  Here we study the effect of Ca doping on charge transfer mechanism of
polycrystalline YBa2Cu3O7-{\delta} compound. The samples of composition
Y1-xCaxBa2Cu3O7-{\delta} (x = 0.00, 0.05, 0.10, 0.20 and 0.30) are synthesized
through standard solid state reaction route. Carrier doping is controlled by
annealing of samples in oxygen and subsequently in reducing atmosphere. Samples
are investigated using resistivity, dc magnetization (M-T) and magnetization
with field (M-H) measurements. With increase of Ca the transition temperature
(Tc) decreases in oxygenated samples, whereas the same increases in reduced
samples. Further reduction of samples at higher temperatures (> 600 0C) though
results in non-superconducting nature up to Ca concentration of x = 0.20, the x
= 0.30 sample is superconducting below 30K. This provides a remarkably simple
and effective way to study the relationship between structure,
superconductivity, and associated electronic properties. Variations in Cu1-O4,
Cu2-O4 and Cu2-O2 bond lengths with oxygen content, is seen through the
structural refinement of XRD pattern. The effective coordination of Cu2 atom
with oxygen changes with the change in theses bond lengths and hence the holes
in the CuO2 planes. The charge transfer mechanism from CuOx chains to CuO2
planes and thus effective hole doping is discussed in context of observed
results.
