Thin Film Thermocouples Research Articles

Measurement and Analysis of Surface Temperature Gradients on Magnetron Sputtered Thin Film Growth Studied Using NiCr/NiSi Thin Film Thermocouples.

In the general analysis of thin-film growth processes, it is often assumed that the temperature of the film growth surface is the same as the temperature of the film growth substrate. However, a temperature gradient exists between the film growth surface and film growth substrate. Using the growth surface of TiO2 thin films as an example, the temperature gradient of the film growth surface is tested and analyzed. A NiCr/NiSi thin-film thermocouple is fabricated using the direct-current pulse magnetron sputtering method. A three-layer NiCr/NiSi thin-film thermocouple temperature measurement system is established to measure the temperature gradient of the film growth surface. The growth surface temperature and substrate temperature of the TiO2 thin films are measured. For a sputtering power density of 0.83W cm- 2, the temperature difference between the first and second layers is 104.79°C, while the temperature difference between the second and third layers is 39.92°C. A standard K-type thermocouple is used to measure the substrate temperature, which is recorded to be 132.05°C, consistent with common measurements of substrate temperature. The heat conduction on the film growth surface in the vacuum chamber is examined and a model for the temperature measurement device during film growth is constructed.

Sandwich probe temperature sensor based on In2O3-IZO thin film for ultra-high temperatures

High-temperature thin-film thermocouples (TFTCs) have attracted significant attention in the aerospace and steel metallurgy industry. However, previous studies on TFTCs have primarily focused on the two-dimensional planar-type, whose thermal sensitive area has to be perpendicular to the test environment, and therefore affects the thermal fluids pattern or loses accuracy. In order to address this problem, recent studies have developed three-dimensional probe-type TFTCs, which can be set parallel to the test environment. Nevertheless, the probe-type TFTCs are limited by their measurement threshold and poor stability at high temperatures. To address these issues, in this study, we propose a novel probe-type TFTC with a sandwich structure. The sensitive layer is compounded with indium oxide doped zinc oxide and fabricated using screen-printing technology. With the protection of sandwich structure on electrode film, the sensor demonstrates robust high-temperature stability, enabling continuous working at 1200 °C above 5 h with a low drift rate of 2.3 °C·h−1. This sensor exhibits a high repeatability of 99.3% when measuring a wide range of temperatures, which is beyond the most existing probe-type TFTCs reported in the literature. With its excellent high-temperature performance, this temperature sensor holds immense potentials for enhancing equipment safety in the aerospace engineering and ensuring product quality in the steel metallurgy industry.

Utilizing screen printing technology to fabricate tungsten-rhenium thick film thermocouples with a maximum temperature limit of 1600 °C

Tungsten-rhenium thick film thermocouples (TFTCs) show excellent potential for in-situ high-temperature monitoring due to their high-temperature resistance. However, the only reported method for preparing tungsten-rhenium thin film thermocouples is magnetron sputtering. The upper limit of temperature resistance of thetungsten-rhenium thin film thermocouples prepared by this method is low because the thickness is reduced by continuous thermal ablation at high temperatures. In this work, screen printing technology is used to prepare tungsten-rhenium TFTCs. The tungsten-rhenium TFTCs’ temperature accuracy is better than ±1.5 %, repeatability is better than 0.9 %, and drift is only 0.26 %/h at 1600 °C. Finally, the tungsten-rhenium TFTC temperature ring array is installed in a tubular furnace for high-temperature monitoring, and the tungsten-rhenium TFTC is heated in the air using a high-temperature flame gun at approximately 1000 °C for up to 30 s. This method to fabricate tungsten-rhenium TFTCs has the potential for temperature measurement in extremely harsh environments.

Design and fabrication of metal spherical conformal thin film multisensor for high-temperature environment

Conformal thin-film sensors enable precise monitoring of the operating conditions of components in extreme environments. However, the development of these sensors encounters major challenges, especially in uniformly applying multiple film layers on complex metallic surfaces and accurately capturing diverse operational parameters. This work reports a multi-sensor design and multi-layer additive manufacturing process targeting spherical metallic substrates. The proposed high-temperature dip-coating and self-leveling fabrication process achieves high-temperature thin-film coatings with excellent uniformity, high-temperature electrical insulation, and adhesion properties. The fabricated Ag/Pt thin film thermocouple arrays and a heat flux sensor exhibit a maximum temperature resistance of up to 960 °C, with thermoelectric potential outputs and high-temperature resistance closely mirroring those of wire-based Ag/Pt thermocouples. Harsh environmental testing was conducted using high-power lasers and a flame gun. The results show that the array of thin-film conformal thermocouples more accurately reflected temperature changes at different points on a spherical surface. The heat flux sensors achieve responses within 95 ms and withstand environments with heat fluxes over 1.2 MW/m2. The proposed multi-sensor design and fabrication method offers promising monitoring applications in harsh environments, including aerospace and nuclear power.

