scholarly journals Unconventional Transport Properties of Reduced Tungsten Oxide WO2.9

2020 ◽  
Vol 5 (4) ◽  
pp. 63
Author(s):  
Alexander Shengelaya ◽  
Fabio La Mattina ◽  
Kazimierz Conder
Keyword(s):  
Transport Properties ◽  
Positive Temperature Coefficient ◽  
Strong Increase ◽  
Positive Temperature ◽  
Superconducting Transition ◽  
Resistivity Measurements ◽  
Magnetization Data ◽  
Underdoped Cuprates ◽  
Superconducting Fluctuations ◽  
Small Clusters

The temperature and magnetic field dependence of resistivity in WO2.9 was investigated. The variation of resistivity with temperature displayed unusual features, such as a broad maximum around 230 K and a logarithmic increase of resistivity below 16 K. In the temperature range 16–230 K, we observed metallic-like behavior with a positive temperature coefficient. The combined analysis of resistivity and magnetoresistance (MR) data shows that these unusual transport properties of WO2.9 can be understood by considering the (bi)polaronic nature of charge carriers. In contrast to magnetization data, superconducting transition below Tc = 80 K was not detected in resistivity measurements, indicating that the superconductivity is localized in small regions that do not percolate. We found a strong increase in positive MR below 80 K. This effect is similar to that observed in underdoped cuprates, where the substantial increase of MR is attributed to superconducting fluctuations in small clusters. Therefore, the temperature dependence of MR indicates the presence of non-percolating superconducting clusters in WO2.9 below 80 K in agreement with magnetization data.

scholarly journals Resistivity-Temperature Behavior of Intrinsically Conducting Bis(3-methoxysalicylideniminato)nickel Polymer

Polymers ◽  
2020 ◽  
Vol 12 (12) ◽  
pp. 2925
Author(s):  
Evgenii Beletskii ◽  
Valentin Ershov ◽  
Stepan Danilov ◽  
Daniil Lukyanov ◽  
Elena Alekseeva ◽  
...  
Keyword(s):  
Conductive Polymer ◽  
Lithium Ion ◽  
Positive Temperature Coefficient ◽  
Positive Temperature ◽  
Electrically Conductive ◽  
Resistivity Measurements ◽  
Elemental Analyses ◽  
Li Ion ◽  
Conductive State

Materials with a positive temperature coefficient have many applications, including overcharge and over-temperature protection in lithium-ion (Li-ion) batteries. The thermoresistive properties of an electrically conductive polymer, based on a Ni(salen)-type backbone, known as polyNiMeOSalen, were evaluated by means of in situ resistivity measurements. It was found that the polymer was conductive at temperatures below 220 °C; however, the polymer increased in resistivity by three orders of magnitude upon reaching 250 °C. Thermogravimetric results combined with elemental analyses revealed that the switch from the insulation stage to the conductive stage resulted from thermally dedoping the polymer. Electrochemical studies demonstrated that a polymer retains its electroactivity when it is heated and can be recovered to a conductive state through oxidation via electrochemical doping in an electrolyte solution.

Structural, Magnetic and Electrical Transport Properties of Ternary Compound LaCo2Ge2

2013 ◽  
Vol 455 ◽  
pp. 148-153
Author(s):  
Han Yuan Liu ◽  
Li Fu ◽  
Yong Quan Guo
Keyword(s):  
Transport Properties ◽  
Temperature Coefficient ◽  
Ternary Compound ◽  
Electrical Transport ◽  
Elevated Temperatures ◽  
Positive Temperature Coefficient ◽  
Positive Temperature ◽  
Electrical Measurements ◽  
Electrical Transport Properties ◽  
Xrd Patterns

Ternary compound LaCo2Ge2 was synthesized and characterized by means of XRD, magnetic and electrical measurements. Rietveld structure refinements of powder XRD patterns confirm that LaCo2Ge2 compound crystallizes with a body-centered tetragonal structure of ThCr2Si2-type (space group I4/mmm) with the unit lattice parameters a=4.105(6) Å and c=10.264(7) Å. Nd, Co and Ge occupy 2a, 4d and 4e crystal positions, respectively. Magnetism measurements show that LaCo2Ge2 is nearly temperature-impendent Pauli paramagnetic down to 100 K, whereas orders diamagnetic at elevated temperatures. The (T) measurement showed that is 0.34625 and a positive temperature coefficient for LaCo2Ge2 is equal to 0.82178, indicating that LaCo2Ge2 exhibits typical semimetallic.

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.

scholarly journals Thermal Noise Decoupling of Micro-Newton Thrust Measured in a Torsion Balance

Symmetry ◽  
2021 ◽  
Vol 13 (8) ◽  
pp. 1357
Author(s):  
Linxiao Cong ◽  
Jianchao Mu ◽  
Qian Liu ◽  
Hao Wang ◽  
Linlin Wang ◽  
...  
Keyword(s):  
Thermal Noise ◽  
Rotation Axis ◽  
Electrostatic Force ◽  
Thermal Control ◽  
Positive Temperature Coefficient ◽  
Torsion Balance ◽  
Positive Temperature ◽  
Thermal Drift ◽  
Low Thrust ◽  
Z Domain

The space gravitational wave detection and drag free control requires the micro-thruster to have ultra-low thrust noise within 0.1 mHz–0.1 Hz, which brings a great challenge to calibration on the ground because it is impossible to shield any spurious couplings due to the asymmetry of torsion balance. Most thrusters dissipate heat during the test, making the rotation axis tilt and components undergo thermal drift, which is hysteretic and asymmetric for micro-Newton thrust measurement. With reference to LISA’s research and coming up with ideas inspired from proportional-integral-derivative (PID) control and multi-timescale (MTS), this paper proposes to expand the state space of temperature to be applied on the thrust prediction based on fine tree regression (FTR) and to subtract the thermal noise filtered by transfer function fitted with z-domain vector fitting (ZDVF). The results show that thrust variation of diurnal asymmetry in temperature is decoupled from 24 μN/Hz1/2 to 4.9 μN/Hz1/2 at 0.11 mHz. Additionally, 1 μN square wave modulation of electrostatic force is extracted from the ambiguous thermal drift background of positive temperature coefficient (PTC) heater. The PID-FTR validation is performed with experimental data in thermal noise decoupling, which can guide the design of thermal control and be extended to other physical quantities for noise decoupling.

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.

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