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

Local structures around a bismuth ion in bismuth‐doped silica glasses (BiSG) are analyzed using a Bi L III X‐ray absorption fine structure (XAFS). The XAFS spectrum of crystalline α‐Bi 2 O 3 was also measured for comparison with BiSG whose first peaks are about 0.1 Å less than α‐Bi 2 O 3 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 Bi 5+ –O bonding and the latter to Bi 3+ –O bonding compared with the Bi–O distances in typical crystals including Bi 3+ and Bi 5+ ions. The above results show that Bi ions in BiSG exist as both Bi 3+ and Bi 5+ states, which is also supported by X‐ray absorption near the edge structure spectra of BiSG.