High Tc superconductors - From material to applications

Whereas the low Tc superconducting materials have emerged in some niche applications, high Tc materials are dedicated to numerous large scale applications due to their higher operating temperature. But, time and developments are required to elaborate them under long length, low cost wires. The most important features are their important anisotropy and their large sensitivity to grain misalignment for high transport currents. Texturation and even epitaxy are the concept basis for their processing. Two compounds are more particularly studied for high Tc wires : BiSrCaCuO and YBaCuO. The first high Tc wire generation are the Bi-PIT (Powder in Tube) tapes. These tapes have reached a pre-commercial stage, in particular with the commissioning of a production unit of up to 20 000 kilometers per year. The coated conductors using Y are the second high Tc wire generation. They are based on a flexible metallic substrate with a biaxial textured surface on which a YBCO layer is deposited. Great hopes are in the coated conductors since they should meet the cost and performance requirements. The large scale high Tc applications are at the stage of prototype (propulsion motors, electric power cables,...). But anyway the superconductor, which should be low cost and high quality, remains the major issue to develop applications. Different applications will be presented with development programmes throughout the world.