Takao Kimura

Superconducting Oxides by the Sol-Gel Method Using Alkoxides

The superconducting oxide Y-Ba-Cu-O has successfully been fabricated by the sol-gel method using Y, Ba, and Cu alkoxides as starting materials. Powders with specific surface area of 15 m2/g are prepared by this method. An X-ray diffraction pattern attributed to a 1-2-3 structure appears at 750°C and a bulk sample with Tc of 90 K is made by 900°C sintering in an oxygen atmosphere. A film of Tc=80 K with c-axis orientation is also fabricated using the sol-gel paste on an yttrium-stabilized ZrO2 substrate.

Mechanical strength improvement of sol-gel derived dry gels for optical fiber preforms

Crack-free dry gels 85 mm in diameter for optical fiber preforms have been successfully fabricated by increasing their mechanical strength. Additions of fluorinated silicon ethoxide and SiO2 powder of low specific surface area into sol solution were effective in increasing the fracture strength of dry gels. The empirical relation of the apparent density and the strength of dry gels was found to be applicable in the range 0.45−0.65 g/cm2 d.

C -Axis-Oriented Superconducting Oxide Film by the Sol-Gel Method

In R-Ba-Cu-O systems (R=Y, Nd, Y-Nd), c-axis-oriented superconducting oxide films with Tc(zero)=90 K have been fabricated on yttrium-stabilized zirconia substrates. Oxide pastes for printing on the substrates are made by the sol-gel method using liquid alkoxides. Starting paste compositions that are Cu-rich and R-poor are found to be suitable for forming the c-axis-oriented superconducting oxide film.

High-Tc Superconducting Film on Silicon Substrate with ZrO2 Buffer Layer

A screen-printed YBa2Cu3O7-x superconducting film with Tc,zero=85 K has been fabricated on a ZrO2-coated silicon substrate made by the sol-gel technique. The ZrO2 buffer layer effectively protects the superconducting film from the interfacial reaction between the Y-Ba-Cu-O film and the Si substrate during the firing process.