sputtering.

[0017] As a further preferred embodiment of the present invention, the Al2O3 insulating layer film, the rare earth element RE doped HfB2-MoSi2 film and the outermost Al2O3 film in the anti-oxidation protection layer are all formed by magnetron sputtering.

[0018] According to another aspect of the present invention, a method for preparing an anti-oxidation protective layer is provided, characterized in that it comprises the following steps:

[0019] (S1) Preparing an Al2O3 insulating layer film on the surface to be protected by magnetron sputtering: using a magnetron sputtering process, using high-purity Al with a purity of at least 99.99% as a target material, and the background vacuum of the sputtering chamber does not exceed 2*10 -3 After Pa, O2 and Ar are introduced into the chamber, wherein the O2 flow rate is 1-2 sccm, the Ar and O2 flow ratio is 23:1-24:1, the sputtering pressure is maintained at 0.35-0.55 Pa, the sputtering power is 150-200 W, and the sputtering time is controlled to obtain an Al2O3 insulating layer film with a thickness of 1-1.5 μm;

[0020] (S2) depositing a rare earth element RE-doped HfB2-MoSi2 film on the Al2O3 insulating layer film obtained in step (S1): using a magnetron sputtering process, updating the target material, and maintaining the vacuum degree of the sputtering chamber at a level not exceeding 8*10 -4 After Pa, Ar is introduced into the chamber with an Ar flow rate of 15-35 sccm, maintaining the sputtering pressure at 0.3-0.75 Pa, the sputtering power at 400-500 W, the substrate temperature at 300-550 ° C, the substrate bias at 50-100 V, and controlling the sputtering time to obtain a rare earth element RE-doped HfB2-MoSi2 film with a thickness of 1-2 μm;

[0021] Wherein, the target material is one or more targets containing HfB2, MoSi2, and REB6 components;

[0022] (S3) preparing an outermost Al2O3 film on the rare earth element RE-doped HfB2-MoSi2 film obtained in step (S2): using a magnetron sputtering process, using high-purity Al with a purity of at least 99.99% as a target material, and in a sputtering chamber with a background vacuum of no more than 2*10 -3 After 100 spm, O2 and Ar are introduced into the chamber, wherein the O2 flow rate is 1-2 sccm, the Ar and O2 flow ratio is 23:1-24:1, the sputtering pressure is maintained at 0.35-0.55 Pa, the sputtering power is 150-200 W, the substrate temperature is 300-500°C, and the sputtering time is controlled to obtain an outermost Al2O3 film with a thickness of 1-2 μm, thereby forming a stacked structure including, from bottom to top, an Al2O3 insulating layer film, a rare earth element RE-doped HfB2-MoSi2 film, and an outermost Al2O3 film;

[0023] (S4) Annealing: Annealing the laminated structure on the surface to be protected in a vacuum of no more than 1*10 -3The anti-oxidation protective layer is obtained by annealing at a temperature of 1000 to 1300° C. for 2 to 4 hours.

[0024] As a further preferred embodiment of the present invention, the rare earth element RE doped HfB2-MoSi2 film formed in step (S2) contains:

[0025] The mass percentage of HfB2 is 63% to 78%,

[0026] The mass percentage of MoSi2 is 12% to 22%,

[0027] The mass percentage of REB6 is 10% to 15%.

[0028] According to another aspect of the present invention, the present invention provides the use of the above-mentioned anti-oxidation protective layer as an anti-oxidation protective layer of a high-temperature thin film sensor, which can protect the device and inhibit oxidation under high temperature conditions of 1100°C-1800°C.

