A scanning electron microscope study of defects in PTC materials

1988 ◽  
Vol 46 ◽  
pp. 942-943
Author(s):  
James W. Smith
Keyword(s):  
Positive Temperature Coefficient ◽  
Inrush Current ◽  
Positive Temperature ◽  
Scanning Electron Microscope Study ◽  
Limited Temperature ◽  
Limited Temperature Range ◽  
Ideal Tool ◽  
Increasing Temperature ◽  
Solid Form ◽  
Voltage Breakdown

BaTiO3 and its solid solutions with PbTiO3 and SrTiO3 are normally insulators but, when doped with small amounts of trivalent ions, they become semiconducting. Materials in this family also possess a positive temperature coefficient of resistance (an increase in resistance with increasing temperature) over a limited temperature range and are often referred to as PTCs. The temperature where the PTC region begins is determined by the Ba/Pb/Sr ratio.The materials are generally prepared by solid state reaction of a mixture of oxides and carbonates which is subsequently sintered into a solid form. The electrical properties of such a body, in particular properties such as inrush current capability and voltage breakdown, are critically affected by microdefects in the materials which often originate during processing. The SEM is an ideal tool for studying such defects since they generally manifest themselves as localized variations in resistance.

Temperature Dependence of Hole Impact Ionization Coefficient in 4H-SiC Photodiodes

2009 ◽  
Vol 615-617 ◽  
pp. 311-314 ◽  
Author(s):  
W.S. Loh ◽  
J.P.R. David ◽  
B.K. Ng ◽  
Stanislav I. Soloviev ◽  
Peter M. Sandvik ◽  
...  
Keyword(s):  
Phonon Scattering ◽  
Impact Ionization ◽  
Positive Temperature Coefficient ◽  
Positive Temperature ◽  
Different Temperatures ◽  
Ionization Coefficients ◽  
Increasing Temperature ◽  
The Impact ◽  
Good Agreement ◽  
Ionization Rates

Hole initiated multiplication characteristics of 4H-SiC Separate Absorption and Multiplication Avalanche Photodiodes (SAM-APDs) with a n- multiplication layer of 2.7 µm were obtained using 325nm excitation at temperatures ranging from 300 to 450K. The breakdown voltages increased by 200mV/K over the investigated temperature range, which indicates a positive temperature coefficient. Local ionization coefficients, including the extracted temperature dependencies, were derived in the form of the Chynoweth expression and were used to predict the hole multiplication characteristics at different temperatures. Good agreement was obtained between the measured and the modeled multiplication using these ionization coefficients. The impact ionization coefficients decreased with increasing temperature, corresponding to an increase in breakdown voltage. This result agrees well with the multiplication characteristics and can be attributed to phonon scattering enhanced carrier cooling which has suppressed the ionization process at high temperatures. Hence, a much higher electric field is required to achieve the same ionization rates.

scholarly journals Beating Thermal Deterioration of Magnetization with Mn4C and Exchange Bias in Mn–C Nanoparticles

Nanomaterials ◽  
2018 ◽  
Vol 8 (12) ◽  
pp. 1056 ◽  
Author(s):  
Ping-Zhan Si ◽  
Xin-You Wang ◽  
Hong-Liang Ge ◽  
Hui-Dong Qian ◽  
Jihoon Park ◽  
...  
Keyword(s):  
Temperature Coefficient ◽  
Exchange Bias ◽  
Arc Discharge ◽  
Magnetic Ordering ◽  
Positive Temperature Coefficient ◽  
Positive Temperature ◽  
Thermal Deterioration ◽  
Increasing Temperature ◽  
P Type ◽  
Discharge Method

The magnetization of most materials decreases with increasing temperature due to thermal deterioration of magnetic ordering. Here, we show that Mn4C phase can compensate the magnetization loss due to thermal agitation. The Mn–C nanoparticles containing ferrimagnetic Mn4C and other Mn–C/Mn-O phases were prepared by using the traditional arc-discharge method. A positive temperature coefficient of magnetization (~0.0026 Am2 kg−1 K−1) and an exchange bias up to 0.05 T were observed in the samples. We ascribe the exchange bias to the co-existence of ferrimagnetic Mn4C/Mn3O4 and antiferromagnetic α-Mn(C)/MnO phases. The positive temperature coefficient of magnetization of the samples was ascribed to the presence of Mn4C phase, which is considered as a Néel’s P-type ferrimagnet.

The Temperature Dependent Breakdown Voltage For 4H- and 6H-SiC Diodes

2000 ◽  
Vol 622 ◽  
Author(s):  
Y. S. Lee ◽  
M. K. Han ◽  
Y. I. Choi
Keyword(s):  
High Temperature ◽  
Temperature Coefficient ◽  
Breakdown Voltage ◽  
Impact Ionization ◽  
Positive Temperature Coefficient ◽  
Positive Temperature ◽  
Ionization Coefficient ◽  
Temperature Dependent ◽  
Increasing Temperature ◽  
Temperature Applications

ABSTRACTThe breakdown voltages of 6H- and 4H-SiC rectifiers as function of temperature were modeled analytically in both non-reachthrough diode and reachthrough diode. The breakdown voltage was derived by the ionization integral employing accurate hole impact ionization coefficient. The breakdown voltage of SiC rectifiers was increased with increasing temperature and the positive temperature coefficient of breakdown voltage indicates that SiC rectifiers are suitable for high temperature applications. The breakdown voltages of both 6H- and 4H-SiC diodes were increased by M(T)-1/4 in NRDs and M(T)-1/8 in RDs.

