The effect of zirconium segregation on hardening in the creep of fine-grained alumina was studied by using the tensile creep test. To avoid the effect of zirconia particle dispersion on creep, 100-ppm-zirconium-doped alumina and 1000-ppm-zirconium-doped alumina were fabricated by using a zirconium-containing precursor. The scanning transmission electron microscopy/energy-dispersive X-ray spectroscopy study revealed that the zirconium was segregated at the alumina grain boundary. Doping even as little as 100 ppm of zirconium caused the hardening effect. The creep rate was further reduced by increasing the amount of zirconium dopant. Although the stress exponent of 2 was not affected by zirconium segregation, the apparent activation energy of the creep was found to be increased, from 520 kJ/mol for undoped alumina to 670 kJ/mol for 100-ppm-zirconium-doped alumina and 760 kJ/mol for 1000-ppm-zirconium-doped alumina. It was suggested that grain-boundary sliding was accommodated by impuritydrag-controlled diffusional creep.

Ambipolar field-effect transistor (FET) device was fabricated with heterostructure of thin films of C 60 and pentacene. Three types of device structures in the C 60 /pentacene heterostructure FET device were studied in order to realize the best ambipolar properties. In the middle-contact type FET device of C 60 and pentacene, the mobility in p-channel operation was estimated to be 6.8 ϫ 10 −2 cm 2 V −1 s −1 , while the in n-channel operation was 1.3ϫ 10 −3 cm 2 V −1 s −1. This ambipolar FET device is available for a practical building-block to form CMOS integrated circuits with low-power consumption, good-noise margins, and ease of design.

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Nanocrystalline silicon carbide that was doped with boron and carbon (B,C-SiC) and contained 1 wt% boron additive and 3.5 wt% free carbon was fabricated using hot isostatic pressing under an ultrahigh pressure of 980 MPa and a temperature of 1600°C. The average grain size of the material was 200 nm. The tensile deformation behavior of this material at elevated temperature was investigated. The nanocrystalline B,C-SiC exhibited superplastic elongation of >140% at a temperature of 1800°C. High-resolution transmission electron microscopy observation and electron energy-loss spectroscopy analysis revealed that this nanocrystalline SiC did not have a secondary glassy phase at the grain boundary and the grain boundary had a strong covalent nature, which means that an intergranular glassy phase was not necessary to obtain superplasticity of covalent materials.

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