[0029] Through the above technical solutions conceived by the present invention, compared with the existing technology, the present invention utilizes the synergistic effect of rare earth element RE-doped silicate and borate glass phase generated at high temperatures of 1100-1800°C in a "sandwich" structure of an Al2O3 insulating layer film, a rare earth element RE-doped HfB2-MoSi2 film, and an outermost Al2O3 film from bottom to top. This can repair defects such as microcracks and holes generated in a high-temperature aerobic environment, effectively improving the oxygen diffusion barrier capacity of the protective layer film and reducing the thermal mismatch effect, thereby ensuring the stability, reliability and durability of the thin film sensor at high temperatures. The high-temperature thin film sensor with an anti-oxidation protective layer obtained based on the present invention (such as the ceramic substrate thin film sensor obtained in the examples below) has anti-oxidation self-repairing capabilities, can increase the upper limit temperature and life of thin film sensors used on hot end components of aircraft engines such as turbine blades, and has great practical application value.

[0030] Specifically, the present invention can achieve the following beneficial effects:

[0031] 1. This invention proposes a "sandwich" protective layer structure for high-temperature thin-film sensors. From bottom to top, it consists of an Al2O3 insulating layer, a rare earth element (RE)-doped HfB2-MoSi2 thin film, and an outermost Al2O3 thin film. The thermal expansion coefficient of the Al2O3 insulating layer is similar to that of the ceramic substrate or thermally grown Al2O3 layer and the functional layer material. This minimizes thermal mismatch and thermal stress at high temperatures, improving adhesion between the protective layer and the substrate. Furthermore, the high resistivity of Al2O3 prevents the protective layer from significantly interfering with the electrical signals of the functional layer, effectively preventing the overall protective layer from affecting sensor performance.

[0032] 2. The present invention uses rare earth elements doped on HfB2-MoSi2 to improve the oxidation resistance and service life of the protective layer film at high temperatures. The intermediate layer proposed in the present invention is a rare earth element RE-doped HfB2-MoSi2 film, which has excellent high-temperature oxidation resistance. On the one hand, HfB2 has a high melting point and thermal conductivity (which is beneficial for reducing thermal hysteresis), and its oxidation product HfO2 has a high melting point and a high phase transition temperature (HfO2 is 2052K). The mobility of oxygen ion vacancies and electron holes in the HfO2 solid is low. On the other hand, the introduction of MoSi2 leads to the formation of SiO2 and a silicate glass phase. SiO2 can further restrict oxygen diffusion and reduce the oxygen partial pressure. The silicate glass phase with high viscosity, high melting point, low oxygen diffusion rate, and low vapor pressure formed at high temperature can cover the material, fill microcracks and holes caused by the volatilization of substances such as B2O3 at high temperatures, and prevent further oxygen intrusion. HfO2 reacts with SiO2 to form HfSiO4. The pinning effect of HfSiO4 and HfO2 prevents crack propagation in the glass phase during thermal shock, further improving stability. The integrity of the glass phase, in turn, inhibits borate evaporation and the escape of gaseous byproducts from the active oxidation of the inner coating, resulting in excellent high-temperature stability and self-healing capabilities. Finally, the doping of rare earth elements (RE) results in the formation of RE2Hf2O7 (e.g., La2Hf2O7) with a pyrochlore structure at high temperatures. The partial consumption of HfO2 mitigates the thermal mismatch effect caused by the HfO2 phase transition (the volume change caused by the transition from tetragonal to monoclinic). For example, La2Hf2O7 has a high melting point and high melt viscosity, which can increase the viscosity of the glass phase, making the mixing of oxides and the glass phase more uniform, hindering oxygen diffusion, and effectively filling defects such as microcracks. La also promotes the formation of silicates such as La₂Si₂Oₐ. Borate and silicate glasses containing La exhibit a strong tendency to phase separate due to their immiscibility. This immiscibility further increases the viscosity of the glass phase, facilitating the filling of microcracks and reducing the oxygen diffusion rate, thus providing further protection. Other RE elements (e.g., Nd, Gd, Eu, or Dy) corresponding to RE₂Hf₂Oₐ, RE₂Si₂Oₐ, and RE borates also exhibit similar functions.

