Polycrystalline C12A7 electrides were successfully synthesized via spark plasma sintering (SPS) process. C-2(2-) ions, generated from graphite by the spark plasma, presumably serve as a template for the formation of the C12A7 phase during the re-crystallization process and are spontaneously released from the cage of C12A7 during the SPS process, remaining mobile electrons in the cage. The polycrystalline C12A7 electride processed at 1100 degrees C exhibits an electrical resistivity of 1.7 x 10(-1) Omega center dot cm(-1), an electron concentration of 5.3 x 10(19)/cm(3) and optical absorptions of 0.4 eV and 2.7 eV at room temperature. (C) 2011 The Electrochemical Society. [DOI: 10.1149/2.021112esl] All rights reserved.