High-temperature protection performance of Mg-doped Al2O3 protective layers on the thin film thermocouples

Mg-doped Al2O3 protective layers were deposited on Pt–PtRh10 (S-type) thin film thermocouples (TFTCs) by reactive magnetron sputtering. The changes in the composition, microstructure, and element distribution of the Mg-doped Al2O3 films before and after annealing at 1200 °C for 3 h were investigated using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDS). The results indicate that incorporating MgO into Al2O3 as an enhancement phase not only inhibits the crystallization and phase transformation of Al2O3 but also promotes the formation of MgAl2O4, sequentially further enhancing the material's high-temperature protective properties. The thermoelectric properties of S-type TFTCs with 1.6 μm thick Al2O3 and Mg-doped Al2O3 protective layers were explored, respectively. The results of static calibration at high temperatures demonstrate that the TFTCs with the Mg-doped Al2O3 protective layer can operate at 1148 °C for over 96 h and at 1480 °C for a brief period. Following 4 calibration cycles, compared to the TFTCs with the Al2O3 protective layer, the average Seebeck coefficients of the TFTCs with the Mg-doped Al2O3 protective layer exhibit a slower decline rate, and its drift rate during the 4th cycle is merely 3.28 °C/h. The TFTCs featuring Mg-doped Al2O3 protective layers demonstrate extended lifetimes, superior high-temperature stability, and enhanced reliability when contrasted with those utilizing undoped Al2O3 protective layers. These attributes offer valuable insights into the progression of TFTC technology.

Research on the improvement of the adhesion strength of the Cu films deposited on the Al2O3 films

Due to the significant discrepancy in the coefficient of linear thermal expansion between Cu and ceramic in T-type thin film thermocouples, the Cu thin films often exhibit a low adhesion strength with the ceramic layers (Al2O3). In order to improve the adhesion strength of the Cu with the Al2O3 films, several methods during preparation were studied. First, different thicknesses of the Cu thin films deposited at different deposition temperatures on the Al2O3 thin films prepared by the magnetron sputtering were studied. Second, the Ti/Ni buffer layer between the Cu and the Al2O3 thin films was prepared. Finally, the average roughness of Al2O3 was studied. The adhesion strength of the Cu with the Al2O3 thin films, the microstructure of the surface and the cross section of the Cu and the Al2O3 thin films, and the grain size and the roughness of the films are characterized by nanoscratch testing, scanning electron microscopy, and atomic force microscopy. The adhesion strength of the Cu films with the Al2O3 films increases with an increase in the thickness of the Cu thin films and the roughness of the Al2O3 thin films and the addition of the Ti/Ni buffer layers.

Nanosecond-level second-order characteristics in dynamic calibration of thin film thermocouples by short-pulse laser

In this study, we explore the dynamic response of thin-film thermocouples (TFTCs) to transient temperature changes, emphasizing their nanosecond response capabilities. Traditionally, TFTCs are modeled as first-order systems. By employing magnetron sputtering, we have prepared NiCr/NiSi TFTCs with a novel integrated lead method. A 7.6 ns short-pulse laser served as the heat source, capturing the TFTCs’ transient response with a high-speed collector at 200 M/s. Unexpectedly, the TFTCs’ response curves exhibited oscillations at high acquisition rates. Through frequency response analysis, we have established a pulse response model for the TFTCs that is highly consistent with experimental results. For the first time, we confirmed the TFTCs’ second-order dynamic characteristics. Furthermore, our findings that various substrate materials and lead methods impact the damping characteristics of TFTCs led us to conduct pulsed laser damage experiments. These experiments revealed a correlation between damping properties and the extent of damage.