[0033] 3. The main function of the outermost Al2O3 layer proposed in the present invention is to reduce the internal oxygen partial pressure of the protective layer, significantly slow down the oxygen diffusion rate, inhibit the volatilization of gases such as B2O3 in the protective layer at high temperatures, and increase the service life of the protective layer and the thin film sensor.

[0034] 4. The "sandwich" protective layer structure proposed in this invention effectively fills microcracks and other defects at high temperatures due to the formation of a Si-Al-O glass phase at the interface between the Al2O3 layer and the rare earth element RE-doped HfB2-MoSi2 layer, forming a transition layer. This improves the interfacial bonding strength of the film, effectively enhancing the protective layer's antioxidant capacity and service life. Furthermore, the intermediate rare earth element RE-doped HfB2-MoSi2 layer, in conjunction with the upper and lower Al2O3 layers, can also prevent the negative impact of the reaction products of the intermediate rare earth element RE-doped HfB2-MoSi2 layer at high temperatures on the material to be protected. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 1 is a schematic diagram of the overall structure of a high-temperature thin film sensor with an anti-oxidation protective layer formed thereon, obtained in accordance with an embodiment. DETAILED DESCRIPTION

[0036] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely for the purpose of explaining the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

[0037] In general, the antioxidant protective layer for the high-temperature thin-film sensor of the present invention has a "sandwich" structure, consisting, from bottom to top, of an Al2O3 insulating layer, a rare-earth element (RE)-doped HfB2-MoSi2 film, and an outermost Al2O3 film. The Al2O3 insulating layer has a thickness of 1 to 1.5 μm, the RE-doped HfB2-MoSi2 film has a thickness of 1 to 2 μm, and the outermost Al2O3 film has a thickness of 1 to 2 μm. This "sandwich" structure can be applied to any surface requiring protection, such as the functional layer of a high-temperature thin-film sensor.

[0038] The following embodiments take the functional layer of the high-temperature thin film sensor as the Ir-IrRh40 thin film thermocouple positive and negative electrode functional layer film as an example. In addition to the Ir-IrRh40 thin film thermocouple positive and negative electrode functional layer film, it is also applicable to high-temperature films of other functional layer materials known in the prior art (such as metals such as NiCr, PtRh, WRe, PdCr, and oxides such as ITO).

[0039] Example 1

[0040] like Figure 1As shown in the figure, it is a schematic diagram of the structure of a high-temperature thin film sensor based on the anti-oxidation protective layer of the present invention provided in an embodiment, which includes, from bottom to top, a ceramic substrate, an Ir-IrRh40 thin film thermocouple positive and negative electrode functional layer film, an Al2O3 insulating layer film, a La-doped HfB2-MoSi2 film, and an outermost Al2O3 film.

[0041] The method for preparing the overall device specifically includes the following steps (wherein, steps 1 and 2 are based on the preparation of high-temperature thin film sensors known in the prior art and can be flexibly adjusted based on actual needs and with reference to the prior art):

[0042] Step 1. Surface treatment of alumina ceramic substrate: The polished alumina ceramic substrate was ultrasonically cleaned in acetone, anhydrous ethanol and deionized water for 20 minutes each to remove oil and other impurities on the surface of the ceramic substrate. It was then blown dry with a nitrogen gun to keep the substrate dry. The substrate was cleaned again with anhydrous ethanol before each coating.

[0043] Step 2: Preparation of Ir-IrRh40 thin film as the functional layer of thin film thermocouple: Using Ir target and IrRh40 (Ir:Rh = 60wt%:40wt%), Ir-IrRh40 thin film thermocouple was deposited on the alumina ceramic substrate cleaned in step 1 by radio frequency magnetron sputtering. The film was patterned by photolithography. The sputtering gas was high-purity Ar with an Ar flow rate of 30sccm and a background vacuum of 8*10 -4 Pa, maintaining the sputtering pressure at 0.6 Pa, the sputtering power at 250 W, the substrate temperature at room temperature, the substrate without bias, and controlling the sputtering time to obtain a 1 μm thick Ir-IrRh40 functional layer film.

