bluuebunny/crossref_metadata_2025 huggingface dataset:
The Effect of CaO Coatings on the Oxidation Behaviour of Polycrystalline Nickel between 800 and 1200 °C
Authors: Halem N. , Cieniek Lukasz , Kusinski J. , Baldinozzi Gianguido , Petot C. , Petot-Ervas Georgette
Published: March 2009

The present study is concerned with the influence of sputter-coatings CaO on the
oxidation behavior of Ni polycrystals. The experiments were performed in air, in the temperature
range 800°-1200°C. Below 1200°C, CaO coatings reduce the oxidation rate, while this beneficial
effect disappears at 1200 °C. The oxidized specimens were examined by SEM and X-Ray
diffraction, but also by EPMA depth profiling to evaluate the scale composition. Furthermore,
electrical conductivity measurements and kinetic demixing studies were carried out on Ca-doped
NiO single crystals, to get a better insight regarding the transport processes involved during
oxidation. These last results show that the key features allowing to explain the effect of CaOcoatings
on the oxidation rate of Ni are the influence of calcium on the increase of the dissociation
pressure of NiO, which delays the oxidation of nickel, the kinetic demixing of the cations, which
controls the distribution of CaO precipitates in the scale responsible for blocking effects, and the
increase of the diffusion coefficient of both the cations and the cationic vacancies, which play a
decisive role at high temperature, when the scale growth is dominated by lattice diffusion.
The Effect of Thermal Expansion on Spallation Behavior of Fe-Base Alumina-Forming Alloys
Authors: Pint Bruce A. , Porter W.D. , Wright Ian G.
Published: March 2009

Long-term cyclic oxidation behavior was compared for commercial FeCrAl alloys and
model Fe-Al and FeCrAl alloys, and their coefficients of thermal expansion (CTE) were measured.
For single-phase disordered (ferritic) Fe(Al) alloys, the CTE increased only slightly with Al content
and was similar to that of FeCrAl alloys. More significant CTE increases were observed at ≥20%Al,
as intermetallic phases, Fe3Al and FeAl, formed. As expected, the intermetallic compositions
showed increased oxide spallation rates during cyclic oxidation at 1100° and 1200°C. However,
after extensive spallation and loss of Al from the substrate, the compositions of Fe3Al and FeAl
specimens entered the ferritic phase field, and the amount of scale spallation decreased. Among
commercial oxide dispersion strengthened (ODS) FeCrAl alloys, a composition containing Mo
(ODM751) exhibited the lowest thermal expansion and showed the slowest degradation rate in
long-term testing at 1100°C. The concept of minimizing CTE as a route for alloy development was
investigated.
Void Formation and Filling under Alumina Scales Formed on Fe-20Cr-5Al Alloy Thin Foils
Authors: Potter D.J. , Tatlock G.J.
Published: March 2009

The oxidation behaviour and the subsequent chemical failure of a Fe-20Cr-5Al based
alloy were studied at 1200°C in laboratory air, at times of up to 700 hours. Tests on 70 micron thick
foils, showed void formation at the metal/oxide interface soon after the aluminium content in the
alloy dropped below a critical level (≤0.5 wt%). At this stage, the alloy could no longer sustain
alumina scale formation and resulted in the initiation and development of a Cr-rich sub-layer. This
chromia layer was found to be continuous and of a uniform thickness. As the sub-layer formed,
voids were also observed at the metal/oxide interface. The voids were found to fill with chromia
after further exposure. It is thought that the change in oxide growth mechanism from alumina to
chromia growth is responsible for the void formation. This also explains the lack of void formation
during the sustainable growth of the alumina scale.
The introduction of silicon to the Fe-20Cr-5Al based alloy via a diffusion couple was found to
significantly influence the oxidation behaviour of the thin foils. Void formation was observed
directly beneath the alumina scale and filled voids were now found to contain silicon oxide rather
than chromia. The void filling mechanism also appeared to be different. With chromia filled voids,
the filling commenced from the underside of the oxide, with the oxide growing inwards, while silica
containing voids were filled by silica growing outwards into the void from the substrate.
Throughout the study, optical and scanning electron microscopes were used to analyse all stages of
oxidation and the subsequent failure of the thin foil samples. EBSD was also used to generate a
more comprehensive analysis of selected locations.
Manganese Effect on Isothermal High Temperature Oxidation Behaviour of AISI 304 Stainless Steel
Authors: Riffard Frédéric , Buscail Henri , Rabaste F. , Caudron Eric , Cueff Régis , Issartel Christophe , Karimi N. , Perrier Sébastien
Published: March 2009

Chromia-forming steels are excellent candidates to resist to high temperature oxidizing
atmospheres because they form protective oxide scales. The oxide scale growth mechanisms are
studied by exposing AISI 304 stainless steel to high temperature conditions in air, and the analyses
were carried out by means of thermogravimetry and in situ X-rays diffraction. The in situ XRD
analyses carried out during high temperature AISI 304 steel oxidation in air reveals the accelerated
growth of iron-containing oxides such as hematite Fe2O3 and iron-chromite FeCr2O4, when the
initial germination of the oxide layer contains the presence of a manganese-containing spinel
compound (1000°C). When the initial growth shows the only chromia formation (800°C), hematite
formation appears differed in time. Protection against corrosion is thus increased when the initial
germination of manganese-containing spinel oxide is inhibited in the oxide scale.
Solid Reactions between Enamel and O-Phase Ti-Al-Nb Intermetallics at 800 °C
Authors: Zheng D.Y. , Xiong Yu Ming , Zhu Sheng Long , Wang Fu Hui , Wu Wei Tao
Published: March 2009

