Using in situ resistance measurements on diamond anvil cell, we have monitored the pressure and temperature dependence of the CaB6 electronic transport properties. We report that CaB6 is a semiconductor at room temperature and at ambient pressure, in contrast to previous studies suggesting a semimetal nature. From ambient pressure to 12 GPa, the CaB6 conductivity smoothly increases, and CaB6 behaves as a semiconductor, although the CaB6 conductivity shows a metallic temperature dependence over a temperature interval ranging from 110 to 300 K due to its extrinsic region (where an increase in the temperature produces no effect on the CaB6 sample carrier densities and the CaB 6 conductivity is, therefore, solely determined by the carrier mobilities). At around 12.4 GPa, CaB6 undergoes a metalliclike transition leading to a change in the CaB6 conductivity by a factor exceeding three orders of magnitude. This large increase in the CaB6 conductivity has been interpreted as resulting from an overlap between the conduction band and the valence band. From 12.4 to 26 GPa, the CaB6 conductivity markedly increases and is similar to a metallic one.
ASJC Scopus subject areas
- Physics and Astronomy(all)