[0044] Step 3: Preparation of insulating layer Al2O3 film: Reactive radio frequency magnetron sputtering is used, with high purity Al with a purity of at least 99.99% as the target material, and the background vacuum degree of the sputtering chamber is less than 2*10 -3 After Pa, O2 and Ar were introduced into the cavity, with an O2 flow rate of 1 sccm, an Ar and O2 flow ratio of 23:1, the sputtering pressure was maintained at 0.5 Pa, the sputtering power was 150 W, the substrate temperature was room temperature, the substrate had no bias, and the sputtering time was controlled to obtain a 1 μm thick Al2O3 insulating layer film covering the functional layer film.

[0045] Step 4. Preparation of La-doped HfB2-MoSi2 film: RF magnetron sputtering was used, with the target material being a LaB6 and MoSi2 embedded HfB2 target, where the mass percentage of HfB2 was 78%, the mass percentage of MoSi2 was 12%, and the mass percentage of LaB6 was 10%. The background vacuum of the sputtering chamber was maintained at 8*10 -4Pa, high-purity Ar (purity not less than 99.995%) was introduced into the cavity with an Ar flow rate of 20 sccm, the sputtering pressure was maintained at 0.6 Pa, the sputtering power was 400 W, the substrate temperature was 500 ° C, the substrate bias was 50 V, and the sputtering time was controlled to obtain a La-doped HfB2-MoSi2 film with a thickness of ~ 1.5 μm.

[0046] Step 5. Preparation of the outermost Al2O3 film: Reactive radio frequency magnetron sputtering is used, with high purity Al with a purity of at least 99.99% as the target material, and the background vacuum of the sputtering chamber is less than 2*10 -3 After Pa, O2 and Ar were introduced into the chamber, with an O2 flow rate of 1 sccm, an Ar and O2 flow ratio of 23:1, the sputtering pressure was maintained at 0.5 Pa, the sputtering power was 150 W, the substrate temperature was 500 ° C, the substrate had no bias, and the sputtering time was controlled to obtain an outermost Al2O3 film with a thickness of ~ 2 μm.

[0047] Step 6. Heat treatment of the prepared "sandwich" protective layer: Place the prepared protective layer in a vacuum annealing furnace and heat it at a vacuum degree of less than 1*10 -3 Pa and annealing at 1300° C. for 2 hours, thereby preparing a high-temperature thin-film thermocouple with an anti-oxidation protective layer.

[0048] Example 2

[0049] The only difference between this embodiment and embodiment 1 is the preparation of the La-doped HfB2-MoSi2 thin film (ie, step 4).

[0050] Radio frequency magnetron sputtering was used, and the target material was a LaB6 and MoSi2 embedded HfB2 target, where the mass percentage of HfB2 was 78%, the mass percentage of MoSi2 was 12%, and the mass percentage of LaB6 was 10%. The background vacuum of the sputtering chamber was maintained at 8*10 -4 Pa, high-purity Ar was introduced into the cavity with an Ar flow rate of 20 sccm, the sputtering pressure was maintained at 0.6 Pa, the sputtering power was 450 W, the substrate temperature was 500 ° C, the substrate bias was 50 V, and the sputtering time was controlled to obtain a La-doped HfB2-MoSi2 film with a thickness of ~ 1.5 μm.

[0051] Example 3

[0052] The only difference between this embodiment and embodiment 1 is the preparation of the La-doped HfB2-MoSi2 thin film (ie, step 4).

[0053] Radio frequency magnetron sputtering was used, and the target material was a LaB6 and MoSi2 embedded HfB2 target, where the mass percentage of HfB2 was 78%, the mass percentage of MoSi2 was 12%, and the mass percentage of LaB6 was 10%. The background vacuum of the sputtering chamber was maintained at 8*10 -4 Pa, high-purity Ar was introduced into the cavity with an Ar flow rate of 20 sccm, the sputtering pressure was maintained at 0.6 Pa, the sputtering power was 500 W, the substrate temperature was 500 ° C, the substrate bias was 50 V, and the sputtering time was controlled to obtain a La-doped HfB2-MoSi2 film with a thickness of ~ 1.5 μm.

