The heat transfer problem associated with pulse thermal diffusivity measurements is analyzed for the cases of (i) triangular pulses whose widths are comparable with the transit time of temperature fronts across a sample (finite pulse width effects), (ii) heat losses from sample faces, and (iii) the simultaneous occurrence of heat losses and finite pulse-width effects. Methods for the analysis of experimental results which are affected by these conditions are discussed. Tabular and graphical data which facilitate the analysis are given.

Conduction in single crystal and ceramic BaTiO3 has been investigated using a concentration cell and activation analysis. Ionic conduction occurs near 100°C in single crystals containing Fe2O3 while electronic conduction predominates in ``pure'' crystals from 100° to 600°C. Ceramic samples conduct predominately ionically at 100°C and electronically at 500°C. It is found that the iron ion is mobile in single crystals and that the titanium ion is immobile.

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Conductivities of polycrystalline solid samples of cerium hydride and gadolinium hydride were measured over the composition ranges H/Ce=0–2.5 and H/Gd=0–2.13 at room temperature and at elevated temperatures (400°—750°C). Conduction is metallic and the results for the two systems are very similar. The conductivity in the variable composition dihydride phase of each system decreases with increasing hydrogen content and is explained assuming that the hydrogen is anionic, taking its extra electron from the system's conduction band. Measurements of absolute Seebeck coefficients (CeH2.37, —17 μV/°C; GdH2.12, —6 μV/°C) support this model. The measured conductivity curves extrapolate to zero at CeH2.7 and GdH2.3. For the dihydride phases the composition dependencies of the conductivities are used to calculate carrier mobilities. The values obtained are in the range 1 to 10 cm2/V-sec. The conductivities of compositions H/M=0 to 2 show that the dihydrides can exist with hydrogen-to-metal ratios much less than 2.0. Ionic conduction has been found not to be important to the conduction mechanism from the results of a concentration cell measurement.

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