Local Structures of Bismuth Ion in Bismuth‐Doped Silica Glasses Analyzed Using Bi LIII X‐Ray Absorption Fine Structure

Abstract

Local structures around a bismuth ion in bismuth‐doped silica glasses (BiSG) are analyzed using a Bi LIII X‐ray absorption fine structure (XAFS). The XAFS spectrum of crystalline α‐Bi2O3 was also measured for comparison with BiSG whose first peaks are about 0.1 Å less than α‐Bi2O3 in radial structure functions. According to curve‐fitting results using FEFF 8.2, the Bi–O distances of the first and second neighboring coordination spheres are estimated to be 2.1 and 2.3 Å, respectively. The former corresponds to Bi5+–O bonding and the latter to Bi3+–O bonding compared with the Bi–O distances in typical crystals including Bi3+ and Bi5+ ions. The above results show that Bi ions in BiSG exist as both Bi3+ and Bi5+ states, which is also supported by X‐ray absorption near the edge structure spectra of BiSG.