Degradation of Gallium Nitride-Based Hall-Effect Sensors in High Temperature Environments

2020 ◽  
Author(s):  
Alexis Krone ◽  
Hannah Alpert ◽  
Satish Shetty ◽  
Debbie G. Senesky ◽  
Gregory Salamo ◽  
...  
Keyword(s):  
Gallium Nitride ◽  
High Temperature ◽  
Hall Effect ◽  
Electrical Response ◽  
Manufacturing Cost ◽  
Excellent Thermal Stability ◽  
Magnetic Field Sensors ◽  
X Ray ◽  
Wide Range ◽  
Hall Effect Sensors

Abstract Magnetic field sensors based on the Hall-effect have a variety of applications such as current sensing in power electronics and position and velocity sensing in vehicles. Additionally, they have benefits such as easy integration into circuits, low manufacturing cost, and linearity over a wide range of magnetic fields. However, in order to use these devices in an industrial or automotive setting, the effect of high temperatures on the reliability of the Hall-effect sensors needs to be evaluated. This study focuses on the effect of high temperature on the electrical and material properties of novel gallium nitride (GaN)-based Hall-effect sensors and the impacts on the reliability of these devices. Changes in device properties such as resistance and electrical response, as well as on the metallic contacts, are examined, using two sets of devices made with different substrates and contact metals. A probe station is used to characterize electrical responses, while an X-ray Photoelectron Spectrometer (XPS) and Electron-Diffuse X-ray (EDX) are used to characterize material interactions. The findings include saturation curves, the presence of gallium on the contacts of the octagonal device, and the activation energy of reaction responsible for resistance increase for the octagonal AlGaN/GaN devices. Additionally, the Greek cross AlGaN/GaN Hall sensors showed excellent thermal stability.

Degradation of Gallium Nitride-Based Hall Effect Sensors in High Temperature Environments

2021 ◽  
Author(s):  
Alexis Krone ◽  
Hannah Alpert ◽  
Satish Shetty ◽  
John Harris ◽  
David Huitink ◽  
...  
Keyword(s):  
Gallium Nitride ◽  
High Temperature ◽  
Hall Effect ◽  
Hall Effect Sensors

scholarly journals Quantifying phosphoric acid in high-temperature polymer electrolyte fuel cell components by X-ray tomographic microscopy

2014 ◽  
Vol 21 (6) ◽  
pp. 1319-1326 ◽  
Author(s):  
S. H. Eberhardt ◽  
F. Marone ◽  
M. Stampanoni ◽  
F. N. Büchi ◽  
T. J. Schmidt
Keyword(s):  
High Temperature ◽  
Fuel Cell ◽  
Phosphoric Acid ◽  
Polymer Electrolyte ◽  
Diffusion Layer ◽  
Gas Diffusion Layer ◽  
Gas Diffusion ◽  
X Ray ◽  
Wide Range ◽  
Cell Components

Synchrotron-based X-ray tomographic microscopy is investigated for imaging the local distribution and concentration of phosphoric acid in high-temperature polymer electrolyte fuel cells. Phosphoric acid fills the pores of the macro- and microporous fuel cell components. Its concentration in the fuel cell varies over a wide range (40–100 wt% H3PO4). This renders the quantification and concentration determination challenging. The problem is solved by using propagation-based phase contrast imaging and a referencing method. Fuel cell components with known acid concentrations were used to correlate greyscale values and acid concentrations. Thus calibration curves were established for the gas diffusion layer, catalyst layer and membrane in a non-operating fuel cell. The non-destructive imaging methodology was verified by comparing image-based values for acid content and concentration in the gas diffusion layer with those from chemical analysis.

Application of in situ Transmission Electron Microscopyfor Tribological Investigations of Magnetron Sputter Assisted Pulsed Laser Deposition of Yttria-stabilized Zirconia-gold Composite Coatings

2005 ◽  
Vol 20 (7) ◽  
pp. 1860-1868 ◽  
Author(s):  
J.J. Hu ◽  
A.A. Voevodin ◽  
J.S. Zabinski
Keyword(s):  
Electron Microscopy ◽  
High Temperature ◽  
Composite Coatings ◽  
Pulsed Laser ◽  
Yttria Stabilized Zirconia ◽  
Stabilized Zirconia ◽  
X Ray ◽  
Transmission Electron ◽  
Wide Range

