Synthesis, Reduction, and Electrical Properties of Macroporous Monolithic Mayenite Electrides with High Porosity

Room-temperature stable macroporous mayenite electride (C12A7:e - ) has been successfully prepared via a sol-gel method accompanied by phase separation, followed by heat-treatment and reduction processes. The obtained xerogel monoliths possess controllable macrostructure and a porosity of more than 60%, depending on adjusting the amount of poly(ethylene oxide) as a phase separation inducer. Heat-treatment allows the formation of multicrystals Ca 12 Al 14 O 32 Cl 2 and Ca 12 Al 14 O 33 (C12A7), and the porosity increases to 78.67% after being heat-treated at 1100 °C. Further reduction promotes the transformation from Ca 12 Al 14 O 32 Cl 2 or C12A7 to C12A7:e - as well as the conversion from an insulator to a semiconductive electride. The carrier concentration of the electride reaches 3.029 × 10 18 cm -3 after being reduced at 1100 °C under Ar atmosphere, and the porosity still remains 66%. The macrostructure of the resultant mayenite electride before and after heat-treatment and reduction is perfectly preserved, indicating that the obtained macroporous monolithic mayenite electride could be utilized in the electronic components.