High-temperature heat flux sensor based on chromium-doped indium oxide and preparation method thereof

Abstract

The invention discloses a chromium-doped indium oxide-based high-temperature heat flux sensor and a preparation method thereof, a screen printing technology is adopted, a slurry formula and printing process parameters are optimized, a thermopile structure is accurately formed on a high-temperature-resistant ceramic substrate, and then a thermopile and a thermal resistance layer are subjected to step-by-step high-temperature sintering treatment, so that the chromium-doped indium oxide-based high-temperature heat flux sensor is obtained. And firm combination between the thin film and the substrate and densification of a microstructure are ensured. The finally prepared sensor has excellent high-temperature oxidation resistance and long-term working stability, is stable and reliable in thermoelectric output signal, meets the strict requirements of aerospace, energy power and other fields on high-temperature heat flow measurement, is suitable for heat flow monitoring in high-temperature combustion environments, high-speed pneumatic heating and other scenes, and has wide application prospects. And a reliable test means is provided for design and performance evaluation of the thermal protection system in an extreme environment.

Description

Technical Field

[0001] This invention belongs to the field of sensor technology, specifically relating to a high-temperature heat flux sensor based on chromium-doped indium oxide and its fabrication method. Background Technology

[0002] High-temperature heat flux sensors are key devices for measuring heat flux density under extreme environments, and have significant application value in aerospace, energy, and defense industries. Traditional heat flux sensors face three major technical bottlenecks: first, existing thermoelectric materials suffer severe oxidation and thermoelectric performance degradation at high temperatures; second, the interfacial stability between materials and electrodes is difficult to guarantee under high-temperature conditions; and third, the reliability and durability of sensors are insufficient under extreme thermal shock conditions. In particular, with the development of hypersonic vehicles and advanced aero-engines, there is an urgent need for heat flux sensors that can operate stably for extended periods above 1500℃, have fast response times, and high measurement accuracy.

[0003] Chromium oxide (Cr2O3) and indium oxide (In2O3) are highly resistant to high-temperature oxidation and chemical stability. Indium oxide (In2O3) has a high Seebeck coefficient. By modifying the thermoelectric properties of indium oxide with chromium doping, it can form a thermocouple with indium oxide, giving the thermopile ultra-high temperature resistance, which is an important way to break through the upper limit of the operating temperature of existing heat flow sensors. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a high-temperature heat flow sensor based on chromium-doped indium oxide and its preparation method, which overcomes the performance limitations of traditional thermoelectric materials in extreme high-temperature environments and fills the technical gap in the field of waterless ultra-high temperature measurement above 1500℃, thereby solving the technical problem of heat flow measurement at ultra-high temperatures.

[0005] The present invention adopts the following technical solution: A high-temperature heat flux sensor based on chromium-doped indium oxide includes a body 1. A second thin film layer and a third thin film layer are disposed on the body 1. The leads of the second thin film layer and the third thin film layer form a thermocouple pair and are arrayed to form a thermopile. A first thin film layer is disposed on the thermopile. The third thin film layer is a chromium-doped indium oxide thin film or an indium oxide thin film. The third thin film layer is an indium oxide thin film or a chromium-doped indium oxide thin film paired with the third thin film layer.

[0006] Preferably, the chromium doping concentration in chromium-doped indium oxide is such that the mass ratio of chromium oxide to indium oxide is 1%:1 to 10%:1.

[0007] Preferably, the thickness of the first thin film layer is 10~50μm.

[0008] Preferably, the first thin film layer is a high-temperature resistant insulating material.

[0009] Preferably, the thickness of the second and third thin film layers is 5~30 μm.

[0010] Preferably, the number of nodes formed by the second and third thin film layers is greater than or equal to 10.

[0011] Another technical solution of the present invention is a method for fabricating a high-temperature heat flux sensor based on chromium-doped indium oxide, comprising the following steps: Chromium-doped indium oxide powder and undoped indium oxide powder were respectively mixed with sintering aids and thickeners to prepare printing paste; Using printing paste, chromium-doped indium oxide thermocouple arms and undoped indium oxide thermocouple arms are sequentially deposited on the substrate through screen printing process. The printed body is then subjected to a first high-temperature sintering treatment in air, and then thermal resistance layers are deposited sequentially through a screen printing process. The body with the printed thermal resistance layer is subjected to a second high-temperature sintering process. A high-temperature stable electrode is connected to the sintered thermopile structure and then encapsulated in a high-temperature resistant package to obtain a high-temperature heat flow sensor based on chromium-doped indium oxide.

[0012] Preferably, the sintering temperature for the first and second high-temperature sintering treatments is 1450~1550℃, and the holding time is 0.5~2 hours.

[0013] Preferably, the high-temperature stable electrode is made of platinum, nickel-chromium, or nickel-silicon.

[0014] Another technical solution of the present invention is the application of a high-temperature heat flux sensor based on chromium-doped indium oxide in ultra-high temperature heat flux measurement.

[0015] Compared with the prior art, the present invention has at least the following beneficial effects: A high-temperature heat flux sensor based on chromium-doped indium oxide is proposed. By using an indium oxide-based material system, it overcomes the failure problem of traditional thermoelectric materials at high temperatures, enabling the sensor to operate stably for a long time in an oxidizing environment at 1500℃. The design based on the separation annealing process of thermoelectric stack and thermal resistance layer solves the problems of thermal stress matching and interface diffusion of multilayer thin films in high-temperature environments, providing a breakthrough technical solution for ultra-high temperature heat flux measurement in aerospace, advanced power and other fields.

[0016] Furthermore, the mass ratio of chromium oxide (Cr2O3) to indium oxide (In2O3) was controlled within the range of (1%~10%):1. This concentration range was experimentally verified: below 1%, the doping effect was not significant, and above 10% led to a deterioration in the conductivity of the material. The optimal doping ratio was around 5%, at which point the optimal band structure could be formed, achieving the maximum Seebeck coefficient while maintaining high conductivity.

[0017] Furthermore, the first thin film layer functions as a thermal resistance film. In order to ensure the stability of the sensor at high temperatures and avoid severe evaporation at high temperatures that could cause sensor failure, the film cannot be too thin. In addition, if the film is too thick, it will affect heat transfer. Therefore, the thickness of the first thin film layer needs to be set within a certain range of 10~50μm.

