Correlation between the microstructure and the physical properties of HTSC single crystals and films. Final report

1. In order to carry out isothermic crystal growth experiments of YBCO the 123 primary crystallization field was determined by means of phase diagram investigations and crystal growth experiments at different oxygen partial pressure. 2. YBCO single crystals of high crystallographic perfection were grown and conclusions on the flux pinning mechanism were drawn. 3. By means of Liquid Phase Epitaxy (LPE) single crystalline (Tc∼90 K; ΔT≤0.5 K) c- and a,b- YBCO fils have been prepared on NdGaO3 and LaGaO3 substrates. The films were characterized structurally and magnetically. 4. Our fist melt textured YBCO ''single crystals'' possess intracrystalline critical current densities >104 A/cm2 at B≤2T. The irreversibility inductions are ≤6 T at 77 K. A simple demonstrator was constructed together with the IFW Dresden and a growth model was developed. 5. Using above all torque magnetometer measurements we separated intrinsic pinning effects from effects which are reasoned by the microstructure. 6. Own contributions to the theory of magnetic measuring methods resulted in the separation of geometric influences and influences of experimental arrangement, what leads to a clear interpretation of magnetic measurements carried out mainly with torque magnetometry and ac-susceptometry. (orig./MM)