Redox Reactions in Glasses

The multivalent ions include some of the rare earth ions, transition metal ions and non-metal ions. There are many factors that affect the redox reaction of multivalent ions in glass, these factors include glass composition, melting conditions, type and concentration of the element and irradiation of the glass either by high energy ionized radiation or by laser. Different techniques were proposed for determining the redox states and speciation of polyvalent ions in glass that include analytical chemical titration methods, potentiometric methods, optical and photoluminescence spectroscopy and other techniques that rely on the use of X-rays such as X-ray absorption near edge structure (XANES), X-ray photoelectron spectroscopy (XPS) and extended X-ray absorption fine structure (EXAFS). Many of these techniques not only encounter some limitations that would be related to the applicability, accuracy or detection limit, but also some of them would impact the obtained result as it may over/underestimate the redox speciation; for example, the interaction between intense focused X-ray beam or electron beam and the sample during measurement could change the multivalent ion speciation. Some of the multivalent ions could be used as an indicator for the glass structural changes and could be also used to examine the formation of defect centers in glass upon irradiation. Glasses doped with multivalent elements are of practical importance as radiation shielding materials, optoelectronics materials, and optical data storage in high density memory devices, biomedical materials and white light-emitting diodes and in nuclear waste industry.