Research on a dedicated thin-film thermocouple testing system for transient temperature measurement

The thin-film thermocouple (TFTC) is featured on small heat capacity and rapid response speed for transient temperature measurements under narrow space and difficult installation. Consequently, we propose a novel transient temperature testing system specifically designed for TFTC. This system features signal conditioning circuits with extended bandwidth and superior transfer speeds, a cold junction compensation method that supports customizable indexing tables, and an adaptive data filtering approach that precisely balances the smoothing of steady-state data with rapid responsiveness to transient data. This approach effectively mitigating the measurement distortion of transient temperature signals and the nonlinear phenomenon in cold junction compensation for TFTC. Utilizing NiCr/NiSi TFTC, we evaluated the system’s accuracy, demonstrating a precision range of −0.5 °C–0.25 °C within 20 °C–100 °C, and a response delay under 0.1 ms. Compared to traditional thermocouple measurement systems, our system exhibits a finer time-domain resolution. Lastly, we successfully applied this system to observe the response of TFTC under the thermal load of short-pulse laser shocks, measuring a time constant of only 1.16 ms for the TFTC. This novel transient temperature testing system provides a new approach for TFTC to achieve online dynamic measurement and online calibration, and provides technical support for TFTC measurement technology towards engineering applications.

Oxidation behaviour of NiSi–NiCr thin film thermocouples and antioxidation effect of SiNxOy film

NiSi–NiCr thin film thermocouples (TFTCs) have significant application value as contact temperature sensors in cutting temperature measurements owing to their fast response and negligible volume. However, due to the relatively high chemical activity of Ni-based alloys, high-temperature oxidation strongly affects the operational reliability of NiSi–NiCr TFTCs. In this respect, depositing an anti-oxidation coating onto the surface of NiSi–NiCr TFTCs is considered an effective way to protect them in high-temperature environments. In this study, NiSi and NiCr films were deposited on cemented carbides and annealed at 200 °C–600 °C in air. Scanning electron microscope, X-ray diffraction spectroscopy, X-ray photoelectron spectroscopy, and four-probe resistivity tests were used to characterize the microstructure and resistivity of NiSi and NiCr film. Then SiNxOy films were deposited onto the NiSi and NiCr films and compared with uncoated samples after annealing at 600 °C. The effect of SiNxOy films on the thermal stability and thermoelectric output of NiSi–NiCr TFTCs was investigated. The results show that the NiSi film was partially oxidized at 200 °C and entirely oxidized when the temperature exceeded 400 °C. The completely oxidized NiSi films had evident defects and cracks, and the resistivity increased by a factor of over 1000. The NiCr film could not be completely oxidized at 600 °C, which is attributed to the formation of Cr2O3 as an external oxide barrier layer. Below 600 °C, SiNxOy films could effectively protect NiSi and NiCr films from oxidation. Thus, the addition of SiNxOy film increases the maximum temperature at which NiSi–NiCr TFTCs can be used.

Study on aluminium oxide doping modification of indium oxide and thermoelectric properties

Traditional thermocouples face challenges in meeting the temperature measurement requirements of crucial aero-engine components, such as low interference, high temperature resistance, quick response, and in-situ measurement. The temperature measurement requirements mentioned above can be satisfied by thin film thermocouples, thanks to advancements in thin-film preparation technology. In this study, the indium oxide (In2O3) was calculated using first principle calculation both before and after doping. It was found that doping Aluminium oxide (Al2O3) can increase the Seebeck coefficient of In2O3. Solid-phase sintering was used to create aluminum oxide-doped In2O3 nanopowders, and thin film thermocouples were fabricated using screen printing. The thermoelectric characteristics of thin film thermocouples were studied to analyze the effects of different annealing procedures and doping concentrations. The optimal annealing process was determined to be at 1300 °C for 1 h, and the ideal doping ratio was found to be Al0.1In2O3.15. The indium oxide film doped with aluminum oxide exhibits a Seebeck coefficient that is 45.9% higher than that of the undoped indium oxide film. The thin film thermocouples underwent tests for impact and vibration resistance, laser pulse response, surface and cross-section morphology, X-ray diffraction, and thermoelectric output. It has been confirmed that doping indium oxide with aluminum oxide can increase a material's Seebeck coefficient. Additionally, a thin-film temperature sensor that has been prepared can be used in challenging conditions to meet the temperature measurement requirements of an aero engine.