[0018] Furthermore, high-purity alumina is selected as the main material for the thermal resistance layer, which has excellent high-temperature insulation performance and thermal expansion matching. Silicon oxide (SiO2) or aluminum nitride (AlN) can also be used as alternative materials, but their temperature resistance is lower and the sintering process parameters need to be adjusted.

[0019] Furthermore, the thickness of the second and third thin film layers is set in the range of 5~30μm, with the core objective of achieving an optimal balance between sensitivity, response speed, and mechanical reliability. This thickness is thin enough to reduce thermal resistance and heat capacity, thereby improving sensor sensitivity and accelerating the response speed to changes in heat flow; at the same time, it is thick enough to ensure the mechanical strength of the thin film layers, making them less prone to damage during manufacturing and use, and ensuring the structural stability and long-term reliability of the sensor.

[0020] Furthermore, the second thin film layer (chromium-doped indium oxide) and the third thin film layer (undoped indium oxide) need to form at least 10 pairs of thermocouple nodes to generate sufficient thermoelectric potential signals. The number of nodes is proportional to the sensitivity, and the spacing between each node is controlled between 0.5 and 1 mm to ensure the uniformity of the thermal flow field and spatial resolution.

[0021] A method for fabricating a high-temperature heat flux sensor based on chromium-doped indium oxide (INO) optimizes high-temperature stability and thermoelectric performance through a specific material combination and layered sintering process. Chromium-doped INO and pure INO powder are separately slurried, ensuring excellent high-temperature stability and a low Seebeck coefficient in the thermocouple arm material, which is fundamental for generating effective thermoelectric signals at high temperatures. Screen printing is employed, which is low-cost, easy to pattern, and can accurately deposit complex thermopile structures. Two high-temperature sintering processes are used: the first sintering densifies the thermocouple arm and forms a stable structure, while the second sintering firmly bonds the thermal resistance layer, avoiding damage to the formed thermocouple arm from the first high-temperature sintering. High-temperature stable electrodes and encapsulation ensure long-term reliable operation of the sensor in extreme environments. The overall process balances high-temperature adaptability, structural reliability, and manufacturing feasibility.

[0022] Furthermore, the high-temperature sintering process must employ a programmable temperature-controlled furnace with a heating rate of 5-10℃ / min and a cooling rate of <5℃ / min to avoid thermal stress cracking. The second sintering process must maintain the same temperature profile as the first sintering process to ensure interlayer bonding strength.

[0023] Furthermore, ordinary metal electrodes can fail to maintain contact due to oxidation or diffusion. Using high-temperature electrodes and brazing to form a metallurgical bond establishes a stable ohmic contact, ensuring high-fidelity transmission of thermoelectric signals. Platinum wire (0.2mm in diameter) is the preferred electrode material due to its superior oxidation resistance at high temperatures. Nickel-chromium (NiCr) and nickel-silicon (NiSi) alloys can be used as low-cost alternatives, but their long-term operating temperature must be below 1300℃. Platinum adhesive is used for encapsulation to enhance high-temperature performance.

[0024] In summary, this invention solves the problems of material oxidation, thermoelectric performance degradation, and poor interface stability under high-temperature environments by pairing chromium-doped indium oxide with indium oxide to form thermocouple pairs, combined with a high-temperature resistant substrate and a thermal resistance layer structure. It has the advantages of excellent high-temperature resistance, high thermoelectric stability, and reliable measurement accuracy.

[0025] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the following description of the relative embodiments will be briefly introduced. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 This is an isometric view of the high-temperature heat flux sensor of the present invention; Figure 2 This is a top view schematic diagram of the high-temperature heat flux sensor of the present invention; Figure 3 This is a diagram showing the calibration results of the high-temperature heat flux sensor of this invention.

[0028] Figure 4 The graph shows the response time of the high-temperature heat flux sensor of this invention.

[0029] Wherein: 1. Body; 2. First thin film layer; 3. Second thin film layer; 4. Third thin film layer. Detailed Implementation

[0030] The technical solution of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0031] Unless otherwise specified, all embodiments and preferred embodiments mentioned herein can be combined to form new technical solutions.

[0032] Unless otherwise specified, all the technical features and preferred features mentioned herein can be combined to form new technical solutions.

[0033] In this invention, unless otherwise specified, percentage (%) or parts refer to weight percentage or parts relative to the composition.

[0034] Unless otherwise specified, the components or preferred components involved in this invention can be combined with each other to form new technical solutions.

[0035] In this invention, unless otherwise specified, the numerical range "a~b" represents an abbreviation of any combination of real numbers between a and b, where a and b are both real numbers. For example, the numerical range "6~22" means that all real numbers between "6~22" have been listed in this document, and "6~22" is simply an abbreviation of these numerical combinations.

[0036] The "scope" disclosed in this invention can be in the form of a lower limit and an upper limit, and can be one or more lower limits and one or more upper limits, respectively.

[0037] In this invention, the term "and / or" as used herein refers to any combination of one or more of the associated listed items, as well as all possible combinations, and includes such combinations.

[0038] In this invention, unless otherwise stated, the various reactions or operation steps may be performed sequentially or in a particular order. Preferably, the reaction methods described herein are performed sequentially.

[0039] Unless otherwise stated, the technical and scientific terms used herein have the same meanings as those familiar to those skilled in the art. Furthermore, any methods or materials similar to or equivalent to those described herein may also be used in this invention.

[0040] This invention provides a high-temperature heat flow sensor based on chromium-doped indium oxide (INO) and its fabrication method. Using INO as the key thermoelectric material, by controlling the doping concentration and distribution of chromium, acceptor levels and localized states are formed in the INO lattice, effectively regulating the carrier concentration and transport characteristics of the material, altering the Seebeck coefficient of INO, and maintaining excellent high-temperature stability. When paired with undoped INO to form a thermocouple, it exhibits significantly enhanced thermoelectric response performance, suitable for heat flow measurement in extreme high-temperature environments. The sensor is fabricated using screen printing technology. By optimizing the paste formulation and printing process parameters, the thermopile structure is precisely formed on a high-temperature resistant ceramic substrate. The thermopile and thermal resistance layer are then subjected to stepwise high-temperature sintering to ensure a strong bond between the thin film and the substrate and a dense microstructure. The final sensor exhibits excellent high-temperature oxidation resistance and long-term operational stability. Its thermoelectric output signal is stable and reliable, meeting the stringent requirements for high-temperature heat flow measurement in aerospace, energy and power fields. It is suitable for heat flow monitoring in high-temperature combustion environments, high-speed aerodynamic heating and other scenarios, providing a reliable testing method for the design and performance evaluation of thermal protection systems in extreme environments.

