Electrical resistivity temperature dependence

Fig. 4. Schematic longitudinal electrical resistivity temperature dependence for quasi- 1-D RIS. 

She] Electrical resistivity-temperature dependence measurements Electrical resistivity... 

Temperature The level of the temperature measurement (4 K, 20 K, 77 K, or higher) is the first issue to be considered. The second issue is the range needed (e.g., a few degrees around 90 K or 1 to 400 K). If the temperature level is that of air separation or liquefact-ing of natural gas (LNG), then the favorite choice is the platinum resistance thermometer (PRT). Platinum, as with all pure metals, has an electrical resistance that goes to zero as the absolute temperature decreases to zero. Accordingly, the lower useful limit of platinum is about 20 K, or liquid hydrogen temperatures. Below 20 K, semiconductor thermometers (germanium-, carbon-, or silicon-based) are preferred. Semiconductors have just the opposite resistance-temperature dependence of metals—their resistance increases as the temperature is lowered, as fewer valence electrons can be promoted into the conduction band at lower temperatures. Thus, semiconductors are usually chosen for temperatures from about 1 to 20 K. 

The specific electrical resistances usually depend on the material and the temperature [31]. For the most important pipe materials these are (in 10 Q cm) ... 

It should be remarked, however, that the specific resistance of polymers cannot uniquely be defined the electric resistance strongly depends on the electric tension applied (Ohm s law is not obeyed), and also on the time of application of the tension. Moreover, the resistance depends on temperature it decreases drastically upon... 

The thermal conductivity detector (TCD) is based on changes in the thermal conductivity of the gas stream brought about by the presence of separated sample molecules. The detector elements are two electrically heated platinum wires, one in a chamber through which only the carrier gas flows (the reference detector cell), and the other in a chamber that takes the gas flow from the column (the sample detector cell). In the presence of a constant gas flow, the temperature of the wires (and therefore their electrical resistance) is dependent on the thermal conductivity of the gas. Analytes in the gas stream are detected by temperature-dependent changes in resistance based on the thermal conductivity of each separated molecule the size of the signal is directly related to concentration of the analyte. 

The electrical resistance of the membrane is an important property of ion-exchange membranes. The membrane resistance is determined by the lEC and the mobility of the ions within the membrane matrix. The electrical resistance is dependent on temperature and decreases with increasing temperature. 

From an optical viewpoint, on the other hand, the difference between semiconductors and insulators lies in the value of Eg. The admitted boundary is usually set at 3 eV (see Appendix A for the energy units) and materials with Eg below this value are categorized as semiconductors, but crystals considered as semiconductors like the wurtzite forms of silicon carbide and gallium nitride have band gaps larger than 3 eV, and this value is somewhat arbitrary. The translation into the electrical resistivity domain depends on the value of Eg, and also on the effective mass of the electrons and holes, and on their mobilities. The solution is not unique moreover, the boundary is not clearly defined. Semi-insulating silicon carbide 4H polytype samples with reported room temperature resistivities of the order of 1010flcm could constitute the... 

Vitl] Preparation from powders annealing at 400-490°C for 1500 h microstmcture analysis Vickers hardness electrical resistance. Concentration dependence of H and p temperature dependence of p partial isothermal section at 400°C in the vicinity of FeNi3 partial vertical section Fc3Ni-Co below 500°C. 

The electrical resistance pyrometer depends on the principle that the electrical resistance of a conductor changes with temperature the instrument is designed to measure these changes and is calibrated in... 

We show in Fig.l the typical temperature dependence of electrical resistivity for ZrSe2(3N-GL GH). The electrical resistivity almost depends on the relation of p = Po + AT. The n value is 2.0 for the L H-samples. We remark here that the magnitude of the resistivity for the H-sample is smaller than the one for the L-sample. A similar result was obtained also for the 2N-G-sample. This is ascribed to the difference of the carrier concentration, as shown in a later figure. This behavior of the resistivity was interpreted by Klipstein et al. on the basis of... 

Most textile sensors are based on the use of conductive materials. Indeed, the electrical resistance is dependent on other factors (Castano and Flatau, 2014) such as mechanical strain, temperature or humidity. When a mechanical strain is applied on conductive elements, the resulting change in electrical resistance is called piezoresistivity (Carmona et al., 1987) and can be estimated by deriving Ohm s law ... 

Recently, in some cases, it has been found ftiat the electrical anisotropy is very large (lO" ) [45,300,391]. Figure 3.17 shows the resistivity temperature dependence of T-(P-5,5-DMEDT-TTF)2(AuBr2)i(AuBr2)o.75 [261,383,391] in-crystal-plane and out-of-plane. The compound behaves as a 2D metal. Moreover, compounds with stoichiometry 1 1 [206,326,341a] or stoichiometry 1 1 [388b] were found to remain metallic down to low temperatures. 

Thermal Conductivity Detector One of the earliest gas chromatography detectors, which is still widely used, is based on the mobile phase s thermal conductivity (Figure 12.21). As the mobile phase exits the column, it passes over a tungsten-rhenium wire filament. The filament s electrical resistance depends on its temperature, which, in turn, depends on the thermal conductivity of the mobile phase. Because of its high thermal conductivity, helium is the mobile phase of choice when using a thermal conductivity detector (TCD). 

Plasma-deposited siUcon nitride contains large amounts of hydrogen, typically in the range of 20—25 atomic % H, and has polymer-like properties. The electrical resistivity of the film depends on the deposition temperature, the film stoichiometry, and the amounts of hydrogen and oxygen in the film. 

Nonferrous alloys account for only about 2 wt % of the total chromium used ia the United States. Nonetheless, some of these appHcations are unique and constitute a vital role for chromium. Eor example, ia high temperature materials, chromium ia amounts of 15—30 wt % confers corrosion and oxidation resistance on the nickel-base and cobalt-base superaHoys used ia jet engines the familiar electrical resistance heating elements are made of Ni-Cr alloy and a variety of Ee-Ni and Ni-based alloys used ia a diverse array of appHcations, especially for nuclear reactors, depend on chromium for oxidation and corrosion resistance. Evaporated, amorphous, thin-film resistors based on Ni-Cr with A1 additions have the advantageous property of a near-2ero temperature coefficient of resistance (58). 

The specific electrical resistance of concrete can be measured by the method described in Section 3.5. Its value depends on the water/cement value, the type of cement (blast furnace, portland cement), the cement content, additives (flue ash), additional materials (polymers), the moisture content, salt content (chloride), the temperature and the age of the concrete. Comparisons are only meaningful for the... 

Early transport measurements on individual multi-wall nanotubes [187] were carried out on nanotubes with too large an outer diameter to be sensitive to ID quantum effects. Furthermore, contributions from the inner constituent shells which may not make electrical contact with the current source complicate the interpretation of the transport results, and in some cases the measurements were not made at low enough temperatures to be sensitive to 1D effects. Early transport measurements on multiple ropes (arrays) of single-wall armchair carbon nanotubes [188], addressed general issues such as the temperature dependence of the resistivity of nanotube bundles, each containing many single-wall nanotubes with a distribution of diameters d/ and chiral angles 6. Their results confirmed the theoretical prediction that many of the individual nanotubes are metallic. 

Ebbesen[4] was the first to estimate a conductivity of the order of lO fim for the black core bulk material existing in two thirds of tubes and one third of nanoparticles. From this observation, it may naturally be inferred that the carbon arc deposit must contain material that is electrically conducting. An analysis of the temperature dependence of the zero-field resistivity of similar bulk materials[14,15] indicated that the absolute values of the conductivity were very sample dependent. 

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