Synthesis and physical properties of multilayered cuprates

The multilayered cuprates of HgBa2Can−1CunOy (Hg-system) and Ba2Can−1CunO2n(O, F) (F-system) (n = 5–9) have been synthesized under high-pressure to investigate the variation of Tc. The a- and c-parameters showed reasonable behavior: as the n increases from 5 to 9 the a-parameter approached that of an infinite layer CaCuO2 (IL) and the average interval of c (or c/2) was close to the c-parameter of the IL. All the samples showed high Tc values of about 100 and 80 K for Hg- and F-system, respectively. In addition, the Tc was almost constant for n ⩾ 5 for both systems. We have shown that the Tc variations can be explained using inhomogeneous charge distribution model as follows. The high Tc value is maintained because the charge reservoir layer supplies enough carriers for superconductivity to the adjacent CuO2 planes (OP) even for large n. The Tc is independent of n because the carrier concentration of OP is insensitive to n for large n.