Positron lifetime studies of defect structures in Ba1-xKxBiO3

This paper reports on temperature-dependent positron lifetime experiments performed from room temperature to cryogenic temperatures on Ba1-xKxBiO3 for x = 0.4 and 0.5. From the temperature dependence of the positron lifetime in the normal state, we observe a clear signature of competition between separate defect populations to trap the positron. Theoretical calculations of lifetimes of free or trapped positrons have been performed on Ba1-xKxBiO3, to help identify these defects. Lifetime measurements separated by long times have been performed and evidence of aging effects in the sample defect populations is seen in these materials