Electrochemical growth of nanometer-sized δ-Al2O3 single crystals by use of Al3+ conducting solid electrolyte

δ-Al2O3 single crystals, which are difficult to be grown in a single crystal form, were synthesized by dc electrolysis of the Al3+ ion conducting Al2(MoO4)3 solid electrolyte at extraordinarily low temperatures between 873 and 1023 K compared to the melting point of α-Al2O3 (ca. 2300 K). Electron diffraction patterns for each particle evidenced that the particles grown were metastable nano-sized δ-Al2O3 single crystals, and their particle sizes are appreciably smaller than 1.0 μm, which is the formation limit size of polycrystalline δ-Al2O3 obtained by the conventional methods.