The high-temperature superconductor, YBa2Cu3O7−x, deteriorates when exposed to aqueous and acidic vapors and solutions; these changes are clearly evident in ac susceptibility measurements. Decomposition products are determined by X-ray diffraction.

A technique to grow single crystals of the high-temperature superconductor YBa2Cu3O7- delta is described. The crystals are rectangular tablets up to 2*2*0.2 mm3 in size.

A new material with the nominal composition (Y0.4Ba0.6)CuO3 becomes superconducting at a temperature above 77 K.

The anelastic relaxation of lithium tantalate crystal is studied by using a multifunction inverted torsion pendulum. A relaxation internal friction (IF) peak is observed in the temperature range 100 degrees C to 350 degrees C and the orientation, domain and oxygen-deficiency effects on the IF peak are studied. The activation energy of this process is determined to be 1.26+or-0.02 eV and the IF peak is shown to be associated with the stress-induced anelastic motion of the electric domain boundaries.

Ceramic samples of the 90 K superconductor with nominal composition YBa2Cu307-, were made under varying preparation conditions. Some samples have a narrow transition-temperature range of about 1.5 K and a 100% "ac Meissner effect" near 77 K. The magnetic losses below 85 K were much reduced in these samples. Rietveld structure refinement in space group Pmmm using powder X-ray diffraction data showed significant oxygen vacancies in the square-planar CuOz chains parallel to the y axis in the y-z plane, and Cu disorder about the origin along the x axis. The sample with the superior superconducting properties has the formula YBa2C~306,92.