Conduction transition and electronic conductivity enhancement of cesium azide by pressure-directed grain boundary engineering

Abstract

Alkali metal azides have attracted considerable experimental and theoretical efforts as they are the promising starting materials for the synthesis of polymeric nitrogen, a high-energy-density material. This work reports the conduction behavior of cesium azide (CsN₃) under high-pressure using in situ impedance spectroscopy measurements. It is observed that pressure induces a transition from mixed ionic–electronic conduction to purely electronic conduction. The ionic to electronic transition was caused due to a sudden increase in the ionic migration barrier energy. Furthermore, grain boundaries were found to play a key role in the conduction process and served as high conductivity pathways for carrier transport at high pressures. The grain boundary effect improves the conductivity of CsN₃ by more than two orders of magnitude after one pressure cycle. This work provides critical insight into the structure–conduction relationship of CsN₃ and the role of grain boundaries in improving the conductivity of metal azides under high pressure.