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

Abstract

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.

Keywords

• 12CaO·7Al2O3
• [Ca24Al28O64]4+(4e−)
• C12A7
• CTE
• electride
• glass‐ceramic