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Feasibility of 4H-SiC p-i-n Diode for Sensitive Temperature Measurements between 20.5 K and 802 K
摘要： For the first time, we report on the performances of 4H-SiC pin-diode temperature sensors for operating temperatures between 20.5 K and 802 K. In this huge temperature range three ranges of performance were identified with the limit temperatures at 78.2 K and 176.3 K. In each of these ranges a different dominant current transport mechanism is shown and in the manuscript a detailed analysis and discussion is reported. The sensor performances were extracted from VD-T characteristics at different fixed ID values. In particular, at ID=1 μA and in the temperature range between 78.2 K and 802 K, we found a sensor sensitivity of 2.3 mV/K up to 3.4 mV/K with a rms temperature error, eT, of less than 4.2 K and the sensor shows an excellent linearity – quantified by the coefficient of determination R2 higher than 0.9993. For even lower temperatures (below 78.2 K), low measurement currents like 10 nA are required leading to a sensitivity of 5.8 mV/K, but a lower linearity (R2=0.9095) and a rms temperature error of 9.7 K which makes the sensor only partially usable in the temperature range between 20.5 K and 78.2 K. Finally, the sensor performances are compared to other state-of-the-art solutions.
关键词： Semiconductor device modelling,Cryogenic temperatures,Temperature sensors,4H-Silicon Carbide device,High temperatures,Semiconductor p-i-n diodes
更新于2025-09-23 15:22:29
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Measurement of Directional Spectral Emissivity at High Temperatures
摘要： Emissivity is a signi?cant parameter to describe the thermal radiation characteristics of the objects. It has important applications in thermal control of spacecrafts, highly ef?cient use of solar energy, buildings’ energy insulation and saving, and so on. Besides, more attention is attached to selective control of thermal emission by using micro-/nanostructures. In this work, to measure directional spectral emissivity, a measurement facility is developed which includes a sample heater with temperature control, a blackbody source, mirror assembly and a Fourier transform infrared spectrometer with different detectors. A sample heater is designed, and by using ceramic electric heaters, samples can be heated up to 1400 K at a high heating speed. And a new kind of water-cooled surface of the sample heating unit is designed to reduce the error by reducing the thermal radiation from surface of the heating unit so that measurement accuracy is improved. An electro-controlling rotating stage is adopted, and measuring angle is up to 60°. A SiC wafer is used as the reference to test the directional spectral emissivity measurement facility, and uncertainty is estimated.
关键词： High temperatures,Measurement,Directional emissivity,Spectra
更新于2025-09-23 15:21:21
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Thermoresistance of <i>p</i> -Type 4H-SiC Integrated MEMS Devices for High-Temperature Sensing
摘要： There is an increasing demand for the development and integration of multifunctional sensing modules into power electronic devices that can operate in high temperature environments. Here, the authors demonstrate the tunable thermoresistance of p-type 4H–SiC for a wide temperature range from the room temperature to above 800 K with integrated flow sensing functionality into a single power electronic chip. The electrical resistance of p-type 4H–SiC is found to exponentially decrease with increasing temperature to a threshold temperature of 536 K. The temperature coefficient of resistance (TCR) shows a large and negative value from (cid:1)2100 to (cid:1)7600 ppm K corresponding to a thermal index of 625 K. From the threshold temperature of 536–846 K, the electrical resistance shows excellent linearity with a positive TCR value of 900 ppm K. The authors successfully demonstrate the integration of p–4H–SiC flow sensing functionality with a high sensitivity of 1.035 μA(m s)^(-0.5) mW^(-1). These insights in the electrical transport of p–4H–SiC aid to improve the performance of p–4H–SiC integrated temperature and flow sensing systems, as well as the design consideration and integration of thermal sensors into 4H–SiC power electronic systems operating at high temperatures of up to 846 K.
关键词： thermoresistance,MEMS sensors,silicon carbide,high temperatures
更新于2025-09-19 17:15:36
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Giant Piezoelectricity of Ternary Perovskite Ceramics at High Temperatures
摘要： Here, novel ferroelectric ceramics of (0.95 ? x)BiScO3-xPbTiO3-0.05Pb(Sn1/3Nb2/3)O3 (BS-xPT-PSN) of complex perovskite structure are reported with compositions near the morphotropic phase boundary (MPB), and which exhibit a piezoelectric coefficient d33 = 555 pC N?1, a large-signal coefficient *d33 ≈ 1200 pm V?1 at room temperature, and a high Curie temperature TC of 408 °C. More interestingly, this ternary system exhibits a giant and stable piezoelectric response at 200 °C with a large-signal *d33 ≈ 2500 pm V?1, matching that of the costly relaxor-based piezoelectric single crystals at room temperature. The mechanisms of such giant piezoelectricity and its characteristic temperature dependence are attributed to the spontaneous polarization rotation and extension under an electric field and the MPB-related phase transition. The findings reveal that the BS-xPT-PSN ceramics constitute a new family of high-performance piezoelectric materials suitable for electromechanical transducers that can be operated at high temperatures (at 200 °C, or higher).
关键词： giant piezoelectricity,relaxor ferroelectric,high temperatures
更新于2025-09-19 17:15:36
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Introduction of a bifunctional cation affords perovskite solar cells stable at temperatures exceeding 80°C
摘要： Perovskite solar cells (PSCs) with high efficiencies have been reported in recent years. Consequently, the main obstacle that hinders their commercialization is their poor thermal stability. Here, we describe the introduction of an A-site cation (2-choloroethylammonium) that affords an ABX3 perovskite, which is stable at high temperatures (> 80°C) while achieving efficiencies > 19% in methylammonium lead iodide (MAPI)-based PSCs.
