Microstructure of quasi-one-dimensional superconductor KCr 3 As 3 prepared by K-ion deintercalation

The microstructure of quasi-one-dimensional KCr As (133) superconductors, which were prepared by chemical cation deintercalation from their counterpart K Cr As (233) compounds, are investigated using scanning transmission electron microscopy. The nominal KCr As crystals generally exhibit irregular nanoscale 133-phase domains accompanied by an amorphous As-deficient phase and cracks as a result of alkali cation deintercalation processes. Analysis of local defective structures reveals the existence of an intermediate state in the transformation from 233 to 133 phase and a possible K-deficient 233-type structure as a nanoscale cluster. Our microscopic investigations offer insight into the microstructure of KCr As and the alkali metal cation deintercalation processes.