Temperature-dependent resistance

Thermistors are temperature-dependent resistances, normally constructed from metal oxides. The resistance change with temperature is high compared with the metallic resistances, and is usually negative the resistance decreases with temperature increase. The temperature characteristics are highly nonlinear. Such thermistors, having a negative temperature coefficient, are called NTC thermistors. Some thermistors have a positive temperature coefficient (PTC), but they are not in common use for temperature measurement. 

Temperature-dependent resistivity data (In p vs 1/T) for both Eu3lnP3 and Eu3ln2P4 are shown in Pig. 11.3 and indicate that they are semiconductors. The room-temperature resistivities are on the order of 1-100 cm. Band gaps were determined by fitting the data from about 130-300 K to the relationship. In p= Eg/ Ik T + f, providing a band gap. Eg, of approximately 0.5 eV for both samples. Since these two compounds can be rationalized as electron-precise Zintl phases, semiconducting behavior is expected. 

The second study of possible relevance reported that PbSe, precipitated from selenosulphate solution (not in the form of a film), was found to have an (electrical) bandgap, measured by temperature-dependent resistivity, of 0.4 eV [48], In the same study, samples prepared by reaction of solid lead tartrate with H2Se exhibited an electrical bandgap of 0.92 eV. These results suggest the occurrence of size quantization. 

The lower carrier density of the 80-nm nanowires compared to bulk bismuth is due to the smaller band overlap in the former. For the 40-nm bismuth nanowires, the carrier density has a temperature dependence similar to bulk bismuth at high temperatures, but it drops rapidly with decreasing temperature at low temperatures. Because the carrier density is highly dependent on wire diameter, the transport properties of bismuth nanowires are expected to be highly sensitive to wire diameter, as will be shown experimentally in the section temperature-dependent resistivity of nanowires. ... 

Transport properties (continued.) semiclassical model, 192-193 temperature-dependent resistivity of nanowires, 193-198 Triplet sites on supports, 63-64 Tungsten species, SiC>2-supported, 63 Turnover numbers (TON), nanostructured materials, 6... 

Figure 20 displays the superconducting transition of (TMTSF)2PF6 salts observed by resistivity data [6,9]. What is remarkable in Fig. 20 is the strong temperature dependence of p(7) above Tc, unlike the behavior of regular metals, for which the resistivity is limited at low temperature by temperature-independent elastic scattering. The behavior of the temperature dependent resistivity at low temperature in TM2X compounds has been ascribed to a precursor effect above Tc [6]. 

Because of the softness of organic metals one expects them to show interesting behavior under applied pressures. This had been demonstrated earlier by Jerome and co-workers on several compounds and in the case of TMTSF-DMTCNQ (DMTCNQ = dimethyltetracyanoqui-nodimethane) a pressure of 10 kbar transforms it abruptly from a Peierls semiconductor with Tm = 50 K to a metal at all temperatures (91). When the temperature-dependent resistance of the (TMTSF)2X family became known, the very low transition temperatures in some of the compounds suggested that these salts would easily become metallic, and maybe even superconducting, under pressure. 

In contrast to this observation, later results [334] did not show any signs of hysteresis in the temperature-dependent resistivity. 

A variety of enzyme-based biosensors have been tested using thermistors as the means of signal transduction. Thermistors are similar to electrical resistors, but possess highly temperature dependent resistance values. Since many enzymatic... 

Figure 4. Temperature-dependent resistance for a crystal from a Pt crucible run.

The temperature-dependent resistivities of the four materials we have... 

FIGURE 8 (a) Temperature-dependent resistivities of sate organic conductors. 

Figure 9. Temperature-dependent resistance of thick film simple oxides and Fe203-Sn02 composites in air, RH 30%.

Fig. 66. Physical properties of lAufAg Au.rSn/re.il 1. (a) Temperature dependence of the magnetic susceptibility y (b) temperature-dependent resistivity p (c) optical diffuse reflectance R versus wavelength A of incident light. (From Fig. 4 in Dhingra, S. S. Seo, D.-K. Kowach, G. R. Kremer, R. K. Shreeve-Keyer, J. L. Haushalter, R. C. Whangbo, M.-H. Angew. Chern., Int. Ed. Engl. 1997, 36, 1087.)...

Fig. 66. Physical properties of [AuCAgi-jAujljSnzTeJ. (a) Temperature dependence of the magnetic susceptibility x, (b) temperature-dependent resistivity p (c) optical diffuse reflectance R versus wavelength A of incident light. (From Fig. 4 in Dhingra,...

---