Oxygen diffusion in La2−x Srx CuO4−y

Abstract

Diffusion of 18O in the superconductor La2−x Srx CuO4−y has been measured as a function of x (0 to 0.20) between 300 and 500°C at an oxygen partial pressure of ≍ 1 atm. Concentration profiles were obtained using a secondary ion mass spectrometer. The diffusion coefficient decreases with increasing Sr additions from 0.1 to 0.2, primarily because of an increase in activation energy. This result, which is contradictory to the expectation that the diffusion coefficient should increase with increasing vacancy concentration caused by the added Sr, can be explained if oxygen vacancies are bound to Sr clusters. Measurements on samples with x = 0 or 0.05 were unsuccessful, probably because of porosity.