Growth and microstructure of superconducting YBa₂Cu₃O_x single crystals

We have developed a technique for growing free-standing, well-formed YBa2Cu3Ox single crystals from melts in the YBa2Cu3Ox-BaCuO2-CuO pseudoternary system. The crystals are rectangular prisms with the samllest dimension parallel to the c-axis of the unit cell. Fine-scale transformation twins are formed during cooling through the tetragonal-to-orthorhombic phase transition. Superconducting transitions of crystals annealed in oxygen (1 atm) at 420°C typically occur at 92 K with a width of 0.2 K. © 1987.