Transference number measurements on pure and doped crystals show that the predominant defect in CaF2 crystals in the anti-Frenkel disorder type involving equal concentrations of negative ion vacancies and negative ion interstitials. The mobilities of the F— vacancy and F— interstitial have been determined by measuring the electrical conductivity of crystals doped with NaF and YF3. The activation energy for mobility of the vacancies varies from 20±1.5 kcal/mole at 200°C to 12±1 kcal/mole at 600°C. For the interstitials, the mobility in the range from 690 to 920°C is given by u=(1.34×107)T−1 exp[−(19±4)×103/T] cm2/sec volt.The number of anti-Frenkel defects in the pure crystal in the range from 640 to 920°C is given by n0=2.96×1025exp[−(16.3×103)/T] cm−3.
A procedure has been developed for the exact calculation of the efficiency of thermoelectric generators and cooling devices in which the parameters of the materials have arbitrary temperature dependence. High speed computer techniques are found necessary. Approximate methods are reviewed and their discussion extended. A number of examples are worked out by both the exact and approximate methods. Comparison of these results show that the approximate methods agree with the exact method to about 5% in the case of power generation and to about 15% in the case of the refrigeration coefficient of performance. However, in the case of the maximum heat pumping rate deviations as large as a factor of 2 are found.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.