The specimens of O-phase Ti-22Al-25Nb (at%) intermetallics coated with silica-based
enamel received mass gains of about 1 mg/cm2, after 300 h of oxidation or hot corrosion at 800 °C.
These rates were much faster than the growth rates of silica films at the same temperature. To
understand this phenomena, the specimens were analyzed using SEM, XRD, EPMA and TEM. An
oxide layer with thickness of several μm was observed at the enamel/substrate interface of the coated
specimens after either oxidation or hot corrosion. XRD and TEM analysis revealed the newly formed
oxide layer was composed of α-Al2O3, Al2SiO5, Al2TiO5, rutile-TiO2 and NbO2. It was shown by
EPMA profiling that an Al-depleted zone was located just beneath the oxides. It was proposed that
the solid reactions between the enamel coating and the O-phase Ti-Al-Nb played important roles for
the oxidation and hot corrosion behavior of the coated specimens.
Scale Growth on Austenitic Alloys under KCl Deposits at 500°C
Authors: Andersson Petter , Norell Mats
Published: March 2009

The scale growth on two austenitic alloys, Alloy 310 and Sanicro 28, under KCl deposits
was examined. This is relevant to the long term corrosion of superheater tubes in biofuel
combustion. Coupons were encapsulated in tablets so that 1 mm of KCl with a relative density of
91% covered the metal. Samples were tested at 500°C in 5%O2-10%H2O-N2 for 24, 168 and 672
h. After exposure the salt was broken off and the scale was characterised by using SEM-EDX and
AES. After 24 h a 50 nm thick oxide surrounded 500 nm thick chromates on the surface. No oxide
layer was detected under the chromates and no Cl was found under either layer. The chromate
growth requires lateral transportation of Cr along the surface. This reduces the protectiveness of the
oxide and accelerates the formation of less protective Fe rich oxides. The formation of chromates
also releases HCl inside the KCl tablet. The chromates did not grow significantly between 24 and
168 h, but the oxide grew equally thick beneath and between them and Cl was enriched around the
metal oxide interface. After 672 h the oxides were about 5 μm thick and only few chromates were
seen. Crystals of KCl formed in areas with thick porous and Fe rich oxides on both alloys.
Electrochemical Study of the Corrosion of Metals in Molten Fluorides
Authors: Fabre Stéphanie , Cabet Céline , Cassayre Laurent , Chamelot Pierre , Finne Jörgen , Noël Didier , Taxil Pierre
Published: March 2009

Resistance to corrosion of the structural materials is a key factor for nuclear applications
that use molten fluorides. Low chromium, nickel-base alloys are regarded as the most suitable
metallic materials. In a first approach, corrosion of some pure metallic constituents Ni, Mo, W and
Fe, was studied by electrochemical techniques. Linear voltammetry was applied in LiF-NaF and
LiF-AlF3, in the temperature range 900-1100°C.
The relative stability of the metals in LiF-NaF is established. To determine the corrosion current
density, three methods are presented, two based on the Tafel extrapolation method and the third one
being the polarization resistance method. Results regarding corrosion rates are compared. Two
corrosion behaviors are observed: on the one side, Ni, Mo and W and on the other side Fe. The
difference might come either from different corrosion mechanisms or from a different number of
exchanged electrons. The corrosion rate increases with temperature following the Arrhenius law.
However, further experiments are needed in order to identify the key parameters that influence the
corrosion in the different melts.
Rumpling of Platinum Modified Aluminide Coatings during Thermomechanical Testing
Authors: Dryepondt Sébastien , Clarke David R.
Published: March 2009

The evolution in surface morphology of platinum modified nickel aluminide (Ni,Pt)Al
oxidation coatings during thermo-mechanical testing has been evaluated. One type of test consisted
of cyclic oxidation between an upper temperature of 1150°C and a lower temperature varying from
room temperature to 1050°C. The other type of test was cycling between 1000°C/1150°C under an
applied compressive stress. Profilometry using optical interferometry was used to quantify the
surface “rumpling”. First and second-order statistical parameters including RMS roughness and the
auto-correlation function were calculated from the profilometry measurements. The results indicate
that the grain structure of the aluminide coating plays a major role in the early stages of rumpling
and set its wavelength. Also, the superimposed compressive stress during thermal cycling leads to
an asymmetry in the rumpling pattern with respect with the loading axis as well as cracking along
the applied stress direction.
Mechanism of Catalytic Coke Formation and Some Means to Limit it in Refinery Processes
Authors: Ropital François , Bonnet Frédéric
Published: March 2009

The formation of carbon filaments which occurs at carbon activities ac > 1 in a range of
temperatures 450-700°C is a major problem in many chemical, petrochemical and refinery
processes where hydrocarbons or other strongly carburizing atmospheres are involved. An
excessive carbon deposition causes deterioration of the furnace alloys, such as an important
migration of carbon into the alloys. In order to better control and limit this deterioration, this work
has been performed to on one side get a more accurate understanding of the mechanisms of
formation of catalytic coke and on the other side to find remedies as the injection of selected
additives in the feed. Thermogravimetric analyses (TGA) were performed on iron samples in
simulated conditions of isobutane dehydrogenation. X ray diffraction (XRD) and scanning electron
microscopy examinations were used to identify the different steps during the formation of the
catalytic coke. The selection of appropriate remedies to reduce the catalytic coke deposition,
requires accurate understanding on both mechanisms of the catalytic particles formation and of the
growth of the graphite filaments. We have studied the first steps of the catalytic coke formation on
high purity iron that has been previously reduced or oxidised. The comparison of the catalytic coke
deposition kinetics indicates that the mass gain is much faster on a pre oxidised state than on a
reduced one.
In refinery and petrochemical processes, several methods can be selected in order to limit the
deposition phenomena of catalytic coke: selection of an appropriate metallurgy, protection of the
surfaces by application of coatings, injection of additives with the feed. Steric inhibitors (that block
the adsorption sites and slow down the germination and diffusion steps) such as sulfur additives are
currently industrially used but special care has to be taken in order to prevent consequential
secondary effects such as, for catalytic refinery process, the deactivation of catalysts. Based on
TGA experiments, the accurate amount of inhibitor to be injected has been selected regarding the
oxidising state of the iron surface.
Platinum Diffusion and Microstructure Change in a Single Crystal Superalloy and Nickel-Based Model Alloys at 1000°C
Authors: Ford Stewart , Hayashi Shigenari , Narita Toshio
Published: March 2009