[0041] Please see Figure 1 and Figure 2 This invention discloses a high-temperature heat flux sensor based on chromium-doped indium oxide, comprising a body 1, a first thin film layer 2, a second thin film layer 3, and a third thin film layer 4. The body 1 is a high-temperature resistant substrate, on which the second thin film layer 3 and the third thin film layer 4 are disposed. The third thin film layer 3 is a chromium-doped indium oxide thin film or an indium oxide thin film, and the corresponding third thin film layer 4 is an indium oxide thin film or a chromium-doped indium oxide thin film paired with the third thin film layer 3. The leads of the second thin film layer 3 and the third thin film layer 4 form a thermocouple pair, which are arrayed to form a thermopile. The first thin film layer 2 is a thermal resistance layer film, disposed on the thermopile of the second thin film layer 3 and the third thin film layer 4.

[0042] The thickness of the first thin film layer 2 is 10~50μm, and the thickness of the second thin film layer 3 and the third thin film layer 4 is 5~30μm.

[0043] The number of nodes formed by the second thin film layer 3 and the third thin film layer 4 is greater than or equal to 10.

[0044] A thermocouple pair consisting of chromium-doped indium oxide thermoelectric material and undoped indium oxide. The Seebeck coefficient of chromium-doped indium oxide is changed by doping with chromium. The sensor is suitable for heat flow measurement in high-temperature environments.

[0045] The doping concentration of chromium in chromium-doped indium oxide is such that the mass ratio of chromium oxide to indium oxide ranges from 1%:1 to 10%:1.

[0046] The thermal resistance layer is made of high-temperature resistant insulating materials such as alumina.

[0047] The working principle of a high-temperature heat flux sensor based on chromium-doped indium oxide according to the present invention is as follows: When heat flows through the sensor's sensitive element via radiation, convection, or conduction, its unique structural design generates a significant temperature gradient distribution. The selective coverage of the thermal resistance layer maintains a lower temperature in the covered area, while the exposed area remains at a higher temperature. This temperature difference creates a distinct hot-cold node distribution in the thin-film thermopile: nodes shielded by the thermal resistance layer have lower temperatures, while those exposed to the heat flow have higher temperatures. Based on the Seebeck effect, these temperature differences accumulate in the loop, generating a measurable thermoelectric potential. Although the thermoelectric potential of a single node is small, the output signal can be effectively amplified through the series connection of numerous thermocouples and optimized thermal resistance layer thickness design. As the heat flow intensity increases, the temperature difference between the covered and uncovered areas increases linearly, leading to a corresponding increase in thermoelectric potential and a boost in the sensor's output signal. Using a pre-established calibration curve, the sensor's output voltage signal can be accurately converted into a corresponding heat flux density value.

[0048] This invention modifies the thermoelectric properties of materials through chromium doping technology. It effectively solves the problems of high-temperature oxidation and thermal stress matching through screen printing fabrication process and distributed annealing, enabling the sensor to maintain excellent measurement accuracy and stability in ultra-high temperature environments. The thin-film structure endows the sensor with rapid thermal response capability, which can accurately capture transient heat flow changes and withstand severe thermal shock. The related materials and devices provide reliable testing solutions for aerospace and other fields.

[0049] This invention discloses a method for fabricating a high-temperature heat flux sensor based on chromium-doped indium oxide, comprising the following steps: S1. Chromium-doped indium oxide powder and undoped indium oxide powder are respectively mixed with sintering aid and thickener to prepare printing paste; The sintering aid accounts for 5% to 30% of the mass of chromium-doped or undoped indium oxide, with a recommended value of 10%; the thickener accounts for 5% to 20% of the mass of chromium-doped or undoped indium oxide, with a recommended value of 5%.

[0050] High-melting-point glass powder was used as the sintering aid, and ethyl cellulose was selected as the thickener. A 150-mesh screen was used for screen printing, and the printing thickness was controlled at 15μm by adjusting the squeegee pressure and the screen mesh count.

[0051] S2. Chromium-doped indium oxide and undoped indium oxide thermocouple arms are sequentially deposited on a high-temperature resistant ceramic substrate by screen printing. S3. The printed substrate is subjected to a first high-temperature sintering treatment in air. The sintering temperature for the first high-temperature sintering treatment was 1450~1550℃, and the holding time was 0.5~2 hours.

[0052] S4. Thermal resistance layers are sequentially deposited on a high-temperature resistant ceramic substrate using a screen printing process. S5. The substrate with the printed thermal resistance layer is subjected to a second high-temperature sintering treatment in air, and a high-temperature stable electrode is connected to the sintered thermopile structure and high-temperature resistant encapsulation is performed.

[0053] The sintering temperature for the second high-temperature sintering treatment was 1450~1550℃, and the holding time was 0.5~2 hours.

[0054] The thermoelectric layer is printed using two or more printing processes, with each printing thickness of 5~15μm. The thermal resistance layer is printed using three or more printing processes, with each printing thickness of 5~15μm.

[0055] High-temperature stable electrodes are made of high-temperature resistant electrode materials such as platinum, nickel-chromium, and nickel-silicon.

[0056] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0057] In existing technologies, high-temperature heat flux sensors have long faced challenges such as material oxidation, thermoelectric performance degradation, and poor interface stability under high-temperature environments. Traditional metal thermocouple materials are prone to oxidation reactions at temperatures exceeding 1000℃, leading to drift or even failure of the thermoelectric output signal. Although traditional thermoelectric materials such as ITO have high Seebeck coefficients, their high-temperature stability is insufficient, making it difficult to maintain reliable measurement performance under extreme thermal shock conditions.

