Electrical conductivity of Li2Ge7O15 crystals doped with Al.

Electrical conductivity σ was studied in single- and polycrystalline lithium heptagermanate Li2Ge7O15 doped with Al. In Li2Ge7O15:Al single crystal conductivity demonstrated strong anisotropy. As compared with pure crystal, doping significantly increased conductivity along the structural channels parallel to a and c axes. The doping effect was interpreted by supposing that Al3+ substituted for Ge4+ hosts. Li interstitials (ALi) were considered as the defects compensating charge imbalance introduced by the impurity. Heterovalent substitution Al3+(Ge4+) noticeably increased concentration of ALi which were mobile enough and contributed to conductivity. Influence of Al doping on σ was compared for Li2Ge7O15 single crystal and polycrystal. [ABSTRACT FROM AUTHOR]