Single crystal superalloy TMS82+ and model alloys of Ni-12Al and Ni-6Cr-8Co-12Al
were electroplated with 5-6μm of platinum and heat treated at 1000°C for up to 100hrs. In the model
alloys the platinum concentration gradient in the interdiffusion region caused uphill diffusion of
aluminium. The subsequent surface enrichment led to formation of aluminium-rich γ′ phase. In
TMS82+ superalloy inward diffusion of platinum resulted in loss of the γ/γ′ microstructure and
formation of new γ and γ′ grains. The initial dissolution of the γ′ cubes was due to the outward
diffusion of aluminium. Again, the presence of a platinum gradient in the interdiffusion region
resulted in uphill diffusion of aluminium and a net increase in aluminium content at the alloy surface,
leading to a near-surface single-phase γ′ layer being formed, however topologically close-packed
(TCP) phase formation was not observed.
Evaluation of Al2O3 MOCVD Coating for Titanium Alloys Protection under Severe Conditions at High Temperature
Authors: Béguin Jean Denis , Samelor Diane , Vahlas C. , Gleizes Alain , Petit J.A. , Sheldon B.
Published: March 2009

The corrosion resistance of MOCVD Al2O3 coating system was investigated to protect a
TA6V Alloy under hot salt corrosion conditions: This coating was corroded with a salt deposit
without mechanical loading at 480°C during 100 h. Corrosion products formed in salted areas were
studied by Energy Dispersive Spectroscopy (EDS). Although all coated specimens were damaged
with corrosion products presence in salted area, Al2O3 coatings showed the lowest salt damage on
titanium substrate after a metallographic cross section observation compared to uncoated ones. As
well as these interesting experimental results, coated specimens exhibit a good adherence on
titanium substrate
Effect of Lanthanum Sol-Gel Coating on the Oxidation Behaviour of the AISI 304 Steel at 1000°C
Authors: Karimi N. , Buscail Henri , Riffard Frédéric , Rabaste F. , Cueff Régis , Issartel Christophe , Caudron Eric , Perrier Sébastien
Published: March 2009

The aim of the present work is to investigate the effect of Lanthanum surface addition on
the oxidation behaviour of the AISI 304 stainless steel, in air, at 1000°C. The in situ X-ray
diffraction (XRD) analyses on the blank steel reveal that after the first 10h oxidation, a change in
the structural composition of the oxide scale occurs. During the first ten hours oxidation an initial
growth of chromia and Mn1,5Cr1,5O4 is observed. After 10 h oxidation, chromia is not detected
anymore and iron-containing oxides such as hematite (Fe2O3) and iron chromite (FeCr2O4) are
observed in the outer part of the scale. With blank AISI 304 specimens, the iron-containing oxides
are generally not very protective and show severe spallation during cooling to room temperature
due to thermal stresses. They do not allow a good adherence of the corrosion layer under thermal
cycling. On the Lanthanum coated AISI 304 Stainless Steel the oxidation rate is 10 times lower. In
situ XRD analyses show the absence of iron containing oxides. It reveals the formation of a fine
convoluted Cr2O3 layer associated with the formation of the mixed oxides Mn1,5Cr1,5O4 and LaCrO3.
LaCrO3 is found to be located at the oxide/steel interface. Our results show that, even though the
scale formed under isothermal conditions is not composed of iron containing oxides, Lanthanum
sol-gel coating does not prevent spallation during thermal cycling at 1000°C.
High Temperature Corrosion of the Si-Mo Cast Iron in Exhaust Atmosphere
Authors: Dawi Kamel , Favergeon Jérôme , Moulin Gérard
Published: March 2009

The SiMo cast iron is a spheroidal graphite cast iron which major alloying elements are
silicon and molybdenum. This alloy is currently used in diesel engines as part of exhaust gas system
like exhaust manifold or turbocharger housing components. It is then designed to work at high
temperature under corrosive atmosphere. However, this alloy presents sometimes unusual high
corrosion rates, and it is thus advisable to define the critical conditions leading to this type of
problem.
In the present study, the SiMo cast iron is tested in complex atmospheres containing N2, O2, SO2,
CO2 and H2O in a temperature range lying between 300°C and 600°C. SEM observations and EDX
and XRD analyses allow to qualify the nature of the corrosion products. Some thermodynamic
calculations complete the experimental results.
Three experimental parameters are especially studied in this work: the temperature of the isothermal
corrosion tests, the presence of water vapour and the SO2 content in the gas mixture. The main
results show that the corrosion products are metallic sulphides, sulfates and oxides.
When sulphides and / or sulfates are present, the corrosion scale does not ensure a sufficient
protection of the substrate and it is necessary to find conditions where only oxides are present. Such
conditions are obtained for the highest temperature used in this study (600°C), or with highly
oxidant atmospheres.
Investigation of Thin Coatings from Mn-Co-Fe System Deposited by PVD on Metallic Interconnects for SOFC Applications
Authors: Mardare Cezarina C. , Spiegel Michael , Savan Alan , Ludwig Alfred
Published: March 2009