Yttria-stabilized zirconia (YSZ)-Au composite coatings have great potential as solid film lubricants for aerospace applications over a wide range of environmental conditions. They were grown on steel disks or silicon wafers by pulsed laser ablation of YSZ and simultaneous magnetron sputtering of a Au target. Such a combination of ceramics with soft metals improved the toughness of the composite coating and increased its ability to lubricate at high temperature. Information on the time-dependent response of these microstructures to changes in temperature is essential to tribological investigations of high temperature performance. In situ transmission electron microscopy was used to directly measure the dynamic change of YSZ-Au coating structure at elevated temperatures. High-resolution electron microscopy and electron diffraction showed that amorphous YSZ-5 at.% Au coatings proceeded to crystallize under the irradiation of electron beams. Time varying x-ray energy dispersive spectra measured a loss of oxygen in the sample during about 10 min of irradiation with subsequent slight oxygen recovery. This behavior was related to the activation of oxygen diffusion under electron irradiation. X-ray diffraction patterns from vacuum annealed samples verified crystallization of the coatings at 500 °C. Real-time growth of Au nanograins in the sample was observed as the temperature was increased to 500 °C in a TEM specimen holder that could be heated. The grain growth process was recorded using a charge-coupled device camera installed on the transmission electron microscope. The crystallization and growth of zirconia and Au nanograins resulted in low friction during tribological tests. The nucleation of Au islands on heated ball-on-flat specimens was responsible for lowering friction.

A High-Temperature X-Ray Diffractometer Furnace Utilizing High-Frequency Heating*

1962 ◽  
Vol 6 ◽  
pp. 250-261 ◽  
Author(s):  
E. W. Franklin ◽  
S. M. Lang
Keyword(s):  
High Temperature ◽  
Temperature Control ◽  
High Frequency ◽  
Heating System ◽  
Integrated System ◽  
Operating Characteristics ◽  
Design Problems ◽  
X Ray ◽  
Wide Range ◽  
Frequency Heating

AbstractThe adaptation of high-frequency heating techniques to a vertical diffractometer will be discussed. The heating system functions as a. portion of an integrated system that provides a wide range of atmospheric and temperature control. Some of the design problems and their solutions and operating characteristics of the system will be described. The useful temperature range is from less than 200°C to greater than 1600°C, depending upon the fur-nace atmosphere and susceptors used. Gaseous pressures may be from vacuo of about 10−6 mm to about 30 psia; and, the sample may be heated in oxidizing, neutral, or reducing atmospheres.

Spectroscopy of high-temperature solar flare plasmas

1991 ◽  
Vol 336 (1643) ◽  
pp. 461-470 ◽  
Keyword(s):  
High Temperature ◽  
X Rays ◽  
Temperature Plasma ◽  
Flux Tubes ◽  
X Ray ◽  
Element Abundances ◽  
The Past ◽  
Hot Plasma ◽  
Wide Range ◽  
Flare Process

The past decade has seen great improvements in the quality of X -ray spectra of solar flares obtained from spacecraft. Such spectra show lines emitted by highly ionized atoms of abundant elements which make up high-temperature plasma contained within coronal magnetic flux tubes. This plasma is probably energized at or a little before the flare impulsive stage, as revealed by bursts of hard X-rays. Temperature and density conditions can be deduced from ratios of line intensities, as well as element abundances under certain conditions. In this paper, several examples of line ratios to deduce these are given. Analysis shows that there is a wide range of electron temperatures - generally from 2 x 10 6 K to 20 x 10 6 K - though sometimes even higher. Electron densities of around 10 17 -10 18 m -3 have been derived, higher values occurring at the flare peak or just before, and then declining. The physical conditions of the hot plasma are now precisely enough known from X -ray spectroscopy that models of flares which have been constructed in the past can be constrained. The most profitable direction for research in this area in the near future would in fact appear to be for a much better linking of the findings from X -ray spectra and modelling of plasma in flux tubes to understand better the flare process in general.

New high- and low-temperature apparatus for synchrotron polycrystalline X-ray diffraction

1998 ◽  
Vol 5 (3) ◽  
pp. 929-931 ◽  
Author(s):  
C. C. Tang ◽  
G. Bushnell-Wye ◽  
R. J. Cernik
Keyword(s):  
High Temperature ◽  
Low Temperature ◽  
Closed Cycle ◽  
X Ray Diffraction ◽  
X Ray ◽  
High Temperature Furnace ◽  
Wide Range ◽  
Powder Samples ◽  
Heater Coil ◽  
Temperature Furnace

A high-temperature furnace with an induction heater coil and a cryogenic system based on closed-cycle refrigeration have been assembled to enhance the non-ambient powder diffraction facilities at the Synchrotron Radiation Source, Daresbury Laboratory. The commissioning of the high- and low-temperature devices on the high-resolution powder diffractometer of Station 2.3 is described. The combined temperature range provided by the furnace/cryostat is 10–1500 K. Results from Fe and NH4Br powder samples are presented to demonstrate the operation of the apparatus. The developments presented in this paper are applicable to a wide range of other experiments and diffraction geometries.

