[en] With Low-Temperature-Electron-Microscopy (LTSEM) it is possible to analyse the transport properties of solids at low temperatures. In particular it is possible to image the supercurrent density j_s in Josephson junctions. This was demonstrated by comparing TTREM-images with calculated values for j_s. In this thesis ramp-type Nd_2-xCe_xCuO_4-y/Nb-Josephson-junctions (NCCO/Nb) and Josephson junctions with a ferromagnetic interlayer Nb/Al-Al₂O₃/NiCu/Nb, so-called SIFS (superconductor-insulator-ferromagnet-superconductor) Josephson junctions were studied.It was demonstrated that LTSEM provides direct imaging of the sign change of the order parameter in superconductors with d_x²-y²-symmetry. This was a controversial issue over the last decade. A step like variation in the thickness of the F-layer allows the fabrication of linear and annular Josephson junctions with different numbers of 0 and π facets. With the LTSEM 0-, π-, 0-π-, 0-π-0-, 0/2-π-0/2-, 20 x (0-π)- as well as square-shaped-, circular- and annular-Josephson-junctions were studied. It was demonstrated, that these junctions are of good quality and have critical current densities up to 42 A/cm² at T=4.2 K, which is a record value for SIFS junctions with a NiCu F-layer so far. By comparing the measurements with simulations a first indication of a semifluxon at the 0-π-boundary was found. (orig.)