Ternary Mn-Co-Fe metallic thin films were deposited by RF-magnetron co-sputtering on
SiO2/Si wafers and on ZMG232L (Hitachi Metals®), a special ferritic stainless steel for Solid Oxide
Fuel Cell applications. The deposition was followed by heat treatment in an oxidizing atmosphere
in order to convert the metallic thin films to (Mn,Co,Fe)3O4 spinel oxides. Coated and uncoated
steel samples were analyzed after 1 h heat treatment in order to confirm the presence of the spinel
structure on top of the steel, as well as to investigate and characterize the growth of oxides, namely
(Mn,Cr)3O4 and Cr2O3, at the internal steel/coating interface. From Grazing Incidence X-ray
Diffraction (GI-XRD) investigations together with Energy Dispersive X-ray analysis – Scanning
Electron Microscopy and Time of Flight – Secondary Ions Mass Spectroscopy sputtering depth
profiling the presence of well adherent (Mn,Co,Fe)3O4 coatings with approximately 500 nm
thickness and a grain size of about 150 nm was confirmed. After the preparation annealing, some
samples were heat-treated in simulated cathodic atmospheres at 800 °C for 500 h in order to assess
the stability of the coatings. GI-XRD spectra still showed the presence of the protective coatings,
however sputtering depth profile analysis indicated the presence of Cr on the surface.
Investigation of the Development Processes of Self-Organizing, Protective Oxide Scales and Wear Resistant Surface Layers on the Fe-44%Cr-1%Ni-4%Al-0.3%La Alloy
Authors: Tsurtsumia Olga , Kutelia Elguja , Bulia Boris , Mikadze Omar
Published: March 2009

Using the methods of scanning electron microscopy (SEM), Auger electron spectrometry
(AES), fast electron diffraction (FED) in the “on reflection” regime and wavelength dispersive
spectrometry (WDS) a complex investigation of the hierarchical sequence of amorphous Beilby
layer formation has been studied due to the self-organizing dissipative processes, associated with
extensive cold work, on the surface of an Fe-Cr-Ni-Al-La alloy, with high (>40%) chromium
content. It was established that, the surface layer (≤1μm thickness) of the mechanically polished
specimen of Fe-44%Cr-1%Ni-4%Al-0.3%La alloy consists of the amorphous Beilby layer and that
its adjacent matrix layer, crushed due to the plastic deformation, formed an entropy “excited”
functional system, which at the temperature of 1200°C in laboratory atmosphere permits the
formation of an oxide surface layer with a micro-wrinkles modulated structure of uniform thickness,
in the form of mixture of nanocrystallites (100÷500nm) made of oxides of atoms constituting the
basic metallic matrix. Beneath this layer a thin alumina scale is observed to form. Increasing the
oxidation temperature causes the regrowth of nanocrystallites and also the recrystallization
processes, accompanied by solid-phase reactions between oxide nano-particles. This leads to scale
delamination at the superficial oxide thin uniform alumina layer interface. The Al2O3 layer is
characterized by high adherence with metallic substrate and provides protective features against
both high temperature (1200°C) oxidation of the matrix and resistance to abrasion. By the
pretreatment at 1200°C of the investigated alloy’s surface modified specimens, there forms a low
thickness (several microns) scale which has ultra fine graininess (~1μ) with no porosity and blocked
grain boundaries short-circuit diffusion paths. This gives to the scale the ability to protect the
metallic matrix against high temperature gas (and other aggressive environment) corrosion.
Influence of Micro-Structure on Oxidation Behavior of a Ni-Based Superalloy at 1000°C
Authors: Liu Li , Li Ying , Wang Fu Hui
Published: March 2009

The isothermal and cyclic oxidation behaviors of a Ni-based superalloy with singlecrystalline
(SC), polycrystalline and nanocrystalline (NC) structures were studied at 1000°C.
Results indicated that a uniform oxides scale consisted of external Cr2O3 with little TiO2 and
internal continuous Al2O3 formed on SC alloy. A non-uniform external oxide of which some
locations were nodule-like scale was formed on surface of cast alloy. The nodule-like parts
consisted of TiO2, Cr2O3 and serious internal oxidation of Al, and rest flat surface was a Cr2O3 and
Al2O3 layer. A continuous Al2O3 layer formed on the sputtered NC coating. The micro-structure
influenced the oxidation mechanism and resulted in different oxide scale formed on three materials,
which greatly influenced materials’ oxidation and cyclic-oxidation resistance.
Yttrium Implantation and Manganese Addition Element Effects on the High Temperature Oxidation Resistance of a Model Steel
Authors: Caudron Eric , Cueff Régis , Issartel Christophe , Karimi N. , Riffard Frédéric , Perrier Sébastien , Buscail Henri
Published: March 2009

Manganese addition and subsequent yttrium implantation effects on extra low carbon
steel were studied by Rutherford Backscattering Spectrometry (RBS), Reflection High Energy
Electron Diffraction (RHEED), X-ray Diffraction (XRD) and Glancing Angle X-ray Diffraction
(GAXRD). Thermogravimetry and in situ X-Ray Diffraction at 700°C and PO2=0.04 Pa for 24h
were used to determine the manganese alloying addition and subsequent yttrium implantation
effects on reference steel oxidation resistance at high temperatures. This study clearly shows the
combined effect of manganese alloying addition and subsequent yttrium implantation which
promotes the formation of several yttrium mixed oxides seem to be responsible for the improved
reference steel oxidation resistance at high temperatures.
Oxidation of Some Titanium Alloys in Air at Elevated Temperatures
Authors: Godlewska E. , Mitoraj M. , Jajko B.
Published: March 2009

