Enhancement of n-type electronic conductivity in bismuth iron borate glasses by fluorine addition

It was reported that a bismuth iron borate amorphous oxide glass, 10Fe3O4–45Bi2O3–45B2O3, exhibits a low electronic conductivity (σ) of ∼10−8 S/cm at room temperature. In this study, we have found that fluorine addition drastically enhances its σ to six orders of magnitude higher σ of ∼10−2 S/cm in a 21Fe3O4–4BiF3–30Bi2O3–45B2O3 glass. Additionally, it is experimentally confirmed that a high electron density of ∼1017 cm−3 at 400 °C is achieved. X-ray photoemission spectroscopy reveals Bi–F, Fe–F, and B–F bondings, supporting the fluorine substitution at oxygen sites. The fluorine-added bismuth iron borate glass would be expected in semiconductor applications such as a thermistor operating at 25–400 °C.