Mechanism of Seebeck coefficient variation at the output of NiCr/NiSi thin film thermocouple with different wires

In this paper, by using magnetron sputtering to prepare NiCr/NiSi thin film thermocouples, the static calibration method is used for NiCr/NiSi thermocouples with rapid temperature calibration experiments. Different temperature calibration curves are obtained. The Seebeck coefficient of NiCr/NiSi thin film thermocouples connected to NiCr/NiSi wires is significantly higher (41.39 μV/°C) than that of NiCr/NiSi wires (0 μV/°C). The Seebeck coefficient (41.39 μV/°C) of the NiCr/NiSi thin-film thermocouple connected to copper wire is significantly higher than that of the thermocouple connected to copper wire (0 μV/°C). The problem of the Seebeck coefficient of the K-type thermocouple is analyzed by experimental data, which provides the relevant parameter basis for the use of the K-type thermocouple. The method has the advantages of simple equipment, convenient operation, accurate and reliable data, and provides a basis for the sensor to measure the temperature measurement.

Analysis of the Effect of Copper Doping on the Optoelectronic Properties of Indium Oxide Thin Films and the Thermoelectric Properties of an In2O3/Pt Thermocouple

The detection and real-time monitoring of temperature parameters are important, and indium oxide-based thin film thermocouples can be integrated on the surface of heaters because they operate normally under harsh conditions and provide accurate online temperature monitoring. The higher stability and appropriate optical and electrical properties of In2O3 make it very suitable as an electrode material for thermocouple sensors. This work demonstrates that copper doping can alter the optical and electrical properties of In2O3 films and regulate the output performance of thermocouples. Copper-doped In2O3 thin films were prepared using the magnetron co-sputtering method. The doping concentration of Cu was controlled using direct current (DC) power. An In2O3/Pt thermocouple sensor was prepared, and the optoelectronic and thermocouple properties were adjusted by changing the copper doping content. The thickness valve of the thin film sample was 300 nm. The results of the X-ray diffraction suggested that the structure of the doped In2O3 thin films was cubic. The results of the energy-dispersive X-ray analysis revealed that Cu was doped into the In2O3 thin films. All deposited films were n-type semiconductor materials according to Hall effect testing. The 4.09 at% Cu-doped thin films possessed the highest resistivity (30.2 × 10−3 Ω·cm), a larger carrier concentration (3.72 × 1020 cm−3), and the lowest carrier mobility (0.56 cm2V−1s−1). The optical band gap decreased from 3.76 to 2.71 eV with an increase in the doping concentration, and the transmittance of the film significantly reduced. When the DC power was increased, the variation range of Seebeck coefficient for the In2O3/Pt thermocouple was 152.1–170.5 μV/°C, and the range of thermal output value was 91.4–102.4 mV.

Integrated design and fabricate of high sensitivity built-in thin-film thermocouple temperature measurement tool

Abstract Cutting temperature is playing a key role in evaluating the cutting process, which significantly affects the tool wear and the quality of the workpiece. Aiming at the problems of low precision, low aging, and poor stability of cutting temperature measurement on the front tool face, an integrated design and production scheme of a high sensitivity built-in wireless temperature measurement tool was proposed. The temperature distribution position on the front tool face was analyzed with 3D finite element simulation software, and the thermal contact position of the main and secondary film thermocouples was determined. SiO2 insulated films and NiCr/NiSi film thermocouples were prepared on the front tool surface by femtosecond laser micromachining, electrolyte-plasma polishing, plasma enhanced chemical vapor deposition and magnetron sputtering, and a static calibration experiment system for sensitivity and accuracy of the temperature measuring tool for the film thermocouple was established, and Seebeck coefficient of the film thermocouple was obtained. According to the actual cutting conditions, the wireless temperature measuring system of the thin film thermocouple tool was built and the field cutting test was carried out to obtain the influence law of different cutting parameters on the cutting temperature, and further verify the feasibility of the thin film temperature measuring sensor. The research results show that: Seebeck coefficients of the two kinds of thermocouples prepared by the NiCr/NiSi thin film thermocouple temperature measuring tool are 34.97 μV/°C and 34.96 μV/°C, and the slope of the temperature data fitting curve is 1.00398 and 0.997475, respectively. The linear correlation coefficient R2 is close to 1, which is close to the standard K-type thermocouple, which shows good sensitivity and accuracy. At the same time, the temperature measurement results are close to the commercial standard K thermocouple, and the error is less than 5%, indicating that the developed film thermocouple has a high measurement accuracy and can meet the needs of temperature measurement. Actual cutting test is carried out with developed wireless temperature measuring device of thin film thermocouple, which shows this device can meet the requirements of tool temperature measurement, and the feasibility of thin film temperature measuring sensor is further verified. The research provide technical reference for industrial intelligent manufacturing in order to realize the wireless measurement of cutting area temperature of tool front.