This paper presents comparative studies on the performance of two titanium alloys (Ti-
6Al-1Mn, Ti-45.9Al-8Nb) in an oxidizing atmosphere at 700 oC and 800 oC. Testing procedure
comprised thermogravimetric measurements at a constant temperature and in thermal cycling
conditions (1-h and 20-h cycles at constant temperature followed by rapid cooling). The overall
duration of the cyclic oxidation tests was up to 1000 hours. The oxidized specimens were analyzed
in terms of chemical composition, phase composition, and morphology (SEM/EDS, TEM/EDS,
XRD). The extent and forms of alloy degradation were evaluated on the basis of microscopic
observation of specimen fractures and cross-sections. Selected specimens were examined by means
of XPS, SIMS and GDS. Oxidation mechanism of Ti-46Al-8Nb was assessed a two-stage oxidation
method using oxygen-18 and oxygen-16. Apparently, the oxidation of this alloy proceeded in
several stages. According to XPS, already after quite short reaction time, the specimens were
covered with a very thin oxide film, mainly composed of aluminum oxide (corundum). A thicker
layer of titanium dioxide (rutile) developed underneath. These two layers were typical of the
oxidation products formed on this alloy, even when tested in thermal cycling conditions. In general,
the scale had a complex multilayer structure but it was thin and adherent. Under the continuous
layer of titania, there was a fine-grained zone composed of mixed oxides. The alloy/scale interface
was marked with niobium-rich precipitates embedded in a titanium-rich matrix. There were some
indications of secondary processes occurring under the initial continuous oxide layers (e.g.
characteristic layout of pores or voids). Thickness of inner scale layers clearly increased according
to parabolic kinetics, while that of the outer compact layer (mainly TiO2) changed only slightly. The
distribution of oxygen isotopes across the scale/alloy interface indicated two-way diffusion of the
reacting species – oxygen inward and metals outward diffusion. Silicon deposited on Ti-6Al-1Mn
alloy positively affected scale adhesion and remarkably reduced alloy degradation rate.
Monotonic Strength Properties of Siberian Yellow Pine
Authors: Kettunen Pentti O. , Vuoristo Taina , Kaasalainen Terho
Published: March 2009

Strength values of the sapwood of Siberian yellow pine were measured in a system with orthogonal coordinates along the axial, radial, and tangential directions of the cell structure. Highest strength was the axial normal strength and lowest the tangential normal strength. The difference between these two values was 87-fold. Shear strength values remained between the two normal strength values. The highest shear strength appeared in tangential direction across the reinforcing fibers, i.e., on the plane perpendicular to the axial direction. Lowest shear strength appeared in tangential direction on the plane perpendicular to radial direction. The variations are due to orientation of cells and of fiber reinforcement in the cell wall laminas, especially in the middle layer of the secondary cell wall.
Comparative Evaluation of Anode Layers on the Electrical Characteristics of High Voltage 4H-SiC PiN Diodes
Authors: Losee Peter A. , Wang Y. , Li Can Hua , Sharma Santosh K. , Bhat I. , Chow T. Paul , Gutmann Ronald J.
Published: March 2009

The impact of anode layers on the electrical characteristics of 10kV 4H-SiC PiN diodes
has been evaluated in this work. Co-fabricated diodes with various epitaxial anode layer designs as
well as those employing P+ implanted injecting layers are used to experimentally investigate the
device conduction mechanisms. The role of the injecting layer is demonstrated via electrical
characteristics and numerical simulations, showing the importance of maintaining sufficient carrier
recombination lifetime in the device anode region.
Novel SiC Zener Diodes with High Operating Temperature of 300°C and High Power Density of 40 kW/cm2
Authors: Ishii Ryosuke , Nakayama Koji , Tsuchida Hidekazu , Sugawara Yoshitaka
Published: March 2009

This paper reports on the achievement of high-power 4H-SiC Zener diodes which have a
high-doped pn junction with a large active area of 4 mm x 4 mm. The temperature coefficient of the
breakdown voltage is as small as 5.7x10-5 1/K (positive) in the temperature range 20-300°C. In
addition, reverse power capabilities of 6.3 kW (40 kW/cm2) at 20°C and 6.0 kW (38 kW/cm2) at
300°C during rectangular pulsed power operation (tw = 1 ms) have been achieved without device
failure.
Annealing Effect on Characteristics of p+n 4H-SiC Diode Formed by Al Ion Implantation
Authors: Satoh Masataka , Miyagawa Shingo , Kudoh T. , Egami Akihiro , Numajiri Kenji , Shibagaki Masami
Published: March 2009

The I-V characteristics of p+n 4H-SiC diode formed by Al ion implantation have been
investigated as a function of annealing temperature. Al ions are implanted at the elevated sample
temperature of 500 oC in order to fabricate p-type doped layer on the n-type epitaxial layer, grown on
n+ 4H-SiC substrate. The implanted sample is annealed using electron bombardment annealing
system in the annealing temperature ranging from 1700 to 1900 oC. The Al implanted sample,
annealed below 1800 oC shows the deteriorated I-V characteristics in which the forward current
includes the resistive current components and the reverse current is in the order of 10-4 A/cm2. The
p+n diode formed by annealing at 1900 oC reveals the forward current without extra-current
components and the reverse current as low as 10-6 A/cm2. It is suggested that the annealing above
1900 oC is effective in reducing the implantation-induced defect at the interface between Al implanted
p+ layer and the underlying n-type epitaxial layer.
Room Temperature Annealing Effects on Leakage Current of Ion Implanted p+n 4H-SiC Diodes
Authors: Moscatelli Francesco , Bergamini Fabio , Poggi Antonella , Passini Mara , Tamarri Fabrizio , Bianconi Marco , Nipoti Roberta
Published: March 2009

