THE SUBSTITUTION EFFECT OF CA2-PROPERTIES IN NONSTOICHIOMETRIC DY1-XCAXCOO3-Y SYSTEM( ION ON THE PHYSICAL)

The Dy1-xCaCoO3-y (0.00 less than or equal to x less than or equal to 1.00) compounds have been prepared by a drip pyrolysis technique. The electronic structure and the geometric environment of the solid soluti ons are determined with Co K-edge X-ray absorption near edge structure (XANES). In the absorption edge region, it has been observed that thr ee peak groups correspond to the 1s-->4p main transition allowed by th e electric dipole matrix, the shakedown transition of ligand to metal charge transfer process, and 1s-->3d quadrupole allowed transition, re spectively. In our comprehensive crystallographic investigation of the system, it is found that the DyCoO3 compound has a typical GdFeO3 str ucture with the space group of Pbnm. The compounds of x = 0.75 and 1.0 0 are formed with more than twice the size of an ideal perovskite unit cell and those of x = 0.25 and 0.50 include a microscopic binary phas e of CaCoO2.50. The electrical conductivities depend on the Ca2+ ion c ontent which affects the distortion of oxygen octahedra along the c-ax is and then the transition of pi to sigma* energy level. As a result of magnetic measurement, it is found out that low spin states of Co3ions are converted to high spin totally or partially around 550 K in t he compounds of x = 0.00-0.50. The constant ratios of low-high spin st ates at x = 0.75 and 1.00 are preserved in the given temperature regio n.