Electron Requirements of Bonds in Metal Borides

Abstract

Electrical measurements have been made on CaB₆, SrB₆, BaB₆, YB₂, YB₄, YB₆, and YB₁₂ for the purpose of testing models of the electronic structure of the boron atoms in the four boride types represented. The compounds CaB₆, 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.