Floating Zone Growth and Characterization of (Ca(1–x)Nd(x))(12)Al(14)O(33+6x) (x ∼ 0.001) Single Crystals

[Image: see text] Rare earth Nd(3+) ion-doped Ca(12)Al(14)O(33) single crystals were grown at a rate of 1 mm/h by the floating zone technique in an oxygen atmosphere. The Nd concentration in the central area of the as-grown crystals was higher than that in the peripheral area due to the highly concave growth interface shape. The average Nd concentration in the as-prepared parallelepiped slices of ∼6 × 3 × 2 mm(3) for electride fabrication was ∼0.093 ± 0.011 atom % Nd in contrast to the nominal 0.1 atom % Nd concentration. The Nd-doped C12A7:Nd single crystalline electride prepared by thermal treatment with a Ti metal at 1100 °C for 48 h induced an insulator–metal transition with the highest conductivity of approximately 1165 S/cm. These annealing conditions provide an approach to completely remove clathrated oxide ions from the crystallographic cages, leading to the formation of C12A7:Nd(e(–)) and C12A7:e(–) electrides with high-density electrons (∼2.4 ± 0.2 × 10(21) and ∼1.8 ± 0.1 × 10(21) cm(–3)) localized in the cages. The carrier mobility at room temperature in C12A7:Nd(e(–)) was very similar to that in C12A7:e(–), even though it was very high at temperatures below ∼150 K.