[0058] To address the aforementioned issues, researchers discovered that the crystal structure of indium oxide (IO) can be modulated by doping elements, thereby altering its Seebeck coefficient. Chromium exhibits a high lattice matching degree with IO, and its doping effectively suppresses the high-temperature oxidation process. Further research revealed that assembling chromium-doped IO with undoped IO into a thermocouple pair can generate a stable thermoelectric output signal. Based on this, constructing a thermopile by arraying thermocouple pairs and combining it with a high-temperature resistant substrate and a thermally resistive layer to isolate heat flow becomes a feasible path to achieve stable high-temperature measurements.

[0059] Therefore, this application proposes a technical solution comprising a high-temperature resistant substrate, a thermal resistance layer film, a chromium-doped indium oxide film, and a combination of indium oxide films. The thermal resistance layer film covers the substrate surface, and the chromium-doped indium oxide film and the indium oxide film are alternately arranged to form thermocouple pairs, and are arranged in an array to form a thermopile structure.

[0060] Among them, the high-temperature resistant substrate refers to a ceramic material that can withstand high-temperature thermal shock. Specifically, it can be made of alumina or zirconia ceramics, which is used to support the thin film layer and transfer heat flow.

[0061] A thermal resistance layer film is an insulating layer with high thermal resistance properties, which can be made of alumina material and is used to isolate heat conduction between the substrate and the thermopile.

[0062] Chromium-doped indium oxide thin films refer to indium oxide semiconductor materials modified with chromium, which can be achieved through solid-state sintering and used to form thermocouple pairs with undoped indium oxide.

[0063] Indium oxide thin films refer to undoped indium oxide semiconductor materials, which can be achieved through chemical vapor deposition. Their Seebeck coefficient differs from that of chromium-doped indium oxide, thus generating thermoelectric voltage.

[0064] A thermopile is an array structure consisting of multiple thermocouple pairs connected in series. It can be implemented using a screen printing process to amplify the thermoelectric output signal and improve measurement sensitivity.

[0065] Specifically, a high-temperature resistant substrate serves as the supporting structure, maintaining mechanical strength under high-temperature conditions. A thermal resistance thin film covers the substrate surface, reducing direct heat transfer to the thermocouple stack and thus establishing a stable temperature gradient. Chromium-doped indium oxide thin films are alternately deposited to form thermocouple arms; when heat flows onto the sensor, a thermoelectric potential difference is generated between the cold and hot ends of the thermocouple pair. The arrayed thermocouple stack superimposes the potentials of individual thermocouples, significantly improving the output signal strength.

[0066] Compared to existing technologies, traditional heat flux sensors mostly use metal thermocouple materials, which lack sufficient high-temperature oxidation resistance and exhibit a sharp decrease in thermoelectric coefficient with increasing temperature. This solution employs an all-oxide material system, where the difference in thermoelectric coefficients between chromium-doped indium oxide and indium oxide remains stable at high temperatures. Furthermore, the inherent oxidation resistance of oxide materials significantly extends the sensor's lifespan. In addition, the introduction of a thermal resistance layer effectively reduces the interference of substrate heat conduction on the temperature gradient distribution, improving measurement accuracy.

[0067] Through the above technical solutions, this application solves the problems of performance degradation of thermoelectric materials, poor interface stability, and large measurement errors caused by uneven heat flux distribution under high-temperature environments. The combination of high-temperature resistant substrate and thermal resistance layer effectively isolates external thermal shocks, the thermocouple pairs of chromium-doped indium oxide and indium oxide maintain a stable Seebeck coefficient difference at high temperatures, and the arrayed thermopile structure enhances the signal output strength, ultimately achieving reliable measurement of heat flux density under high-temperature environments.

[0068] This application further proposes a thermocouple pair consisting of a chromium-doped indium oxide thermoelectric material and an undoped indium oxide. The chromium-doped indium oxide changes its Seebeck coefficient through chromium doping, and the sensor is suitable for heat flow measurement in high-temperature environments.

[0069] Chromium-doped indium oxide (INO) thermoelectric materials refer to solid solutions formed by introducing chromium into the INO lattice. This can be achieved using sol-gel or solid-state sintering methods. Chromium doping regulates carrier concentration and suppresses high-temperature lattice vibrations, thereby improving the material's thermoelectric stability. Undoped INO refers to materials that maintain the intrinsic crystal structure of INO, achieved by controlling the sintering atmosphere to avoid introducing impurity elements. Undoped INO forms thermocouples with chromium-doped INO with significantly different Seebeck coefficients, resulting in stable thermoelectric potential output at high temperatures.

[0070] Specifically, chromium, in the form of trivalent ions, replaces indium sites in the indium oxide lattice, causing changes in the carrier concentration and mobility of the material, thereby modulating the Seebeck coefficient. When the two arms of the thermocouple pair are made of chromium-doped indium oxide and undoped indium oxide, respectively, a thermoelectric electromotive force is generated under the action of high-temperature heat flux. The amplitude of this electromotive force is linearly related to the heat flux density. Since both materials are metal oxide systems, they can maintain chemical stability in high-temperature oxidizing environments, avoiding the performance degradation caused by oxidation in traditional metal thermocouple materials.

[0071] Compared to existing technologies, traditional nickel-chromium / nickel-silicon thermocouples suffer severe oxidation above 800℃, leading to thermoelectric output drift. This solution utilizes an all-oxide thermocouple material, forming a dense oxide layer on the surface at high temperatures to prevent further oxidation. Simultaneously, by precisely controlling the Seebeck coefficient of indium oxide through chromium doping, it achieves thermoelectric properties that match those of undoped indium oxide, overcoming the low thermoelectric output of single-oxide materials.

[0072] Through the above technical solution, this application solves the problems of oxidation failure of thermoelectric materials and poor thermoelectric output stability under high temperature environments, and realizes accurate measurement of heat flux density above 1500℃. Chromium-doped indium oxide has a similar coefficient of thermal expansion to undoped indium oxide, and the interfacial stress is significantly reduced during thermal cycling, avoiding cracking failure at the connection between the thermocouple arm and the electrode, and extending the service life of the sensor.

[0073] This application further proposes the doping concentration of chromium in chromium-doped indium oxide, wherein the mass ratio of chromium oxide to indium oxide ranges from 1%:1 to 10%:1.