[0054] Example 4

[0055] The only difference between this embodiment and embodiment 3 is that the preparation of the La-doped HfB2-MoSi2 thin film is changed to the preparation of the Nd-doped HfB2-MoSi2 thin film (ie, step 4).

[0056] Radio frequency magnetron sputtering was used, and the target material was HfB2 target embedded with NdB6 and MoSi2, where the mass percentage of HfB2 was 78%, the mass percentage of MoSi2 was 12%, and the mass percentage of NdB6 was 10%. The background vacuum of the sputtering chamber was maintained at 8*10 -4 Pa, high-purity Ar was introduced into the cavity with an Ar flow rate of 20 sccm, the sputtering pressure was maintained at 0.6 Pa, the sputtering power was 500 W, the substrate temperature was 500 ° C, the substrate bias was 50 V, and the sputtering time was controlled to obtain a Nd-doped HfB2-MoSi2 film with a thickness of ~1.5 μm.

[0057] Example 5

[0058] The only difference between this embodiment and embodiment 3 is that the preparation of the La-doped HfB2-MoSi2 thin film is changed to the preparation of the Gd-doped HfB2-MoSi2 thin film (ie, step 4).

[0059] Radio frequency magnetron sputtering was used, and the target material was HfB2 target embedded with GdB6 and MoSi2, where the mass percentage of HfB2 was 78%, the mass percentage of MoSi2 was 12%, and the mass percentage of GdB6 was 10%. The background vacuum of the sputtering chamber was maintained at 8*10 -4 Pa, high-purity Ar was introduced into the cavity with an Ar flow rate of 20 sccm, the sputtering pressure was maintained at 0.6 Pa, the sputtering power was 500 W, the substrate temperature was 500 ° C, the substrate bias was 50 V, and the sputtering time was controlled to obtain a Gd-doped HfB2-MoSi2 film with a thickness of ~1.5 μm.

[0060] Example 6

[0061] The only difference between this embodiment and embodiment 3 is that the preparation of the La-doped HfB2-MoSi2 thin film is changed to the preparation of the Eu-doped HfB2-MoSi2 thin film (ie, step 4).

[0062] Radio frequency magnetron sputtering is used, and the target material is HfB2 target embedded with EuB6 and MoSi2, of which the mass percentage of HfB2 is 78%, the mass percentage of MoSi2 is 12%, and the mass percentage of EuB6 is 10%. The background vacuum of the sputtering chamber is maintained at 8*10 -4 Pa, high-purity Ar was introduced into the cavity with an Ar flow rate of 20 sccm, the sputtering pressure was maintained at 0.6 Pa, the sputtering power was 500 W, the substrate temperature was 500 ° C, the substrate bias was 50 V, and the sputtering time was controlled to obtain a Eu-doped HfB2-MoSi2 film with a thickness of ~1.5 μm.

[0063] Example 7

[0064] The only difference between this embodiment and embodiment 3 is that the preparation of the La-doped HfB2-MoSi2 thin film is changed to the preparation of the Dy-doped HfB2-MoSi2 thin film (ie, step 4).

[0065] Radio frequency magnetron sputtering was used, and the target material was HfB2 target embedded with DyB6 and MoSi2, where the mass percentage of HfB2 was 78%, the mass percentage of MoSi2 was 12%, and the mass percentage of DyB6 was 10%. The background vacuum of the sputtering chamber was maintained at 8*10 -4 Pa, high-purity Ar was introduced into the cavity with an Ar flow rate of 20 sccm, the sputtering pressure was maintained at 0.6 Pa, the sputtering power was 500 W, the substrate temperature was 500 ° C, the substrate bias was 50 V, and the sputtering time was controlled to obtain a Dy-doped HfB2-MoSi2 film with a thickness of ~1.5 μm.

