Mn2+ EPR investigation of sol-gel process in silica xerogels at 77 K

✍ Scribed by Sushil K Misra; Milan Mazúr; Peter Pelikán; Hana Hulínová; Marek Liška

• Book ID: 103939695
• Publisher: Elsevier Science
• Year: 1995
• Tongue: English
• Weight: 296 KB
• Volume: 210
• Category: Article
• ISSN: 0921-4526
• DOI: 10.1016/0921-4526(94)00917-k

✦ Synopsis

The EPR spectrum of the Mn 2+ ion has been used as a diagnostic tool at liquid-nitrogen temperature (77K) to investigate the structural evolution of SiO2 xerogels as a function of temperature during their calcination, as.well as during subsequent aging. The positions of the Mn 2 ÷ hyperfine lines were used to estimate the g-factor, the hyperfine interaction constant (A) and the zero-field splitting parameter (D) for the Mn 2 ÷ ion in the various xerogels. The values of the parameters g, A of the xerogels were found to be, within experimental error, independent of the firing temperature as well as that of aging. However, the splitting of the forbidden hyperfine lines, and thus the value of D, was found to be significantly different in the samples prepared at firing temperatures of 360°C and below from those prepared at firing temperatures of 440°C and above; they remained independent of aging.