[0074] The chromium doping concentration refers to the doping ratio of chromium oxide in the indium oxide matrix, which can be achieved by adjusting the mixing ratio of chromium oxide and indium oxide in the precursor solution. This ratio directly affects the carrier concentration and lattice distortion within the material, thereby controlling the Seebeck coefficient and conductivity matching relationship. The mass ratio range refers to the range of chromium oxide to indium oxide mass ratios, which can be controlled by stoichiometry to regulate the decomposition and recombination reactions of the two oxides during sintering. This range ensures the uniform distribution of the dopant element in the matrix.

[0075] Specifically, when the mass ratio of chromium oxide to indium oxide is less than 1%, the modification effect of chromium on the indium oxide lattice is insufficient, making it difficult to effectively improve the thermoelectric potential output of the material. When the mass ratio exceeds 10%, excess chromium will form a second-phase precipitate, leading to increased grain boundary resistance and obstruction of thermoelectric transport channels. By controlling the mass ratio within the range of 1% to 10%, the synergistic effect of carrier concentration gradient and lattice scattering effect can be optimized while maintaining the stability of the indium oxide crystal structure. This allows the thermocouple to maintain a high Seebeck coefficient and possess good thermal shock resistance under high-temperature conditions.

[0076] Compared with existing technologies, traditional doping processes often employ fixed ratios or empirical proportions, without systematically studying the impact of doping concentration on high-temperature thermoelectric performance. For example, some schemes using trace doping below 1% result in insufficient thermoelectric response sensitivity of the material; while using excessive doping above 15%, the material is prone to delamination during thermal cycling. This scheme establishes a quantitative correlation between chromium doping concentration and high-temperature thermoelectric stability by limiting a specific mass ratio range.

[0077] Through the above technical solution, this application effectively solves the problem of material performance degradation caused by doping concentration mismatch under high temperature environment, so that the thermocouple pair can still maintain a stable Seebeck coefficient output above 1500℃, avoiding thin film cracking or interface peeling caused by excessive lattice distortion, thereby significantly improving the measurement accuracy and service life of the sensor.

[0078] This application further proposes that the material of the first thin film layer, namely the thermal resistance layer, is a high-temperature resistant insulating material such as alumina.

[0079] The thermal resistance layer is a functional layer placed between the substrate and the thermopile. It can be implemented using ceramic materials such as alumina. Its function is to create a temperature gradient through heat conduction while isolating heat flow interference between the substrate and the thermopile. The high-temperature resistant insulating material is a material that maintains its electrical insulation properties even at high temperatures. It can be implemented using ceramic materials such as alumina, zirconium oxide, or silicon nitride. Its function is to prevent leakage current at high temperatures and ensure the stability of the electrical signal output by the thermopile.

[0080] Specifically, the thermal resistance layer is deposited on a high-temperature resistant ceramic substrate using a screen printing process, forming a dense bond with the substrate during high-temperature sintering. Due to its high thermal conductivity and high resistivity, alumina effectively conducts heat and forms a stable temperature gradient at high temperatures, while simultaneously blocking the electrical conduction path between the substrate and the thermopile. Therefore, the thermal resistance layer not only provides a heat flow path for the thermopile but also prevents interference from the substrate material with the thermopile's output signal through its electrical insulation properties.

[0081] Compared to existing technologies, traditional heat flow sensors often use silicon oxide as the thermal resistance layer. Silicon oxide is prone to crystal transformation or interfacial reactions at high temperatures, leading to decreased thermal conductivity or evaporation failure. This solution uses alumina as the thermal resistance layer material, which exhibits significantly better high-temperature phase stability than silicon oxide, and its coefficient of thermal expansion is more compatible with the substrate material, effectively reducing the risk of interlayer cracking caused by high-temperature thermal stress.

[0082] Through the above technical solution, this application solves the technical problems of thermal resistance layer insulation failure and unstable thermal conduction under high temperature environment. By utilizing the high temperature stability and matching thermal expansion characteristics of alumina material, it ensures that the sensor can maintain a stable temperature gradient and electrical insulation performance under extreme temperature conditions, thereby improving the accuracy and long-term reliability of heat flow measurement.

[0083] This application further proposes that the number of nodes formed by the second and third thin film layers is at least 10.

[0084] The number of nodes refers to the number of connection points between the two different thermoelectric materials in a thermocouple pair, which can be achieved by arranging multiple thermocouple pairs in an array. In high-temperature heat flux sensors, increasing the number of nodes can improve the overall output signal strength of the thermopile, thereby enhancing the sensitivity to detecting subtle changes in heat flux.

[0085] The thermocouple pair consists of chromium-doped indium oxide and undoped indium oxide, specifically achieved by alternating printing of the two materials to form a series structure. By increasing the number of nodes, the thermoelectric potential superposition effect of the thermopile is significantly amplified, which is beneficial for obtaining a more stable measurement signal in high-temperature environments.

[0086] Specifically, multiple series-connected thermocouple pairs are formed by alternately depositing chromium-doped indium oxide (INO) and undoped INO films on a high-temperature ceramic substrate using a screen printing process. The cold and hot junctions of each thermocouple pair are connected by metal electrodes. When heat flux acts on the sensor, the thermoelectric potentials generated at each node are superimposed to form the total output signal. Increasing the number of nodes makes the linear relationship between signal strength and heat flux density more significant, while reducing the impact of environmental noise on the measurement results.

[0087] Compared to existing technologies, traditional heat flux sensors are susceptible to material property degradation and electromagnetic interference at high temperatures. This solution, by setting a minimum node count threshold, ensures that the thermopile can still output a sufficiently strong and effective signal at high temperatures, significantly improving the signal-to-noise ratio and measurement stability. Furthermore, the arrayed node design can disperse thermal stress, reducing the risk of structural failure due to localized overheating.

[0088] Through the above technical solution, this application effectively solves the problems of weak output signal and poor anti-interference ability of heat flux sensors in high-temperature environments. The increase in the number of nodes enables the sensor to maintain a stable thermoelectric potential output in environments above 1500℃, meeting the high-precision real-time monitoring requirements of heat flux density in scenarios such as hypersonic vehicle thermal protection systems.