The current-voltage characteristics of Al+ implanted 4H-SiC p+n junctions show an
important reduction of leakage currents with diode aging at room temperature. The case of a family of
diodes that immediately after manufacture had forward current density increasing from 10-9 to
10-6 A/cm2 when biased from 0 and 2 V, and had a reverse leakage current density of @ 5×10-7 A/cm2
when biased at 100 V, is here presented and discussed. During diode manufacturing a post
implantation annealing at 1600 °C for 30 min was followed by a 1000 °C 1 min treatment for metal
contacts alloying. After 700 days of storage at room temperature, the diode reverse current density
reached an asymptotical value of @ 4×10-11 A/cm2 that is four order of magnitude lower than the
initial one. A 430 °C annealing that was made after 366 days is responsible of a decrease of one of
these four orders of magnitude, but it does not interrupt the decreasing trend versus increasing time.
This same annealing has been effective also for minimizing forward current for bias < 2 V, and
sticking the diode turn-on voltage on 1.4 V and the current trend on an ideality factor of 2. These
results show that in Al+ implanted 4H-SiC p+n junction there are defects that have an annihilation
dynamic at very low temperatures, i.e. room temperature and 430 °C.
High Quality Epitaxial Growth on 4° Off-Axis 4H SiC with Addition of HCl
Authors: Zhang Jie , Mazzola Janice , Sunkari Swapna G. , Stewart Gray , Klein Paul B. , Ward Rachael M. , Glaser E.R. , Lew Kok Keong , Gaskill D. Kurt , Sankin Igor , Bondarenko Volodymyr , Null David , Sheridan David C. , Mazzola Michael S.
Published: March 2009

Epitaxial growth of 3-in, 4° off-axis 4H SiC with addition of HCl has been presented. Good surface morphology with a low defect density has been obtained, even for epi thickness of 38 µm. Comprehensive characterization techniques conducted on the epi material obtained in this process have independently confirmed the high purity and low density of crystalline imperfections. Low temperature PL displays clear free exciton I77 recombination while no L1 line is discernable. DLTS measurements have confirmed a low concentration of Z1/2 and EH6/7 below or in the range of 1011 cm-3. Time resolved PL at room temperature performed on a 38 µm thick epi wafer gives long carrier lifetime in the range of 1.5 to above 5 µsec. PiN diodes with diode area up to 25 mm2 have demonstrated blocking voltages above 900V, with a max electric field of above 2.5 MV/cm.
Degradation of Charge Collection Efficiency for 6H-SiC Diodes by Electron Irradiation
Authors: Iwamoto Naoya , Onoda Shinobu , Hishiki Shigeomi , Ohshima Takeshi , Murakami Makoto , Nakano I. , Kawano K.
Published: March 2009

6H-SiC n+p diodes fabricated on a p-type epitaxial layer were irradiated with
1MeV-electrons at fluences up to 6×1016 cm-2 to clarify their radiation tolerance. Charge Collection
Efficiencies (CCEs) were evaluated from the Transient Ion Beam Induced Current (TIBIC) using
Oxygen (O) ions. The CCE of 93 % was obtained for non-electron-irradiated diodes, and no
significant change in CCE was observed for diodes irradiated with electrons at fluences below 1×1015
cm-2. The degradation of CCE was observed after irradiation at fluences above 5×1015 cm-2.
High-Temperature Operation of 50 A (1600 A/cm2), 600 V 4H-SiC Vertical-Channel JFETs for High-Power Applications
Authors: Cheng Lin , Sankin Igor , Bondarenko Volodymyr , Mazzola Michael S. , Scofield James D. , Sheridan David C. , Martin P. , Casady Janna R. B. , Casady Jeff B.
Published: March 2009

In this work we have demonstrated the high-temperature operations of 600 V/50 A 4HSiC
vertical-channel junction field-effect transistors (VJFETs) with an active area of 3 mm2.
Specific-on resistance (RONSP) in the linear region of a single die is less than 2.6 mW.cm2 while the
drain-source current is over 50 A under a gate bias (VGS) of 3 V. A reverse blocking gain of 54 is
obtained at gate bias ranging from -13 V to -23 V and drain-source leakage current (IRDS) of 200 μA.
To demonstrate the use of SiC VJFETs for high-power applications, eight 3 mm2 SiC VJFETs are
bonded in a high current 600-V module. RONSP in the linear region of these eight-paralleled SiC
VJFETs is 2.8 mW.cm2 at room temperature and increased to 5.35 mW.cm2 at an ambient
temperature of 175 °C in air, corresponding to a shift of 0.61%/°C from room temperature to 175 °C.
Meanwhile, the forward current is over 360 A at room temperature and reduces to 188 A at 175 °C
at drain-source bias (VDS) of 5.25 V and VGS of 3 V.
Homoepitaxial Growth of 4H-SiC on On-Axis Si-Face Substrates Using Chloride-Based CVD
Authors: Leone Stefano , Pedersen Henrik , Henry Anne , Kordina Olof , Janzén Erik
Published: March 2009

The homoepitaxial chloride-based CVD growth is demonstrated on Si-face on-axis 4H-SiC substrates. The use of chloride-based CVD has allowed growth of 100% 4H-SiC epitaxial layers with a growth rate of 20µm/h, thus about seven times higher than with standard precursors. It was also found that chlorine etches preferentially the 3C-SiC inclusions that tends to nucleate on Si-face on-axis substrates. Therefore the Cl/Si ratio is a fundamental process parameter to optimize.
Fabrication and Testing of 6H-SiC JFETs for Prolonged 500 °C Operation in Air Ambient
Authors: Spry David J. , Neudeck Philip G. , Chen Liang Yu , Beheim Glenn M. , Okojie Robert S. , Chang Carl W. , Meredith Roger D. , Ferrier Terry L. , Evans Laura J.
Published: March 2009

