LOCAL ELECTRONIC STRUCTURE OF DOPING ATOMS IN <font>MA</font>2<font>Ca</font>n-1<font>Cu</font>n<font>O</font>2n+3 HIGH-Tc SUPERCONDUCTORS WITH [<font>M</font>-12(n-1)n] TYPE STRUCTURES

Results of X-ray fluorescence measurements of MA 2 Ca n-1 Cu n O 2n + 3 compounds with [ M -12(n-1)n] type structures, ( C 0.8 N 0.2 Sr 2 CuO 5.3, [ Cu 0.25 (C,N) 0.75] Sr 2 CaCu 2 O y, Cu 0.5 V 0.5 Sr 2 CaCu 2 O 7.5, Cu 0.5 V 0.5 Sr 2 Ca 2 Cu 3 O 9.4, Cu 0.5 V 0.5 Sr 2( Ca 3.6 Sr 0.4) Cu 5 O 13.5 and Cu 0.5 V 0.5 Sr 2( Ca 4.7 Sr 0.3) Cu 6 O 15.3, are presented. The experiments show that C-atoms form a distorted CO 3 oxyacid group with a partial substitution of copper and nitrogen atoms in the M-sites. We conclude that the CO 32- group in (C,N) Sr 2 Ca n-1 Cu n O y and (Cu,C,N) Sr 2 Ca n-1 Cu n O y is substituted by the NO 2- which induces the creation of the hole carriers in these compounds. We have found that V-atoms in the given compounds form ( VO 4)3- tetrahedrons and have a pentavalent state.