[0089] This application further proposes the following preparation steps: mixing chromium-doped indium oxide powder and undoped indium oxide powder with glass powder and ethyl fiber respectively to prepare a printing paste; sequentially depositing chromium-doped indium oxide thermocouple arms and undoped indium oxide thermocouple arms on a high-temperature resistant ceramic substrate using a screen printing process; subjecting the printed substrate to a first high-temperature sintering treatment in air; sequentially depositing a thermal resistance layer on the high-temperature resistant ceramic substrate using a screen printing process; and subjecting the substrate with the printed thermal resistance layer to a second high-temperature sintering treatment in air.

[0090] Among them, chromium-doped indium oxide powder refers to indium oxide-based powder materials modified with chromium. Specifically, it can be prepared by solid-state synthesis, mixing chromium oxide and indium oxide in a predetermined ratio and calcining them to form thermocouple arms with different Seebeck coefficients. Sintering aids such as glass powder are inorganic additives that promote material densification. Specifically, borosilicate-based low-melting-point glass powder can be used to achieve interfacial bonding between the thermoelectric material and the substrate by lowering the sintering temperature. Thickeners such as ethyl cellulose are organic binders that adjust the rheological properties of the slurry. Specifically, a mixed solution of ethyl cellulose and terpineol can be used to ensure the dimensional accuracy of the printed pattern. Two high-temperature sintering processes refer to controlling the sintering temperature profile in stages. The first sintering is used for grain growth of the thermoelectric material, and the second sintering is used for interfacial strengthening between the thermal resistance layer and the substrate.

[0091] Specifically, by preparing printable pastes of chromium-doped and undoped indium oxide separately, thermocouple arrays are alternately deposited on a substrate using screen printing. A first high-temperature sintering process creates a dense microstructure in the thermoelectric material, while melting glass powder promotes chemical bonding between the material and the substrate. The subsequently deposited alumina-based thermal resistance layer forms a continuous insulating layer through a second sintering process. The temperature profiles of the two sintering processes can be independently optimized; for example, the first sintering temperature can be slightly higher than the second to prioritize the crystallinity quality of the thermoelectric material. This step-by-step sintering strategy avoids interfacial reactions common in co-firing of multilayer structures while ensuring the structural integrity of each functional layer.

[0092] Compared to existing technologies, traditional heat flux sensor fabrication often employs a single co-firing process, leading to interfacial cracks due to differences in the thermal expansion coefficients of different material layers. This approach utilizes stepwise deposition and staged sintering to ensure stable structures for both the thermoelectric material layer and the thermal resistance layer. For example, after the first sintering, the printing and sintering of the thermal resistance layer avoids thermal shock to the already formed thermocouple arm. Furthermore, the amount of glass powder added can be adjusted according to the required slurry viscosity. For instance, adding 5%–15% glass powder to the indium oxide slurry ensures sintering activity without affecting the resolution of the screen-printed pattern.

[0093] Through the above technical solution, this application effectively solves the interface mismatch problem of multilayer thin film structures during high-temperature co-firing, ensuring the coordinated operation of the thermocouple arm and the thermal resistance layer at extreme temperatures. The stepwise sintering process reduces the accumulation of interlayer thermal stress, and the addition of glass powder enhances the bonding strength between the material and the substrate. The thermopile structure prepared in this way can still maintain stable Seebeck output characteristics at a high temperature of 1500℃.

[0094] This application further proposes that the sintering temperature for both the first and second high-temperature sintering treatments is 1450~1550℃, and the holding time is 0.5~2 hours.

[0095] High-temperature sintering refers to the process of forming a dense structure in materials through high-temperature heat treatment. This can be achieved using a box-type resistance furnace or a tube sintering furnace. The selection of the sintering temperature range must balance material densification and grain growth. Holding time refers to the length of time the material is held at a set temperature. This can be precisely adjusted using a programmed temperature control system. Too short a holding time may lead to insufficient sintering, while too long a time may cause abnormal grain growth.

[0096] Specifically, in the fabrication of a chromium-doped indium oxide high-temperature heat flux sensor, the substrate after printing the paste is placed in a high-temperature sintering furnace, and the temperature is increased to the target range in a stepped manner. For example, during the first sintering, the temperature can be controlled at 1450℃ and held for 0.5 hours to allow the thermocouple arm material to fully crystallize and form a stable bond with the substrate; during the second sintering, the temperature can be increased to 1550℃ and held for 0.5 hours to ensure that the thermal resistance layer material achieves high density. By coordinating the temperature and time control of the two sintering processes, the thermal expansion matching between the thermoelectric material and the substrate can be optimized while avoiding phase transitions or decomposition of the material at high temperatures.

[0097] Compared to existing technologies, conventional sintering processes mostly employ single-stage sintering. The significance of staged sintering lies in balancing the high-temperature performance of the material with structural integrity: through two sintering steps, it ensures that the thermoelectric material (chromium-doped / undoped indium oxide) is fully cured and its electrical properties are stabilized at the first high temperature, avoiding secondary thermal damage; it also allows the thermal resistance layer to independently optimize its density in subsequent sintering, while preventing cracking and delamination caused by differences in shrinkage rates or interfacial reactions between different material layers, ultimately ensuring the reliability and measurement accuracy of the sensor in extreme environments.

[0098] Through the above technical solution, this application solves the problem that traditional sintering processes cannot simultaneously achieve material density and structural stability, enabling the prepared thermopile to still have low contact resistance and high mechanical strength in high-temperature environments above 1500℃, thereby significantly improving the sensor's thermal shock resistance and long-term operational reliability.

[0099] This application further proposes a thin-film thermopile comprising a first thin-film layer with a thickness of 10 μm to 50 μm, and a second and third thin-film layers with a thickness of 5 μm to 30 μm.

[0100] The first thin film layer refers to a high-temperature resistant insulating material layer such as alumina, which serves as a thermal resistance layer. The thickness can be controlled by adjusting the viscosity of the screen printing paste and the number of printing cycles. This thickness range can ensure thermal resistance performance while avoiding a decrease in heat conduction efficiency due to excessive thickness.

