The effect of substitution outside the CuO2 planes in YBa2Cu3O7-δ system

The samples with single 123 phase in series of Y1-xPrxBa2Cu3O-7-δ, YBa2-xMxCu3 · O7-δ (M = Sr, Ca) and YBa2Cu3-xCoxO7-δ were prepared and their Tc and nH were measured. Synthesizing the experimental results such as XAFS, neutron diffraction, XPS, and Raman shift etc., the following conclusions are reached: the substitution outside the CuO2 planes causes the apical 0(4) atom deviated from the optimum position in the crystal structure of YBa2Cu3O7, which results parts of the holes localized on Ba sites or CuO chains, thus decreases the mobile holes concentration of the system. The depression of Tc in such case mainly comes from the decrease of PH (holes per planer Cu). The delocalization effect of applied pressure is discussed