Measurements of thermopower, resistivity, and thermal conductivity for the rare-earth intermetallic compounds CePd3 and CeIn3 indicate an anomalously large Peltier effect cooling figure of merit at low temperatures associated with a large thermopower. Resistivity and susceptibility measurements indicate that these compounds possess localized Ce 4f electrons which give rise to the Kondo effect and thermopower enhancement. These results suggest that a survey of Ce intermetallic compounds could lead to new materials for low-temperature thermoelectric cooling applications.
We determine bandwidths and critical-point positions with respect to the valence-band edge for the valence bands of several extensively studied semiconductors (with an accuracy of about 0.3 eV) by using photoemission densities of states derived from photoemission specti'a obtained in the 24-78-eV photon energy range. These photoemission spectra were obtained using synchrotron radiation from an electron storage ring; a double-pass, cylindrical, electrostatic, electron energy analyzer; and samples cleaved and measured in situ in ultrahigh vacuum. We give a detailed description of the data-reduction techniques by which electronic state densities and certain valence-band feature positions are determined from photoemission spectra. This description includes a discussion of the effect of various phenomena such as optical-transition-probability variations and Auger-emission peaks. Tables are presented which compare our valence-band-position values with the results of both empirical calculations fit to optical data as well as ab initio calculations. We find systematic and significant differences between experiment and calculations fit only to optical data, these differences increasing with crystal ionicity, while ab initio calculations generally give a better fit to experiment.
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