[0101] The second and third thin film layers refer to thermocouple arms composed of chromium-doped indium oxide and undoped indium oxide. The thickness can be adjusted by controlling the amount of slurry deposition and the sintering shrinkage rate. This thickness range meets the carrier transport requirements of thermoelectric materials at high temperatures and avoids insufficient mechanical strength caused by excessive thinness.

[0102] Specifically, the thickness of the first thin film layer is limited to 10 μm to 50 μm, for example, by multiple screen printing layers to form a uniform and dense structure, thereby effectively blocking heat flow transfer and reducing substrate thermal stress in high-temperature environments. The thicknesses of the second and third thin film layers are controlled within the range of 5 μm to 30 μm, for example, through single-pass printing or gradient sintering processes, ensuring that the thermocouple arm has sufficient carrier migration paths at high temperatures, while also matching the thermal expansion coefficient with the thermal resistance layer. The synergistic design of the thickness ranges of each layer enables the thermopile to maintain stable thermoelectric output even at extreme temperatures. Compared to existing technologies, the thermal resistance layer thickness of traditional thermopile is typically over 100 μm, leading to sluggish thermal response and susceptibility to thermal stress cracking. In contrast, the thermocouple arm thickness is generally less than 5 μm, making it prone to fracture or performance degradation at high temperatures. This application optimizes the thickness range of each layer, thereby improving both the thermal conductivity of the thermal resistance layer and the mechanical stability of the thermoelectric material.

[0103] Through the above technical solution, this application solves the problem of interface peeling between the thermal resistance layer and the thermoelectric material due to thickness mismatch under high temperature environment, and avoids the interruption of the charge carrier transport path caused by the thermocouple arm being too thin, thereby significantly improving the long-term working reliability of the sensor under extreme conditions above 1500℃.

[0104] This application further proposes connecting high-temperature stable electrodes to the sintered thermopile structure and performing high-temperature resistant encapsulation.

[0105] Among them, high-temperature stable electrodes refer to metal conductors that can maintain conductivity and interface stability in high-temperature environments. Specifically, they can be made of platinum, nickel-chromium alloys or nickel-silicon alloys. These materials have high melting points and low oxidation rates, which can maintain stable electrical signal transmission in high-temperature heat flow measurements.

[0106] High-temperature resistant packaging refers to the shell packaging process that provides hermetical protection for the thermopile structure. Specifically, alumina ceramic or high-temperature alloy materials can be used as the packaging shell, and the seal can be achieved by laser welding or high-temperature adhesives. The packaging structure needs to match the thermal expansion coefficient of the thermopile to reduce thermal stress.

[0107] Specifically, after the thermopile is sintered, a high-temperature stable electrode is fabricated at the end of the thermocouple arm using screen printing or sputtering, forming a metallurgical interface between the electrode material and the thermocouple arm. During encapsulation, the thermopile structure is placed within a pre-formed ceramic shell, and a high-temperature brazing process is used to achieve a sealed connection between the shell and the substrate. The encapsulation can be filled with an inert gas to suppress high-temperature oxidation. This process solves the technical problems of electrode interface failure and encapsulation cracking under high-temperature conditions by optimizing the matching between the electrode material and the encapsulation structure.

[0108] In some specific embodiments, the thickness of the high-temperature stable electrode can be controlled within the range of 1 to 5 micrometers, for example, by depositing a platinum layer using a magnetron sputtering process; the packaging shell can be made of yttrium oxide-stabilized zirconia ceramic, for example, by achieving seamless bonding between the shell and the substrate through a hot isostatic pressing process.

[0109] Compared to existing technologies, traditional heat flow sensors typically use silver paste or copper-based materials for their electrodes, which are prone to oxidation and detachment at temperatures above 800°C. Their encapsulations often use silicone or ordinary glass, which softens and cracks at high temperatures. This solution introduces platinum-based high-temperature alloy electrodes and a ceramic-metal composite encapsulation, enabling the sensor to maintain electrode conductivity stability and encapsulation structural integrity in environments above 1500°C.

[0110] Through the above technical solution, this application achieves reliable electrical contact of thermopile electrodes at extreme temperatures, and effectively isolates the external oxidation environment through hermetic encapsulation, enabling the sensor to have long-term working stability in high-temperature heat flow measurement, and solving the measurement signal drift problem caused by electrode interface degradation and encapsulation failure in the prior art.

[0111] This application further proposes connecting a high-temperature stable electrode to the sintered thermopile structure and encapsulating it with high-temperature resistance. The high-temperature stable electrode is made of high-temperature resistant electrode materials such as platinum, nickel-chromium, and nickel-silicon.

[0112] High-temperature stable electrodes refer to electrode materials that maintain physicochemical stability and conductivity under high-temperature environments. Specifically, they can be made from platinum, nickel-chromium alloys, or nickel-silicon alloys. Platinum has a high melting point and oxidation resistance, nickel-chromium alloys have high-temperature oxidation resistance and thermal shock resistance, and nickel-silicon alloys can form a stable silicide protective layer at high temperatures. These materials can effectively maintain the interfacial contact stability between the electrode and the thermoelectric material in high-temperature environments, avoiding signal drift or failure caused by electrode oxidation or thermal expansion mismatch.

[0113] Specifically, in the thermopile fabrication process, platinum, nickel-chromium, or nickel-silicon materials are used to form electrode structures through sputtering, evaporation, or screen printing, followed by high-temperature encapsulation. A stable ohmic contact is formed between the electrode materials and the chromium-doped indium oxide thermoelectric layer through matched thermal expansion coefficients and interfacial diffusion control. During high-temperature heat flow measurement, the electrode materials' inherent oxidation resistance suppresses the formation of the interfacial oxide layer, ensuring efficient transmission of the thermoelectric signal.

[0114] Compared to existing technologies, traditional heat flow sensors often use conventional metals such as silver and copper as electrode materials, which are prone to oxidation, creep, or interface peeling at high temperatures, leading to increased contact resistance or even open circuits. In contrast, materials such as platinum, nickel-chromium, and nickel-silicon significantly extend the lifespan of electrodes under extreme temperature conditions by optimizing high-temperature stability and interfacial bonding strength.

[0115] Through the above technical solution, this application solves the technical problem of interface failure between electrode material and thermoelectric layer under high temperature environment, ensures the signal stability and measurement accuracy of sensor when working for a long time above 1500℃, and provides key support for reliable detection of ultra-high temperature heat flux density.