This paper reports on the fabrication and testing of 6H-SiC junction field effect transistors
(JFETs) and a simple differential amplifier integrated circuit that have demonstrated 2000 hours of
electrical operation at 500 °C without degradation. The high-temperature ohmic contacts, dielectric
passivation, and packaging technology that enabled such 500 °C durability are briefly described. Key
JFET parameters of threshold voltage, on-state resistance, transconductance, and on-state current, as
well as the gain of the differential amplifier integrated circuit, exhibited less than 7% change over the
first 2000 hours of 500 °C operational testing.
SiC Lateral Trench JFET for Harsh-Environment Wireless Systems
Authors: Sankin Igor , Bondarenko Volodymyr , Sheridan David C. , Mazzola Michael S. , Casady Jeff B. , Fraley John , Schupbach Marcelo
Published: March 2009

SiC Lateral Trench JFET (LTJFET) technology is demonstrated as a promising candidate
for use in high-temperature wireless telemetry systems. 4H-SiC LTJFETs were designed, fabricated
and characterized for DC, and small-signal AC and RF performance at different case temperatures.
Four-fold drain current reduction was observed at 460°C as compared to RT measurements. The
measured threshold voltage shift was less than 2.3 mV/°C from 21°C to 460°C. A simple common
source amplifier built using a fabricated device demonstrated stable small-signal AC performance
after 100 hrs of operation at 450°C. Small-signal RF measurements were carried out on the packaged
devices at different temperatures. GMax above 8 dB was measured over the L-band frequency range
at RT. The average degradation of small-signal power gain measured at f=250 MHz did not exceed
0.0125 dB/ °C over the temperature ranging from 21°C to 365°C.
Development of High Temperature Lateral HV and LV JFETs in 4H-SiC
Authors: Zhang Y. , Sheng Kuang , Su Ming , Zhao Jian Hui , Alexandrov Peter , Fursin Leonid
Published: March 2009

A series of high voltage (HV) and low voltage (LV) lateral JFETs are successfully
developed in 4H-SiC based on the vertical channel LJFET (VC-LJFET) device platform.
Both room temperature and 300 oC characterizations are presented. The HV JFET shows a
specific-on resistance of 12.8 mΩ·cm2 and is capable of conducting current larger than 3 A at
room temperature. A threshold voltage drop of about 0.5 V for HV and LV JFETs is observed
when temperature varies from room temperature to 300 oC. The measured increase of
specific-on resistance with temperature due to a reduction of electron mobility agrees with
the numerical prediction. The first demonstration of SiC power integrated circuits (PIC) is
also reported, which shows 5 MHz switching at VDS of 200 V and on-state current of 0.4 A.
Fast Switching Characteristics of 4H-SiC RESURF-Type JFET
Authors: Fujikawa Kazuhiro , Sawada Kenichi , Tsuno Takashi , Tamaso Hideto , Harada Shin , Namikawa Yasuo
Published: March 2009

400V/2.5A 4H-SiC JFETs having a reduced surface field (RESURF) structure were
fabricated. Measurements on the static and switching characteristics were carried out. The
on-resistance was 0.86 W. The turn-on time (ton) and the turn-off time (toff) were 8ns and 10 ns,
respectively. The fabricated JFETs showed low on-resistance and fast switching characteristics.
4H-SiC RESURF-type JFETs, which is a sort of lateral transistor, are preferable to a module
configuration of switching devices. Moreover, they are promising for application to DC power
supplies with higher efficiency and smaller size owing to their low on-resistance and fast switching
characteristics.
6H-SiC Lateral JFETs for Analog Integrated Circuits
Authors: Fu Xiao An , Patil Amita , Neudeck Philip G. , Beheim Glenn M. , Garverick Steven , Mehregany Mehran
Published: March 2009

This paper reports fabrication and electrical characterization of 6H-SiC n-channel,
depletion-mode, junction-field-effect transistors (JFETs) for use in high-temperature analog
integrated circuits for sensing and control in propulsion, power systems, and geothermal exploration.
Electrical characteristics of the resulting JFET devices have been measured across the wafer as a
function of temperature, from room temperature to 450oC. The results indicate that the JFETs are
suitable for high-gain amplifiers in high-temperature sensor signal processing circuits.
Investigations on Polytype Stability and Dislocation Formation in 4H-SiC Grown by PVT
Authors: Schmitt Erwin , Straubinger Thomas L. , Rasp Michael , Vogel Michael , Wohlfart Andreas
Published: March 2009

We carried out investigations to elucidate the reasons for polytype changes in 4H. The aim was to sustain polytype stability throughout the entire process. The investigations were accompanied by studies on the formation of basal plane dislocations and their role as source for stacking faults. Several methods for the evaluation of material properties were applied to determine quality most precisely, e.g. KOH-defect-etching, optical microscopy, electron microscopy and X-ray-diffraction. We found out that several influences in growth conditions have to be controlled in a proper manner to achieve defect reduction. Based on these investigations we were able to improve our process and the crystal quality significantly. Best values for 3” 4H wafers show that EPD = 5x103 cm-2 , MPD < 0.1 cm-2 and FWHM-values < 15 arcsec can be achieved.
Influence of Passivation Oxide Properties on SiC Field-Plated Buried Gate MESFETs
Authors: Nilsson Per Åke , Sudow Mattias , Allerstam Fredrik , Andersson Kristoffer , Sveinbjörnsson E.Ö. , Hjelmgren Hans , Rorsman Niklas
Published: March 2009

