Oxygen Tracer Diffusion in La _2‐x Sr _x CuO _4‐y Single Crystals

Abstract

The tracer diffusion of 18 O in La 2‐x Sr x CuO 4‐y single crystals (x = 0 to 0.12) has been measured from 400° to 700°C in 1 atm of oxygen using SIMS analysis. Evidence for diffusion by a vacancy mechanism was found at low strontium contents. Oxygen diffusivities for x 2≥ 0.07 were depressed by several orders of magnitude below the diffusivity for undoped La 2 CuO 4±y . The observed effects of strontium doping on oxygen diffusivity are discussed in terms of defect chemical models. The decreasing oxygen diffusivity with increasing strontium was attributed to the ordering of oxygen vacancies at large defect concentrations. A diffusion anisotropy, D ab / D c , of ∼600) was also found at 500°C.