Preliminary Investigation of Thermoelectric Electromotive Force Oscillation of NiCr/NiSi Thin Film Thermocouple in Dynamic Calibration.

In order to reveal the dynamic response characteristic of thin film thermocouples (TFTCs), the nichrome/nisil (NiCr/NiSi) TFTCs are prepared onto the glass substrate. With short pulse infrared laser system, NiCr/NiSi TFTCs are dynamically calibrated. The thermoelectric electromotive force (TEF) curves of NiCr/NiSi TFTCs are recorded by the memory hicorder system, which could reflect TEF signals with resolution ratio in nanosecond and microvolt, simultaneously. With increasing laser energy from 15.49 to 29.59 mJ, TEF curves display more and more violent oscillation, even negative value. The results show that the bounce of thermal energy happens between two interfaces of TFTCs because the thermal conductivity of glass and air is significantly lower than that of NiSi/NiCr TFTCs. The bounce of thermal energy results in the obvious decrease of nNiCr and nNiSi, as well as oscillation of TEF. For laser energy in 29.59 mJ, the bounce of thermal energy in NiCr film could result in nNiCr < nNiSi. Then, TEF value appears abnormal negative value. Based on the results, the complex thermal energy transport process in TFTCs dynamic calibration is revealed, which results in the oscillation of thermal energy and TEF signal.

Inclined ITO thin film with thermoelectric anisotropy: A promising sensitivity material for ultraviolet pulsed photodetector based on light-induced transverse voltage effect

Indium tin oxide (ITO) thin film, a typical transparent conductive oxide, is usually used as a material for thin film thermocouples due to its large Seebeck coefficient and low resistivity. In this work, inclined epitaxial ITO thin films have been prepared on c-axis miscut YSZ (001) single crystal substrates. The distinct response voltages, oriented perpendicular to the temperature gradient, are detected based on the light-induced transverse voltage (LITV) effect, originating from the anisotropic Seebeck coefficient ΔS between the ab-plane and c-axis of ITO thin films. Following the high-temperature annealing process, ITO thin films experience a significant increase in ΔS by an order of magnitude, thereby amplifying the response voltage. The voltage amplitudes have a good linear relationship with the inclined angles (sin2α). Moreover, under the irradiation of a 248 nm pulsed laser, the response voltage exhibited a fast response time with a rise time τr of 20∼26 ns and decay time τd of 18∼24 ns due to the intrinsic characteristic of low resistivity, demonstrating its potential to be a candidate material for fast response self-powered ultraviolet photodetector.

High-Temperature Failure Evolution Analysis of K-Type Film Thermocouples.

Ni90%Cr10% and Ni97%Si3% thin-film thermocouples (TFTCs) were fabricated on a silicon substrate using magnetron sputtering technology. Static calibration yielded a Seebeck coefficient of 23.00 μV/°C. During staged temperature elevation of the TFTCs while continuously monitoring their thermoelectric output, a rapid decline in thermoelectric potential was observed upon the hot junction reaching 600 °C; the device had failed. Through three cycles of repetitive static calibration tests ranging from room temperature to 500 °C, it was observed that the thermoelectric performance of the TFTCs deteriorated as the testing progressed. Utilizing the same methodology, Ni-Cr and Ni-Si thin films corresponding to the positive and negative electrodes of the TFTCs were prepared. Their resistivity after undergoing various temperature annealing treatments was measured. Additionally, their surfaces were characterized using Scanning Electron Microscopy (SEM) and X-ray Photoelectron Spectroscopy (XPS). The causes behind the decline in thermoelectric performance at elevated temperatures were analyzed from both chemical composition and microstructural perspectives.

