Hopping versus bulk conductivity in transparent oxides: 12CaO · 7Al ₂O ₃

A comparison of the electronic and optical properties of the mayenite-based oxide with the recently discovered transparent conducting oxides was described. The conductivity mechanism in the mayenite-based oxides is found to be different despite the apparent similarity of the characteristic optical absorption peaks. The connected charge-density maxima along the hopping path demonstrates the hopping nature of the conductivity. The high degree of delocalization of the conduction electrons obtained indicated that it cannot be classified as an electride.