scholarly journals In Situ High-Temperature X-ray Powder Diffraction and Infrared Spectroscopic Study of Melanterite, FeSO4·7H2O

Minerals ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 392
Author(s):  
Maria Lacalamita ◽  
Gennaro Ventruti ◽  
Giancarlo Della Ventura ◽  
Francesco Radica ◽  
Daniela Mauro ◽  
...  
Keyword(s):  
High Temperature ◽  
Powder Diffraction ◽  
Total Mass ◽  
Infrared Analysis ◽  
Infrared Spectroscopic Study ◽  
Rietveld Refinements ◽  
X Ray ◽  
Wide Range ◽  
Dta Curve

The thermal behavior of melanterite from the Fornovolasco mine (Tuscany, Italy) has been investigated via differential thermal analysis (DTA), thermogravimetry (TG), in situ high-temperature X-ray powder diffraction (XRPD) and Fourier-transform infrared spectroscopy (FTIR). The DTA curve showed endothermic peaks at 70, 100, 260, 500–560 and 660 °C whereas the TG curve evidenced a total mass decrease of ~68%, in keeping with the loss of all H2O and SO4 groups. Rietveld refinements were performed for all the collected patterns in the 25–775 °C range and converged at 1.57 ≤ R (%) ≤ 2.75 and 1.98 ≤ Rwp (%) ≤ 3.74. The decomposition steps FeSO4·7H2O → FeSO4·4H2O (25 ≤ T ≤ 50 °C) → FeSO4·H2O (50 < T ≤ 100 °C) → FeOHSO4 (75 < T ≤ 200 °C) → Fe2(SO4)3 (400 < T ≤ 500 °C) → Fe2O3 (500 < T ≤ 775 °C) were obtained. The high-temperature infrared analysis confirmed that melanterite undergoes a three-step dehydration in the 25–300 °C temperature range. The FeOHSO4 phase is stable over a wide range of temperature and transforms partially to Fe2(SO4)3 without the formation of Fe2O(SO4)2. The findings highlight a different behavior of the studied sample with respect to the synthetic salt.

High temperature Hall effect sensors based on AlGaN∕GaN heterojunctions

2006 ◽  
Vol 99 (11) ◽  
pp. 114510 ◽  
Author(s):  
Hai Lu ◽  
Peter Sandvik ◽  
Alexei Vertiatchikh ◽  
Jesse Tucker ◽  
Ahmed Elasser
Keyword(s):  
High Temperature ◽  
Hall Effect ◽  
Hall Effect Sensors

Application of TEM to Deformation, Wear, and Fracture of Ceramics

1974 ◽  
Vol 32 ◽  
pp. 472-473
Author(s):  
B. J. Hockey
Keyword(s):  
Wear Resistance ◽  
High Temperature ◽  
Mechanical Behavior ◽  
Brittle Materials ◽  
High Temperature Strength ◽  
Wide Range ◽  
Corrosive Environments ◽  
Further Development

Ceramics, such as Al2O3 and SiC have numerous current and potential uses in applications where high temperature strength, hardness, and wear resistance are required often in corrosive environments. These materials are, however, highly anisotropic and brittle, so that their mechanical behavior is often unpredictable. The further development of these materials will require a better understanding of the basic mechanisms controlling deformation, wear, and fracture.The purpose of this talk is to describe applications of TEM to the study of the deformation, wear, and fracture of Al2O3. Similar studies are currently being conducted on SiC and the techniques involved should be applicable to a wide range of hard, brittle materials.

TEM study of boron additions to cobalt aluminide

1988 ◽  
Vol 46 ◽  
pp. 546-547
Author(s):  
Gerald B. Feldewerth
Keyword(s):  
High Temperature ◽  
Turbine Engines ◽  
Major Drawback ◽  
University Of Missouri ◽  
Specific Strength ◽  
Aerospace Applications ◽  
Wide Range ◽  
Ordered Alloys ◽  
The University ◽  
Very High

In recent years an increasing emphasis has been placed on the study of high temperature intermetallic compounds for possible aerospace applications. One group of interest is the B2 aiuminides. This group of intermetaliics has a very high melting temperature, good high temperature, and excellent specific strength. These qualities make it a candidate for applications such as turbine engines. The B2 aiuminides exist over a wide range of compositions and also have a large solubility for third element substitutional additions, which may allow alloying additions to overcome their major drawback, their brittle nature.One B2 aluminide currently being studied is cobalt aluminide. Optical microscopy of CoAl alloys produced at the University of Missouri-Rolla showed a dramatic decrease in the grain size which affects the yield strength and flow stress of long range ordered alloys, and a change in the grain shape with the addition of 0.5 % boron.

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