One-Step Preparation and Electrical Transport Characteristics of Single-Crystal Ca24Al28O66 Electrides

A single-crystal Ca24Al28O66 electride (C12A7:e−) with a length of 20 mm and a diameter of 10 mm was prepared in one step by the optical zone melting Al reduction method. The added Al powder not only serves as a composition component, but also serves as an in situ reducing agent for the preparation of single-crystal C12A7:e− The results of phase and structure analyses show that the prepared single-crystal C12A7:e− has good single crystal quality. The electrical properties and electronic state analysis results show that single-crystal C12A7:e exhibits a sharp Raman absorption peak of electron injection at 100–400 cm−−1, and an ultraviolet absorption peak at 2.8 eV. This indicates that the preparation method achieves effective electron injection while forming a single-crystal C12A7 structure. It is calculated that the electron concentration of single-crystal C12A7:e− with an Al powder content of 0.5 reaches 1.2 × 1018 cm−3. The results of first-principles calculations show that the single-crystal C12A7:e− has a cage-cavity conduction band (CCB) between − 1 eV and 0.7 eV, which is beneficial to electrical performance. The excellent electrical properties of single-crystal C12A7:e− are mainly derived from the contribution of d-state electrons of the Ca atoms.