Polymer-derived ceramic thin-film thermocouples for high temperature measurements

Thin-film thermocouples are used as temperature detection components in aircraft engines. However, the preparation of traditional thin-film thermocouples is complex, and their high-temperature stability performance attributes are poor. In this study, polymer-derived ceramic (PDC) technology is introduced to prepare polymer-derived ceramic thin-film thermocouples. Due to the superior high-temperature and adhesion performance characteristics of polymer-derived ceramics and the protective effects of the products of polymer precursors on the thin films, the performance attributes of thin-film thermocouples are greatly improved. After simplifying the preparation process and outputting a large thermoelectric potential, the polymer-derived ceramic thin-film thermocouple exhibits good repeatability, stability, and thermoelectric potential output consistency. At 1200 °C, the peak output is 203 mV, and the average Seebeck coefficient is approximately 182 μV/°C. The temperature measurement error is 0.316%. In the 8-h drift test, the coefficient first increases at 1.26 °C/h and then steadily decreases at −0.63 °C/h. This polymer-derived ceramic thin-film thermocouple has excellent performance and can be applied to the in situ monitoring of thermal components in high-temperature and harsh environments, such as engines.

Nano cone ITO thin films prepared by pulsed laser deposition for surface measurement of high-temperature components

Semiconductor thin-film thermocouples (TFTCs) are widely used for temperature measurement of aero-engine components due to their large output and fast response. As a thermoelectric material, indium tin oxide (ITO) makes the device have very good thermoelectric merit because of its low resistivity, which is very suitable for the preparation of thin-film thermocouples. In this study, Pt-ITO thin-film thermocouple was fabricated on alumina ceramic substrate by pulsed laser deposition (PLD), and the microstructure and electrical properties of TFTCs prepared under different deposition conditions and annealing conditions were investigated. The results show that the ITO thin films prepared by PLD have a new type of nano cone structure and the resistivity of ITO thin films was only 2.76 × 10−4 Ω·cm when the substrate temperature was 600 °C. The Pt-ITO thin-film thermocouples can stable work for at 25–1300 °C and work in a short time at 1400 °C, and the average Seebeck coefficient is more than 50 µV/°C at 1300 °C. The response time of the prepared TFTC tested by pulsed laser is no more than 435 μs. These results provide an important basis for a potential application prospect of Pt-ITO TFTCs in the field of high-temperature measurement. It is further confirmed that the preparation of superior thermoelectric semiconductor materials by PLD is a promising method.

Electrical insulation improvement from interface regulation for high-temperature thin-film sensors on superalloy substrate

The stability and durability of insulation structure is crucial for the operation of thin-film sensors, especially at high temperature. However, it still faces great challenges in practical applications owing to the insulation failure during thermal cycles. In this study, an ALD Al2O3 film was introduced into the traditional TGO-sputtered Al2O3 insulation structure for interface regulation. After five thermal cycles up to 1000 °C, the modified insulation structure survived, while the control structure failed. The ALD Al2O3 layer could form denser equiaxed crystal during high-temperature crystallization, thereby preventing the propagation of cracks in sputtered Al2O3 due to volume shrinkage in phase transition. Furthermore, the ALD Al2O3 acted as a transition layer by forming semi-coherent interface with TGO Al2O3, stabilizing the multilayer insulation structure. Finally, Pt-PtRh thin-film thermocouples were fabricated on the modified insulation structure, which exhibited outstanding thermoelectric performance and stability at high temperature. Therefore, the interface regulation strategy proposed in this work could provide significant guidance for the development of high-temperature electrical insulation.

Thermoelectrical Properties of ITO/Pt, In2O3/Pt and ITO/In2O3 Thermocouples Prepared with Magnetron Sputtering

ITO/Pt, In2O3/Pt and ITO/In2O3 thermocouples were prepared by the radio frequency (RF) magnetron sputtering method. The XRD results showed that all the annealed ITO and In2O3 films annealed at high temperature present a cubic structure. Scanning electron microscope results showed that the thickness of the ITO and In2O3 films could reach 1.25 µm and 1.21 µm, respectively. The ITO/Pt and In2O3/Pt thin film thermocouples could obtain an output voltage of 68.7 mV and 183.5 mV, respectively, under a 900 °C temperature difference, and at the same time, the Seebeck coefficient reached 76.1 µV/°C and 203.9 µV/°C, respectively. For the ITO/In2O3 thermocouple, the maximum value of the output voltage was 165.7 mV under a 1200 °C temperature difference, and the Seebeck coefficient was 138.1 µV/°C. Annealing under different atmosphere conditions under 1000 °C, including vacuum, air and nitrogen atmospheres, resulted in values of the Seebeck coefficient that were 138.2 µV/°C, 135.5 µV/°C and 115.7 µV/°C, respectively.