Migration behavior of network-modifier cations at glass surface during electrical poling

X-ray photoelectron spectroscopy with C60-ion sputtering (C60-XPS) and electron spin resonance (ESR) revealed the migration behavior of network-modifier cations in an electrically poled soda-lime silicate glass. The Na+-deficient layer of 700-nm thickness was confirmed at the anode side surface. The Mg2 + and Ca2 + existed in the 200-nm thick layer from the top surface were concentrated in the layer of 200-700 nm depth from the surface. Additionally the oxygen content in the 200-nm thick layer decreased by the degassing as oxygen molecules from the glass surface, which is an essential requirement for the migration of Mg2 + and Ca2 + to cathode side. The bond scission between Si-O-Si is caused by the concentrated Mg2 + and Ca2 +, resulting the formation of SiO−(Mg2 + or Ca2 +)− OSi and Si· (Si E′ center). We have also confirmed the generation of oxygen hole center (NBOHC) and peroxy radical (POR) in the electrically poled soda-lime silicate glass.