Silicon Carbide MESFETs for microwave frequencies were made using a field-plated
buried gate approach. The devices were fabricated using passivation oxides with different interface
trap densities. By using a passivation oxide with a reduced interface trap density, grown in a sodium
containing ambient, it was possible to achieve a very high continous wave output power density of the
device: 8 W/mm at 3 GHz and 1 dB compression.
Measurement of Local Temperatures Using µ-Raman of SiC and AlGaN-GaN/SiC Power and RF Devices
Authors: Glembocki Orest J. , Caldwell Joshua D. , Mittereder Jeffrey A. , Calame Jeffrey P. , Binari Steven C. , Stahlbush Robert E.
Published: March 2009

Confocal μ-Raman was used to measure the operating temperatures in SiC MESFETS,
AlGaN/GaN/SiC HEMT’s and 4H-SiC PiN diodes. Temperatures obtained from thermal imaging of
the MESFETS compared well with those measured from Raman scattering. Operating temperatures
were also obtained for large area PiN diode and it was shown that a single point at the center of the
device can be used to measure the average temperature.
Simulation and Modeling of Thermal Effects in 4H-SiC NPN BJTs
Authors: Huang Chih Fang , Tseng Chien Yuen
Published: March 2009

This paper presents a simulation study on the thermal effects in 4H-SiC NPN BJTs.
Simulation results show several important effects on the BJT characteristics such as base contact
locations, current gain reduction due to high level injection in the base at high current densities, and
the non-uniform current distribution due to long fingers and poor contact resistance. A DC spice
model with temperature effects is created. The IVs of the model are in good agreement with
measurement.
Reliability Testing of 4H-SiC Bipolar Junction Transistors in Continuous Switching Applications
Authors: Kaplan Steven L. , Ogunniyi Aderinto
Published: March 2009

Continued improvement in silicon carbide (SiC) material processing has allowed
development of efficient high temperature devices which are uniquely suited to power electronics
circuit designs. The 4H-SiC structure has several intrinsic characteristics that facilitate optimal
speed and power handling during high temperature device operation. These characteristics include
wide bandgap (3.2 eV), high dielectric breakdown (3.5 MV/cm), and high thermal conductivity (4.9
W/cm-K)[1,2]. By combining these properties, SiC bipolar junction transistors (BJTs) can achieve
fast, low impedance switching at high voltages (1.2 kV). New generation devices are being
developed with increased current handling capability, as well as improved forward voltage
characteristics. The device considered here, along with its on-state DC characteristic, is shown in
figure 1. The BJTs are approximately 5mm by 5mm, and are nominally rated for a maximum Ice of
50A. Measurements on the Tektronix 371B curve-tracer indicate current gains over 60 at 25 oC and
roughly 40 at 150 oC. These results were obtained at collector currents up to 20A. The base current
for BJTs is typically 300 to 800 mA, depending on device temperature and the maximum device
current required. In order to meet current handling requirements of up to 80A, as required for power
conversion in modern military systems such as the hybrid-electric vehicle (HEV), it is necessary to
configure these devices in parallel with minimal external cooling. The resulting switching circuits
must therefore be validated for operation at high temperatures (package temperatures of 90 oC, and
junction temperatures to 150 oC). Validation includes characterization of the devices in clamped
inductive circuits with devices configured both alone and in parallel over time. Figure 4 shows
measurement waveforms obtained during continuous clamped inductive switching. The primary
focus of this work is to establish the overall performance and reliability of these newer generation
SiC BJTs in power conversion circuits. Failure analysis and critical performance issues, such as
current sharing, energy loss, and total reverse recovery charge are addressed. The initial results of
the experiments indicate that these SiC switches have the potential to perform reliably in high
temperature power conversion.
Development of a Practical High-Rate CVD System
Authors: Ishida Yuuki , Takahashi Tetsuo , Okumura Hajime , Arai Kazuo , Yoshida Sadafumi
Published: March 2009

We have developed a new chemical vapor deposition (CVD) system that is capable of a high growth rate of over 100 µm/h with good uniformities of thickness and carrier concentration. In this CVD system, the process gases contribute efficiently to epitaxial growth. In a demonstration of the abilities of the CVD system, we achieved an average growth rate of 140 µm/h, a thickness uniformity of 3.9%, and a carrier concentration uniformity of 8.9% in a 2-inch wafer, without degradation of the crystallinity.
Design, Simulation, and Characterization of High-Voltage SiC p-IGBTs
Authors: Sui Yang , Cooper James A. , Wang X. , Walden Ginger G.
Published: March 2009

We have designed, simulated, fabricated, and characterized high-voltage 4H-SiC p-channel
DMOS-IGBTs on 20 kV blocking layers for use as the next generation of power switching devices.
These p-IGBTs exhibit significant conductivity modulation in the drift layer. The maximum currents
of the experimental p-channel IGBTs are 1.2x and 2.1x higher than the ideal 20 kV n-channel
DMOSFETs at room temperature and 175°C, respectively.
Observation of Luminescence from Defects in 4H-SiC APDs Operating in Avalanche Breakdown
Authors: Soloviev Stanislav I. , Sandvik Peter M. , Vertiatchikh Alexey , Dovidenko K. , Cha Ho Young
Published: March 2009

In this work, we observed and investigated electro-luminescence (EL) from defects in
4H-SiC avalanche photodiodes. The EL irradiance originated from parallel lines oriented along
the [11-20] crystallographic direction. Optical microscopy imaging was employed to analyze the
intensity distribution of luminescencing lines at different current densities. Electron beam
induced current (EBIC) methodology was employed to find correlation between the
luminescencing defects and dislocations in the epi-layers. TEM analysis of the substrate region
having the brightest luminescencing line was performed. There were a few defects at the depth of
about 3 μm from the sample surface where EL intensity had the highest value.