Positive Temperature Coefficient of Resistance in MOCVD (Ba0.75Sr0.25)Ti1+yO3+z Films

2002 ◽  
Vol 748 ◽  
Author(s):  
S. Saha ◽  
D. Y. Kaufman ◽  
S. K. Streiffer ◽  
R. A. Erck ◽  
O. Auciello
Keyword(s):  
Temperature Coefficient ◽  
Weak Field ◽  
Positive Temperature Coefficient ◽  
Positive Temperature ◽  
Temperature Coefficient Of Resistance ◽  
Current Voltage ◽  
Ptcr Effect ◽  
Bst Films ◽  
Current Voltage Characteristics ◽  
Increasing Temperature

ABSTRACTThe leakage and dielectric properties of a thickness series (90–480 nm) of {100} fiber-textured MOCVD (Ba0.75Sr0.25)Ti1+yO3+z (BST) thin films on Pt/SiO2/Si were investigated. The temperature and voltage dependence of the permittivity were consistent with previous observations, where thinner films demonstrated a suppressed temperature and electric field response that transitioned to a more bulk-like response with increasing film thickness. The current-voltage characteristics showed two distinct regimes. At low fields the current displayed weak field dependence and a monotonic increase with increasing temperature. In contrast, positive temperature coefficient of resistance (PTCR) was observed in the high-field leakage current behavior. The PTCR behavior was more pronounced for thicker BST films. Factors contributing to the observed PTCR effect are outlined and contrasted with the description for bulk BaTiO3 ceramics.

Pb-FREE SOLDERS: ESTIMATING OF SOME PHYSICOCHEMICAL AND THERMODYNAMIC PROPERTIES OF TERNARY Cu-Ag-In SYSTEM

2019 ◽  
Vol 26 (10) ◽  
pp. 1950076 ◽  
Author(s):  
SALMA BELMOUJOUD ◽  
RACHIDA M’CHAAR ◽  
ABDELAZIZ SABBAR
Keyword(s):  
Surface Tension ◽  
Cross Sections ◽  
Theoretical Models ◽  
Enthalpy Of Mixing ◽  
Positive Temperature Coefficient ◽  
Ternary Alloys ◽  
Positive Temperature ◽  
Geometric Models ◽  
Different Temperatures ◽  
Increasing Temperature

The surface tension and viscosity in the liquid Cu-Ag-In ternary alloys have been estimated using Muggianu and Toop geometric models and Seetharaman–Sichen equations, respectively along a cross-section of [Formula: see text]/[Formula: see text], 1/1 and 2/1. The surface tension has also been estimated using Butler equation. In addition, the enthalpies of the same ternary alloys have been predicted at different temperatures along five cross-sections [Formula: see text]/[Formula: see text], 1/2, 1/1, 2/1 and 3/1 using Kohler, Toop and Chou models. The geometric models are used in this work in order to verify their effectiveness since they are considered as the most widespread theoretical models used for metallic alloys. The estimated values obtained show that the surface tension decreases with increasing temperature for the all studied models and equations and increase with increasing copper-composition, except for few Cu-compositions where an opposite tendency is observed. It should be noted that the surface tension has a negative and positive temperature coefficient (d[Formula: see text]/d[Formula: see text]. The viscosity decreases with increasing temperature but increases with increasing copper-compositions. The calculated surface tension and enthalpy of mixing of the investigated system are compared with the reachable experimental data and a relatively excellent accord was obtained.

KANTHAL 70

Alloy Digest ◽  
1981 ◽  
Vol 30 (9) ◽  
Keyword(s):  
Operating Temperature ◽  
Heat Treating ◽  
Positive Temperature Coefficient ◽  
Pure Nickel ◽  
Voltage Source ◽  
Voltage Regulator ◽  
Positive Temperature ◽  
Automotive Applications ◽  
Resistance Thermometers ◽  
In Series

Abstract KANTHAL 70 alloy was designed to provide a high positive temperature coefficient to electrical resistance comparable with that of pure nickel; however, it has much higher electrical resistivity than pure nickel. This makes it useful as a voltage regulator when placed in series with another electrical device across a fluctuating voltage source. Kanthal 70 has a maximum recommended operating temperature of 600 C and is used widely in resistance thermometers and in various appliance and automotive applications. This datasheet provides information on composition, physical properties, and tensile properties. It also includes information on corrosion resistance as well as forming, heat treating, and joining. Filing Code: Ni-270. Producer or source: The Kanthal Corporation.

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