Oxygen-vacancy behavior in La2−xSrxCuO4−y by positron annihilation and oxygen diffusion

Abstract

Oxygen-diffusion and positron-annihilation results for ${\mathrm{La}}_{2-x}{\mathrm{Sr}}_x\mathrm{Cu}{\mathrm{O}}_{4-y}$ compounds are reported. A qualitative explanation of the observed results is given on the basis of a model in which the oxygen-vacancy concentration in ${\mathrm{La}}_{2-x}{\mathrm{Sr}}_x\mathrm{Cu}{\mathrm{O}}_{4-y}$ is determined by ${\mathrm{Sr}}^{2+}$ ion clustering on the La sublattice. This model also leads to a maximum in the ${\mathrm{Cu}}^{3+}$ ion concentration as a function of the ${\mathrm{Sr}}^{2+}$ ion concentration.