The absolute Seebeck coefficient, electrical resistivity, and thermal resistivity were simultaneously measured on pure bismuth single crystals of various orientations between approximately 80° and 300°K. Using an overlapping two-band many-valley model, numerical values for the temperature dependence and anisotropy (where appropriate) of the following parameters have been calculated: (1) the overlap energy and the Fermi energy of the electrons and of the holes, (2) the density of states effective mass of the electrons and of the holes, (3) the separate electronic and lattice thermal conductivities, (4) the actual index of thermo-electric efficiency, and (5) the hypothetical ``optimum'' index of thermoelectric efficiency. The calculated electronic thermal conductivity includes a new term due to bipolar diffusion.

Compositions in the system Th02-Y01 6 were coprecipitated as oxalates and converted to oxides. Disks were pressed and sintered in oxygen at 1400" to 2200°C. Densities of the sintered disks were 96 to 98% of theoretical. Solid solutions with the fluorite-type structure were formed up to 20 to 25 mole yo YOl,s at 1400OC and up to 45 to 50 mole ' % Y O 1 .~ at 2200°C. Density data showed that these solid solutions correspond to Thl-,Y,Oz-o.s,, having a complete cation sublattice filled by T h 4 + and Y3+ ions, and vacancies in t h e anion sublattice. The observed increase in electrical conductivity with increase in Y01.5 content is consistent with charge transport by oxygen ions through a vacancy mechanism. Approximately 7 mole % T h o 2 is soluble in Y01.5 at 2200°C. Density results indicate an anion interstitial structure for the Yz03 phase. Transference number measurements indicate that the electrical conductivities are only partly due to ions.

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When a constant electric field is applied to a dielectric, the current density per unit field decreases with time from an ``initial conductivity'' to a ``final (or steady-state) conductivity.'' A study is made of this time-dependent polarization effect for ``pure'' NaCl crystals in the range from 50° to 200°C. The validity of Ohm's law and the superposition principle is demonstrated for these crystals; this establishes the linearity of the formal equation which relates polarization, electric field, and their time derivatives. Also studied are the effect of prolonged current flow, the effect of deliberate introduction of an air gap between the crystal and one of its electrodes, and the effects of impurities, deformation, x-ray irradiation, and annealing. It is concluded that the results are not consistent with the well-known space-charge polarization theory of Joffé, according to which the buildup of space charge occurs because of blocking of the current carriers at one or both electrodes. Rather, it is necessary to regard the time-dependent polarization as a dielectric relaxation phenomenon. According to this viewpoint, the final conductivity, and not the initial value, represents the true ionic conductivity. Possible relaxation mechanisms are discussed in terms of defect clusters and charged jogs on dislocations.

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