The OH-OD exchange of kaolin minerals through contact with D2O introduced into interlayer space via intersalation resulted in a partial shift of the OH absorption bands. The total decrease in OH absorbance upon deuteralion was 52, 56, and 47% for the kaolinite, dickite-nacrite, and halloysite respectively, but the percentage decrease differed for the different absorption maxima of any one mineral. A secondary OH—OD exchange in the deuterated specimens was also observed upon heating to 350 and 400° C. These data together with the lack of deuteration in montmorillonite, and available orientation data on the kaolin OH groups by infrared spectroscopy, suggest that only two-thirds of the inner-surface OH groups form the interlayer OH—O bonds.

The densities of two allophane samples measured by displacement with water were 2·72–2·78 g/cm3, while those measured by a float-sink test in CH3OH-, CH3 COCH3-, C6H6- and CCl4-C2H2Br4 mixtures were 1·84, 1·94–1·98, 2·35 and 2·35–2·39 g/cm3, respectively. The results of the density determinations for montmorillonite, kaolinite, halloysite, imogolite and volcanic glass are also reported. The data were interpreted in terms of the accessibility of the displacement liquids to void spaces within and between the layers or ‘structure units’ of the minerals and a model of the ‘structure units’ of allophane is proposed.

Both YBa2Cu4O8 and (Y0.95Ca0.05)Ba2Cu4O8 were successfully prepared by firing for 160 h at 850 °C and at oxygen partial pressure of 3 atm without using any catalysts. These samples were characterized in terms of the crystallographic structure and thermal and superconducting properties. The x-ray powder diffraction patterns and superconducting properties for these samples were little changed after post-annealing for 6 h at 1070 °C and at oxygen partial pressure of 400 atm. However, when heat-treated at 700 °C in air and then quenched into liquid nitrogen, samples without post-annealing showed broader superconducting transitions than those post-annealed. Actually, the sharpness of the superconducting transition for a post-annealed sample was little affected by quenching. These observations were in agreement with the results of both transmission electron microscopy and thermal analyses.

UCGAS (undercut GaAs on Si) structures in which a part of the GaAs layer is separated from the Si substrate are newly developed to reduce both the thermal stress and the defect density. The stress distribution in the fabricated structures is evaluated by photoluminescence. Quite a good agreement between the measured and the analyzed distributions is obtained, and the stress in UCGAS is less than 1/10of that in planar GaAs on Si. The EPD (etch pit density) in UCGAS after thermal cycle annealing is also less than 1/10of that in the planar layer. UCGAS-LED is fabricated for the first time and tested. The UCGAS-LED emits in 7 meV shorter wavelength and has longer lifetime compared to the mesa-type LED fabricated from the same wafer.