[Ca24Al28O64]4+(4e−) electrides ceramic with high-electron concentration rapidly fabricated by spark plasma sintering of Ca, Al organic powder precursor in spark plasma sintering

Abstract The electrides of [Ca24Al28O64]4+(4e−) (C12A7:e−) was quickly fabricated by Ca, Al organic powder precursor through spark plasma sintering (SPS) at 750 °C for 10 min. There exist a large amount of reducing gas CO generated by heating Ca, Al organic powder acting as a perfect reducing agent in the high-energy DC pulse current and DC electric field of the SPS. By analyzing the phase, elements, structural composition, and electronic state of the sample, it is found that the phase and elemental composition of the sample meet the standard C12A7:e− and the density of the sample is more than 99%. The EPR results show that the sample has a sharp absorption peak at a magnetic field strength of about 352 mT, and the ratio of the maximum value to the minimum amount of the absorption peak is 2.67. This EPR curve with Dyson characteristics indicates that there is a high density of unpaired electrons inside the sample. The sample showed a significant ultraviolet absorption peak at 2.5 eV, and the calculated electron concentration of the sample reached 2.3 × 1021cm−3. TG/DTA, Raman spectroscopy, and XPS result further fully proved the successful fabrication of C12A7:e−. The electronic structure of C12A7:e− calculated using the first-principles show that the CCB of C12A7:e− not only traverses the Fermi surface as a whole, but also shows a narrower state with a smaller effective mass of electron transition, and the energy between CCB and FCB is 0.68eV. This indicates that C12A7:e− has excellent electrical transport characteristics like typical metals, which mainly from the contribution of s-state electrons of Ca atoms and p-state electrons of Al atoms. The theoretical results support our experiments. This fabricating method makes rapid large-scale production of C12A7:e− with high electron concentration possible.