[0066] Example 8

[0067] The only difference between this embodiment and embodiment 3 is the preparation of the La-doped HfB2-MoSi2 thin film (ie, step 4).

[0068] Radio frequency magnetron sputtering is used, and the target material is LaB6 and MoSi2 embedded HfB2 target, of which the mass percentage of HfB2 is 63%, the mass percentage of MoSi2 is 22%, and the mass percentage of LaB6 is 15%. The background vacuum of the sputtering chamber is maintained at 8*10 -4 Pa, high-purity Ar was introduced into the cavity with an Ar flow rate of 20 sccm, the sputtering pressure was maintained at 0.6 Pa, the sputtering power was 500 W, the substrate temperature was 500 ° C, the substrate bias was 50 V, and the sputtering time was controlled to obtain a La-doped HfB2-MoSi2 film with a thickness of ~ 1.5 μm.

[0069] Example 9

[0070] The only difference between this embodiment and embodiment 3 is the preparation of the La-doped HfB2-MoSi2 thin film (ie, step 4).

[0071] Radio frequency magnetron sputtering is used, and the target material is LaB6 and MoSi2 embedded HfB2 target, of which the mass percentage of HfB2 is 63%, the mass percentage of MoSi2 is 22%, and the mass percentage of LaB6 is 15%. The background vacuum of the sputtering chamber is maintained at 8*10 -4 Pa, high-purity Ar was introduced into the cavity with an Ar flow rate of 20 sccm, the sputtering pressure was maintained at 0.6 Pa, the sputtering power was 500 W, the substrate temperature was 500 ° C, the substrate bias was 50 V, and the sputtering time was controlled to obtain a La-doped HfB2-MoSi2 film with a thickness of ~ 1 μm.

[0072] Example 10

[0073] The only difference between this embodiment and embodiment 3 is the preparation of the La-doped HfB2-MoSi2 thin film (ie, step 4).

[0074] Radio frequency magnetron sputtering is used, and the target material is LaB6 and MoSi2 embedded HfB2 target, of which the mass percentage of HfB2 is 63%, the mass percentage of MoSi2 is 22%, and the mass percentage of LaB6 is 15%. The background vacuum of the sputtering chamber is maintained at 8*10 -4 Pa, high-purity Ar was introduced into the cavity with an Ar flow rate of 20 sccm, the sputtering pressure was maintained at 0.6 Pa, the sputtering power was 500 W, the substrate temperature was 500 ° C, the substrate bias was 50 V, and the sputtering time was controlled to obtain a La-doped HfB2-MoSi2 film with a thickness of ~ 2 μm.

[0075] Example 11

[0076] The only difference between this embodiment and embodiment 3 is the preparation of the insulating layer Al2O3 film (ie, step 3).

[0077] Reactive radio frequency magnetron sputtering is used, with high purity Al with a purity of at least 99.99% as the target material, and the background vacuum degree of the sputtering chamber is less than 2*10 -3 After Pa, O2 and Ar were introduced into the cavity, with an O2 flow rate of 1 sccm, an Ar and O2 flow ratio of 23:1, the sputtering pressure was maintained at 0.5 Pa, the sputtering power was 150 W, the substrate temperature was room temperature, the substrate had no bias, and the sputtering time was controlled to obtain a 1.5 μm thick Al2O3 insulating layer film covering the functional layer film.

[0078] Example 12

[0079] The only difference between this embodiment and embodiment 3 is the preparation of the outermost Al2O3 film (ie, step 5).

[0080] Reactive radio frequency magnetron sputtering is used, with high purity Al with a purity of at least 99.99% as the target material, and the background vacuum degree of the sputtering chamber is less than 2*10 -3 After Pa, O2 and Ar were introduced into the chamber, with an O2 flow rate of 1 sccm and an Ar to O2 flow ratio of 23:1. The sputtering pressure was maintained at 0.5 Pa, the sputtering power was 150 W, the substrate temperature was 500 ° C, the substrate had no bias, and the sputtering time was controlled to obtain an outermost Al2O3 film with a thickness of ~1 μm.

