The ionic conductivity of pure, yttrium-doped, and sodium-doped cadmium fluoride has been determined from room temperature up to a maximum temperature of 500°C. Results show the mobile defect to be fluorine vacancies with an activation energy of motion of 0.44 eV. A mechanism is developed for the conversion of yttrium-doped CdF2 to a semiconductor based on vacancy motion. An anomalous conductivity curve is observed in crystals containing sodium impurity. Possible explanations for this are discussed in terms of association effects.

No abstract

The valence-band photoemission of silver bromide and silver iodobromide has been measured with use of synchrotron radiation in the region of the Ag 4d Cooper minimum. The large change in ionization cross section in this region permits the determination of the individual halogen p and silver 4d partial densities of states (PDOS). The energy-distribution curves (EDC s) were recorded at liquid-nitrogen temperatures to prevent photolysis and take advantage of the significant line narrowing which occurs in the silver halides at low temperatures. The results are in good agreement with experiments using rare-gas resonance lines and with previously calculated energy-band structures. Changes in the halogen PDOS with the addition of iodide indicate that the narrowing of the band gap is due to the broadening of the uppermost antibonding halogen bands. The PDOS were calculated for pure AgBr using a nonrelativistic, self-consistent, Hartree-Fock theory and show good agreement with the experimental results.

No abstract