X-RAY-EMISSION SPECTROSCOPY WITH EPMA APPLIED TO HIGH T(C) SUPERCONDUCTORS USING NEW SPECTROMETER CRYSTALS

The High Temperature Superconductors are characterized by a very aniso tropical structure and by typical arrangements of Cu- and O-atoms with in CuO2-planes. In studying the electronic structure of these compound s there is a strong demand for high resolution valence band spectrosco py. Using an electron probe microanalyzer we study the X-ray emission of O-K(alpha) and Cu-L(alpha) emerging from polycrystalline YBa2Cu3O7 and Tl2Ba2Ca2Cu3O10. The O-K(alpha) emission band is analyzed using a chlinochlore crystal in (001) orientation (2d = 28.4 angstrom). For th e Cu-L(alpha) emission band we use a beryl crystal in (1010BAR)-orient ation (2d = 15.9 angstrom). Furthermore, orientation dependent X-ray e mission spectroscopy of single-crystalline YBa2Cu3O7 and Tl2Ba2Ca1Cu2O 8 specimens was performed. We present the partial O-K(alpha) spectra w hich represent the O-2p(eta) (eta = x, y, z) electronic densities of s tates of the valence band and compare them with calculated data.