关键词： perovskite solar cells,efficiency,high temperatures,bifunctional cation,thermal stability
更新于2025-09-12 10:27:22
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Analysis of diamond wheel wear and surface integrity in laser-assisted grinding of RB-SiC ceramics
摘要： Laser-assisted grinding provides a promising solution for achieving cost-e?cient machining of hard and brittle materials. However, the heat generated by laser may cause the wear of diamond grinding wheel, including the wear of both diamond grits and bond material. Consequently, wheel wear has a knock-on e?ect on the ground surface roughness. Moreover, the laser irritation may also induce damage in the machined surface. This paper focuses on the investigation of wear of diamond grinding wheel and surface integrity in laser-assisted grinding of RB-SiC ceramics. Di?erent temperatures were obtained by setting the laser power to explore the in?uence of heat on wheel wear and surface integrity. The wear modes and mechanism of the diamond grits and bond material were analyzed by combination of SEM detection and energy dispersion spectrum analysis. The results revealed that adhesion and pullout of diamond grits in laser-assisted grinding were the remarkable di?erence from those in conventional grinding due to the thermal softening of both RB-SiC specimen and bond material of the grinding wheel. Surface roughness was then improved owing to the increase in active grits. The Raman spectra of the machined surface also revealed di?erent stress conditions and microstructures of the Si and SiC Phase in RB-SiC ceramics. These results provided insight on quality control in laser-assisted machining of RB-SiC ceramics.
关键词： Grinding wheel wear,Surface integrity,Laser-assisted grinding,High temperatures
更新于2025-09-11 14:15:04
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Energy Coupling of Laser Radiation on AISI 304 Stainless Steel: Effect of High Temperatures and Surface Oxidation
摘要： The industrial application of laser materials processing methods is still far ahead of research into the physical phenomena occurring during these processes. In particular, the effect of high temperatures on the energy coupling of laser irradiation of metals is poorly understood. However, most processes in laser materials treatment involve temperatures above the melting point or even cause evaporation. This study therefore evaluates the effect of high temperatures on the energy coupling efficiency of stainless steel experimentally for three typical laser wavelengths (515 nm, 1.07 μm, 10.6 μm). As a result, it is shown that the effect of temperature on the energy coupling efficiency depends on the wavelength. In this context the relevance of the X-point phenomenon known from the emissivity theory could be demonstrated for laser material processing. Further, the effect of a process-induced surface oxidation is analyzed. At temperatures above 650°C the energy coupling efficiency dramatically increases to around 65% at melting point and stays at this high level even in the liquid phase.
关键词： energy coupling efficiency,absorptivity,high temperatures,surface oxidation,laser material processing
更新于2025-09-11 14:15:04
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Phonon thermodynamics and elastic behavior of GaN at high temperatures and pressures
摘要： The effects of temperature and pressure on the phonons of GaN were calculated for both the wurtzite and zinc-blende structures. The quasiharmonic approximation (QHA) gave reasonable results for the temperature dependence of the phonon DOS at zero pressure but unreliably predicted the combined effects of temperature and pressure. Pressure was found to change the explicit anharmonicity, altering the thermal shifts of phonons and more notably qualitatively changing the evolution of phonon lifetimes with increasing temperature. These effects were largest for the optical modes, and phonon frequencies below approximately 5 THz were adequately predicted with the QHA. The elastic anisotropies of GaN in both wurtzite and zinc-blende structures were calculated from the elastic constants as a function of pressure at 0 K. The elastic anisotropy increased with pressure until reaching elastic instabilities at 40 GPa (zinc blende) and 65 GPa (wurtzite). The calculated instabilities are consistent with proposed transformation pathways to rocksalt GaN and place upper bounds on the pressures at which wurtzite and zinc-blende GaN can be metastable.
关键词： phonon thermodynamics,high pressures,elastic anisotropy,anharmonicity,high temperatures,GaN,elastic behavior,quasiharmonic approximation
更新于2025-09-09 09:28:46
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Electromagnetic Acoustic Transducers Applied to High Temperature Plates for Potential Use in the Solar Thermal Industry
摘要： Concentrated Solar Plants (CSPs) are used in solar thermal industry for collecting and converting sunlight into electricity. Parabolic trough CSPs are the most widely used type of CSP and an absorber tube is an essential part of them. The hostile operating environment of the absorber tubes, such as high temperatures (400–550 °C), from creep, contraction/expansion, and vibrations, may lead them to suffer thermo-mechanical fatigue, and hot corrosion. Hence, their condition monitoring is of crucial importance and a very challenging task as well. Electromagnetic Acoustic Transducers (EMATs) are a promising, non-contact technology of transducers that has the potential to be used for the inspection of large structures at high temperatures by exciting Guided Waves. In this paper, a study regarding the potential use of EMATs in this application and their performance at high temperature is presented. A Periodic Permanent Magnet (PPM) EMAT with a racetrack coil, designed to excite Shear Horizontal waves (SH0), has been theoretically and experimentally evaluated at both room and high temperatures.
关键词： non-destructive testing,high temperatures,Electromagnetic Acoustic Transducer (EMAT),solar thermal plants,guided waves
更新于2025-09-09 09:28:46