[0081] The thin-film thermocouples with the anti-oxidation protective layer prepared in Examples 1-12 were subjected to high-temperature and normal-pressure stability tests in an air environment. The results showed that their maximum application temperatures could reach above 1700°C (they could all stably operate for at least 10 hours at 1700°C, and the maximum operating time limit has not yet been determined). The maximum application temperature of Examples 3-7 could even reach 1800°C (they could stably operate for at least 10 hours at 1800°C, and the maximum operating time limit has not yet been determined). In contrast, during the research and development process, the inventors of the present invention reproduced the thin-film thermocouple temperature sensors with only an Al2O3 protective layer in the prior art. These sensors had already failed at a high temperature of 1700°C (they could operate continuously for up to 8 hours in the temperature range of 300°C to 1000°C; for example, the related prior art can be found in CN103266320A, in which a Pt-ITO thin-film thermocouple made with a single Al2O3 protective layer structure could only operate continuously for 8 hours in the temperature range of 300°C to 1000°C). This is primarily because the thin-film thermocouple temperature sensor with an anti-oxidation protective layer, developed based on this invention, can generate multiple glass phases at high temperatures (e.g., 1800°C). The resulting self-healing effect effectively enhances the stability of the protective layer structure, ensuring the sensor can operate stably and continuously for over 10 hours at temperatures like 1800°C. Furthermore, this "sandwich" protective layer effectively blocks the diffusion of oxygen atoms, ensuring the normal operation of the thin-film sensor at high temperatures.

[0082] The above embodiments are merely examples. For example, in the preparation of La-doped HfB2-MoSi2 thin films, in addition to using an HfB2 target inlaid with LaB6 and MoSi2, an HfB2 target with La and MoSi2 alternately and symmetrically attached to its surface can also be used (the attachment area ratio can be determined by calculation), or multiple targets can be used (the proportion of each target element in the film can be controlled by the deposition rate). As long as the resulting La-doped HfB2-MoSi2 thin film corresponds to a composite material of HfB2 and MoSi2 and contains the doped La element, the target film can specifically include the following components: HfB2 (preferably 63% to 78% by mass), MoSi2 (preferably 12% to 22% by mass), and LaB6 (preferably 10% to 15% by mass); the same applies to other RE element doping. For another example, in addition to magnetron sputtering, other thin film deposition processes known in the art can also be used (of course, these thin film deposition processes must not negatively impact the high-temperature thin film sensor itself), such as evaporation and other physical vapor deposition methods.

[0083] It will be easily understood by those skilled in the art that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. An anti-oxidation protective layer for a high-temperature thin film sensor, characterized in that: From bottom to top, it includes an Al2O3 insulating layer film, a rare earth element RE-doped HfB2-MoSi2 film, and an outermost Al2O3 film; wherein the rare earth element RE-doped HfB2-MoSi2 film is a composite material of HfB2 and MoSi2, and is doped with rare earth element RE; the thickness of the Al2O3 insulating layer film is 1 to 1.5 μm, the thickness of the rare earth element RE-doped HfB2-MoSi2 film is 1 to 2 μm, and the thickness of the outermost Al2O3 film is 1 to 2 μm.

2. The anti-oxidation protective layer according to claim 1, wherein: The rare earth element RE is specifically La, Nd, Gd, Eu or Dy; the rare earth element RE doped HfB2-MoSi2 film is formed by a composite of the following components in the following mass percentages: The mass percentage of HfB2 is 63% to 78%, The mass percentage of MoSi2 is 12% to 22%, The mass percentage of REB6 is 10% to 15%.

3. The anti-oxidation protective layer according to claim 1, wherein: The rare earth element RE doped HfB2-MoSi2 film is a La doped HfB2-MoSi2 film; the La doped HfB2-MoSi2 film is formed by a composite of the following components in the following mass percentages: The mass percentage of HfB2 is 63% to 78%, The mass percentage of MoSi2 is 12% to 22%, The mass percentage of LaB6 is 10% to 15%.

