From n=1 to n=2 of the Ruddlesden Popper Phases via Ca-doping and induced effects on electrical and optical properties of La2-xCaxCuO4-δ

The results of the synthesis and characterization of the optimally doped La2xCaxCuO4-delta solid solution within the composition range 0.0 <= x <= 0.2 and x =1 are reported. In this study, we have been investigated the effects of Ca contents on the crystal structure, chemical stability, electrical conductivity, magnetic and optical properties of La2xCaxCuO4-delta materials. Preliminary X-ray powder diffraction (XRD) showed the presence of three structural phases in the series belonging to Ruddlesden-Popper Phases. The increase of the symmetry (from orthorhombic towards the tetragonal) for the substitution rate x (Ca) = 15% was evaluated by combined neutron and X-ray powder diffraction. Electrical conductivity measurements show that the appropriate Ca doping in La2CuO4 leads to noticeable increase in low-temperature dc conductivity and oxygen kinetics. The maximum dc conductivity sigma = 0.2386 S m(-1) at a selected temperature of 280 degrees C was obtained when x = 0.165. The analysis by the RPE technique shows that all the phases obtained are paramagnetic except the phase with a substitution rate x (Ca) = 15% is diamagnetic.