Electron requirements of bonds in metal borides

Abstract

Electrical measurements have been made on CaB6, SrB6, BaB6, YB2, YB4, YB6, and YB 12 for the purpose of testing models of the electronic structure of the boron atoms in the four boride types represented. The compounds CaB 6, SrB6, and BaB6 were found to be semiconductors. The Hall coefficients of YB2, YB6, and YB12 were measured and found to correspond to one free electron per yttrium atom in each compound. The Hall coefficient of YB4 was also measured, but could not be interpreted because the free-electron theory does not provide a theoretical value for comparison with experiment. The results are in agreement with the models which have been proposed.