4. The anti-oxidation protective layer according to claim 1, wherein: The rare earth element RE doped HfB2-MoSi2 thin film is formed by a physical vapor deposition method.

5. The anti-oxidation protective layer according to claim 4, characterized in that: The rare earth element RE doped HfB2-MoSi2 film is formed by magnetron sputtering.

6. The anti-oxidation protective layer according to claim 1, wherein: The Al2O3 insulating layer film, the rare earth element RE doped HfB2-MoSi2 film and the outermost Al2O3 film in the anti-oxidation protection layer are all formed by magnetron sputtering.

7. A method for preparing an antioxidant protective layer, characterized in that: The following steps are involved: (S1) Preparing an Al2O3 insulating layer film on the surface to be protected by magnetron sputtering: using a magnetron sputtering process, using high-purity Al with a purity of at least 99.99% as a target material, and the background vacuum of the sputtering chamber does not exceed 2*10 -3 After Pa, O2 and Ar are introduced into the chamber, wherein the O2 flow rate is 1-2 sccm, the Ar and O2 flow ratio is 23:1-24:1, the sputtering pressure is maintained at 0.35-0.55 Pa, the sputtering power is 150-200 W, and the sputtering time is controlled to obtain an Al2O3 insulating layer film with a thickness of 1-1.5 μm; (S2) depositing a rare earth element RE-doped HfB2-MoSi2 film on the Al2O3 insulating layer film obtained in step (S1): using a magnetron sputtering process, updating the target material, and maintaining the vacuum degree of the sputtering chamber at a level not exceeding 8*10 -4 After Pa, Ar is introduced into the chamber with an Ar flow rate of 15-35 sccm, maintaining the sputtering pressure at 0.3-0.75 Pa, the sputtering power at 400-500 W, the substrate temperature at 300-550 ° C, the substrate bias at 50-100 V, and controlling the sputtering time to obtain a rare earth element RE-doped HfB2-MoSi2 film with a thickness of 1-2 μm; Wherein, the target material is one or more targets containing HfB2, MoSi2, and REB6 components; (S3) preparing an outermost Al2O3 film on the rare earth element RE-doped HfB2-MoSi2 film obtained in step (S2): using a magnetron sputtering process, using high-purity Al with a purity of at least 99.99% as a target material, and in a sputtering chamber with a background vacuum of no more than 2*10 -3 After 100 spm, O2 and Ar are introduced into the chamber, wherein the O2 flow rate is 1-2 sccm, the Ar and O2 flow ratio is 23:1-24:1, the sputtering pressure is maintained at 0.35-0.55 Pa, the sputtering power is 150-200 W, the substrate temperature is 300-500°C, and the sputtering time is controlled to obtain an outermost Al2O3 film with a thickness of 1-2 μm, thereby forming a stacked structure including, from bottom to top, an Al2O3 insulating layer film, a rare earth element RE-doped HfB2-MoSi2 film, and an outermost Al2O3 film; (S4) Annealing: Annealing the laminated structure on the surface to be protected in a vacuum of no more than 1*10 -3 The anti-oxidation protective layer is obtained by annealing at a temperature of 1000 to 1300° C. for 2 to 4 hours.

8. The method for preparing an anti-oxidation protective layer according to claim 7, wherein: The rare earth element RE doped HfB2-MoSi2 film formed in step (S2) corresponds to: The mass percentage of HfB2 is 63% to 78%, The mass percentage of MoSi2 is 12% to 22%, The mass percentage of REB6 is 10% to 15%.

9. Use of the anti-oxidation protective layer according to any one of claims 1 to 6 as an anti-oxidation protective layer for a high-temperature thin film sensor can protect the device and inhibit oxidation under high temperature conditions of 1100°C to 1800°C.

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