Electronic, mechanical, and thermal properties of [Ca24Al28O64]4+(4e-) electride ceramic

The compound [Ca24Al28O64]4+ (e-)4 named as C12A7:e- has amazing properties with low work function and high electron conductivity due to its cage structure. For the application of the material as a hollow cathode in small satellite propulsion systems, its preparation as a ceramic is purposeful. But the mechanical and thermal properties of the C12A7:e- ceramic have only been insufficiently measured so far. In this study, the measured Vickers hardness (HV0.5) is 6.7 ± 0.2 GPa. Additionally, the ceramic has a fracture toughness of 1.6 MPaSRm (calculated by Shetty model) and a 4-pt. bending strength of s = 75 ± 12 MPa (s0 = 90 MPa). The coefficient of thermal expansion CTE is 6.0 × 10-6 K-1 (RT-1000 °C) and the thermal conductivity is between 2.3 W m-1 K-1 (20 °C) and 1.7 W m-1 K-1 (1000 °C). For calculating the thermal conductivity, the heat capacity and the thermal diffusivity are measured.