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

Abstract

The compound [Ca24Al28O64]4+(4e-) named as C12A7:e- has outstanding properties because of a low work function and high electron conductivity due to a cage-like crystal structure. For the application of the material as hollow cathodes in small satellite propulsion systems, its preparation as sinterable glass-ceramics via the powder route is purposeful. However, the mechanical and thermal properties of the C12A7:e- glass-ceramics have only been insufficiently measured so far. In this study, the measured Vickers hardness (HV0.5) is 6.7 ± 0.2 GPa. The ceramic has a fracture toughness of 1.6 MPa m0.5 (calculated by Shetty model) and a 4-pt. bending strength of σ = 75 ± 12 MPa (σ0 = 90 MPa). The coefficient of thermal expansion CTE is between 4.2 and 6.0 × 10−6 K−1 (RT-1000°C), and the thermal conductivity ranges 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.