Temperature dependences of dielectric constants, specific heat and D–E hysteresis loops of Li-doped zinc oxide ceramics were investigated. A new dielectric anomaly was found at 330 K in Zn1-x LixO with x=0.17. A cusp-like anomaly was also found in specific heat. A ferroelectric D–E hysteresis loop was successfully observed for the first time. These observations suggest that replacement of host Zn ions by small Li ions induces a ferroelectric phase in the wurtzite-type ZnO piezoelectric semiconductor. This material is a candidate for ferroelectric thin films in integrated ferroelectric devices.

Superoxide dismutase (SOD) is an enzyme that catalytically removes the superoxide radical (*O2-) and protects organisms from oxidative damage during normal aging. We demonstrate that not only the cytosolic *O2- level but also the mitochondrial *O2- level increases in the deletion mutants of sod-1 gene encoding Cu/Zn SOD in Caenorhabditis elegans (C. elegans). Interestingly, this suggests that the activity of SOD-1, which so far has been thought to act mainly in cytoplasm, helps to control the detoxification of *O2- also in the mitochondria. We also found functional compensation by other SODs, especially the sod-5 gene, which was induced several fold in the mutants. Therefore, the possibility exists that the compensative expression of sod-5 gene in the sod-1 deficit is associated with the insulin/insulin-like growth factor-1 (Ins/IGF-1) signaling pathway, which regulates longevity and stress resistance of C. elegans because the sod-5 gene may be a target of the pathway.

Ferroelectric properties and the effect of Li+ and Mg2+ dopants in II–VI semiconductor ZnO were studied. The ferroelectric D–E loops were observed in Zn1-x (Li0.02·Mg x-0.02)O, as well as in Zn1-x LixO. The transition temperature (T c) increases in proportion to the concentration of Mg2+ ions, while it is almost constant (330 K) in Zn1-x LixO above x > 0.1. T c was 260 K for Zn0.9(Li0.02Mg0.08)O and 360 K for Zn0.7(Li0.02Mg0.28)O. An additional 20% of Mg increases T c by 100 K. The ferroelectric phase transition is strongly influenced by the introduction of small Li and Mg atoms instead of the host Zn atoms in wurtzite ZnO.

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