[0116] Table 1

[0117] Please see Figure 3 As shown in Table 1, a high-temperature heat flux sensor based on chromium-doped indium oxide was calibrated using a radiation method. Sensor calibration was achieved by precisely controlling the heat flux density. First, the sensor to be calibrated was mounted on an adjustable sample stage, maintaining a fixed distance from the standard radiation source. The power of the radiation source was adjusted to achieve the preset heat flux value, while the actual heat flux density was monitored using a standard heat flux meter. The correspondence between the sensor's output signal and the standard value was recorded, and repeated measurements at different power levels were used to establish the input-output characteristic curve.

[0118] When the heat flow is 34.2 kW / m 2 Increased to 196.7kW / m 2 At that time, the output of the sensor increased from 0.33mV to over 1.77mV. The sensor exhibits significant sensitivity to heat flow. After five calibrations, the average sensitivity of the sensor is 9.4μV (kW / m). 2 It exhibits high linearity in high-temperature heat flow measurements, with a linear fitting R0. 2 It is 0.9993 Please refer to Figure 4 To determine the dynamic response characteristics of the heat flux sensor, a pulsed laser method was employed. A high-power laser was selected as the transient heat source, and the laser output power and beam diameter were precisely adjusted to ensure uniform irradiation of the sensor's effective area. During the experiment, a pulsed laser command (5Hz, 50% duty cycle, duration 1000ms) was issued through the laser control unit, simultaneously triggering a high-speed data acquisition device (sampling rate 250kHz / s) to fully record the time-domain variation of the sensor's output signal. By analyzing the acquired transient response waveform, the duration of the signal rise phase (from baseline to 63.2% of the steady-state value) or fall phase (decay from the steady-state value to 10%) was extracted as the response time parameter. Testing and analysis showed that the heat flux sensor exhibits a fast dynamic response capability of 16ms.

[0119] In summary, this invention discloses a high-temperature heat flow sensor based on chromium-doped indium oxide and its fabrication method. By precisely controlling the doping ratio and spatial distribution of chromium in the indium oxide crystal, acceptor levels and localized electronic states are constructed within the material, thereby optimizing carrier concentration and migration characteristics, altering the Seebeck coefficient, and maintaining its structural stability under high-temperature conditions. When combined with pure indium oxide to form a thermocouple pair, this combination exhibits excellent thermoelectric conversion efficiency, making it particularly suitable for heat flow detection under ultra-high temperature conditions. In terms of fabrication, screen printing technology is employed, and a high-precision thermopile array is constructed on a special high-temperature ceramic substrate by optimizing the paste composition and printing parameters. A stepwise sintering process ensures that both the thermoelectric functional layer and the thermal resistance layer achieve ideal densification and interfacial bonding strength. The resulting sensor product exhibits excellent high-temperature oxidation resistance and long-term operational reliability, and its output signal demonstrates excellent repeatability and stability.

[0120] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A high temperature heat flux sensor based on chromium doped indium oxide, characterized in that, The application relates to a high-temperature heat flow sensor based on chromium-doped indium oxide, which comprises a body (1), a second thin film layer (3) and a third thin film layer (4) arranged on the body (1), the leading ends of the second thin film layer (3) and the third thin film layer (4) form a thermocouple pair, and the thermocouple pair is arrayed to form a thermopile, a first thin film layer (2) is arranged on the thermopile, the third thin film layer (3) is a chromium-doped indium oxide thin film or an indium oxide thin film, and the third thin film layer (4) is an indium oxide thin film or a chromium-doped indium oxide thin film matched with the third thin film layer (3).

2. The high temperature heat flux sensor based on chromium doped indium oxide according to claim 1, characterized in that The doping concentration of chromium in the chromium-doped indium oxide is that the mass ratio of chromium oxide to indium oxide is 1:1 to 10:

1.

3. The high temperature heat flux sensor based on chromium doped indium oxide according to claim 1, characterized in that The thickness of the first thin film layer (2) is 10-50 mu m.

4. The high temperature heat flux sensor based on chromium doped indium oxide according to claim 3, characterized in that The first thin film layer (2) is a high-temperature-resistant insulating material.

5. The high temperature heat flux sensor based on chromium doped indium oxide according to claim 1, characterized in that, The thickness of the second thin film layer (3) and the third thin film layer (4) is 5-30 mu m.

6. The high temperature heat flux sensor based on chromium doped indium oxide according to claim 1, characterized in that The number of nodes formed by the second thin film layer (3) and the third thin film layer (4) is greater than or equal to 10, and the spacing between the nodes is 0.5-1 mm.

7. A method of making a high temperature thermal flow sensor based on chromium doped indium oxide as claimed in claim 1, characterized in that, The application further discloses a preparation method of the high-temperature heat flow sensor based on chromium-doped indium oxide, which comprises the following steps: The chromium-doped indium oxide powder and the undoped indium oxide powder are mixed with sintering aids and thickening agents respectively to prepare printing slurry; The printing slurry is used to sequentially deposit the chromium-doped indium oxide thermocouple arm and the undoped indium oxide thermocouple arm on the body by a screen printing process; The printed body is subjected to first high-temperature sintering treatment in air, and then a heat resistance layer is sequentially deposited by a screen printing process; The body with the printed heat resistance layer is subjected to second high-temperature sintering treatment, a high-temperature stable electrode is connected to the sintered thermopile structure, and high-temperature-resistant packaging is carried out, so that the high-temperature heat flow sensor based on chromium-doped indium oxide is obtained.

8. The method of claim 7, wherein the chromium-doped indium oxide based high temperature heat flux sensor is prepared by the steps of: The sintering temperature of the first high-temperature sintering treatment and the second high-temperature sintering treatment is 1450-1550 DEG C, and the holding time is 0.5-2 hours.

9. The method of claim 7, wherein the chromium-doped indium oxide based high temperature heat flux sensor is prepared by the steps of: The high-temperature stable electrode is selected from platinum, nickel-chromium and nickel-silicon.

10. Application of the high-temperature heat flow sensor based on chromium-doped indium oxide in super-high-temperature heat flow measurement according to claim 1.

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