Electrical resistivity negative temperature

Resistivity. The temperature coefficient of electrical resistivity of commercial siUcon carbide at room temperature is negative. No data are given for refractory materials because resistivity is gready induenced by the manufacturing method and the amount and type of bond. Manufacturers should be consulted for specific product information. 

In the case of TES, the joule heating of the superconducting film produces a negative thermal feedback which increases the thermal stability. The thermal equilibrium takes place when joule heating is balanced by the thermal leak to the substrate. If for some reason in a TES, biased by a voltage V at the centre of the transition, the temperature decreases, an increase of the TES electrical resistance R takes place. Consequently, the bias power V2/R increases, bringing back the TES at the centre of the transition. 

A second historical line which, is of paramount importance to the present understanding of solid state processes is concerned with electronic particles (defects) rather than with atomic particles (defects). Let us therefore sketch briefly the, history of semiconductors [see H. J, Welker (1979)]. Although, the term semiconductor was coined in 1911 [J. KOnigsberger, J, Weiss (1911)], the thermoelectric effect had already been discovered almost one century earlier [T. J. Seebeck (1822)], It was found that PbS and ZnSb exhibited temperature-dependent thermopowers, and from todays state of knowledge use had been made of n-type and p-type semiconductors. Faraday and Hittorf found negative temperature coefficients for the electrical conductivities of AgzS and Se. In 1873, the decrease in the resistance of Se when irradiated by visible light was reported [W. Smith (1873) L. Sale (1873)]. It was also... 

The electrical resistivity data on crystals of indium(III) oxyfluoride indicate a nearly temperature independent conductor (3.6 X 10 2 fl-cm. at room temperature and 1.8 X 10-2 fl-cm. at liquid-helium temperature) with high negative thermoelectric power (—230 juV./°C.). These properties are similar to those observed for some conductive forms of indium(III) oxide. 

The thermisters (TMs) are semiconductor device with a high resistance dependence on temperature. They may be calibrated as a thermometer. The semiconductor sensor exhibits a large change in resistance that is proportional to a small change in temperature. Normally TMs have negative thermal coefficients. Like RTDs, they operate on the principle that the electrical resistance of a conductive metal is driven by changes in temperatures. Variations in the conductor s electrical resistance are thus interpreted and quantified, as changes in temperature occur. 

Metals and semiconductors have positive and negative slopes in their electrical resistivity p) vs. temperature (T) curves as schematically shown in (109) and (110), respectively. By definition, the Fermi surface disappears when a band gap opens at the Fermi level. If the Fermi surface nesting is complete, all the Fermi surface is removed by the appropriate orbital mixing. However, if the Fermi surface nesting is incomplete, only the nested portion of the surface is removed by orbital mixing. The unnested portion is left as small Fermi surface pockets. The system will thus retain its metallic properties although the number of carriers (i.e. those electrons at the Fermi level) will be... 

The most frequently used source of infrared light for infrared spectrometers is so called the Nemst stick. This stick is about two to four centimeters long and one to three millimeters thick, and is made from zirconium oxide with additions of yttrium oxide and oxides of other metals. This mixture of oxides has a negative temperature coefficient of electrical resistance. This means that its electrical conductivity increases with an increase in temperature. At room temperature, the Nemst stick is a non-conductor. Thus, an auxiliary heating is necessary for ignition of the Nernst stick. Even if the Nernst stick is red-hot, it can be heated further by electricity. The normal operating temperature of this infrared light source is approximately 1900 K. 

The electrical resistivity, which has a negative temperature coefficient, reaches... 

Thermistors are usually made from ceramic metal oxide semiconductors, which have a large negative temperature coefficient of electrical resistance. Thermistor is a contraction of thermal-sensitive-resistor. The recommended temperature range of operation is from -55 to 300°C. The popularity of this device has grown rapidly in recent years. Special thermistors for cryogenic applications are also available [12]. 

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