Phase transitions in ytterbium under pressure (semimetal-semiconductor transition)

The semimetal-semiconductor transition in ytterbium has been studied in the pressure range 0.50 kbar and up to 600 degrees C using the Seebeck coefficient as a tool. In the FCC phase the thermoelectric power exhibits a marked increase with pressure and the semimetal-semiconductor transition is observed as a change in the slope. In the semiconducting phase the thermopower initially increases very rapidly with pressure followed by a steep decrease at higher pressures. The temperature coefficient of thermopower in the semiconducting phase increase is large and positive in contrast to the semimetallic phase. The FCC-HCP transformation at high temperatures is reported. A semimetal-semiconductor transition in the HCP phase has also been observed. The experimental results are discussed qualitatively on the basis of a simplified two-band model.