Microanalysis of Glass Containing Alkali Ions

Abstract

The common problems connected with alkali ion migration during EPMA were studied on glasses containing nearly all possible alkali ions (Na, K, Rb, Cs). Binary silica glasses were prepared by melting from a very pure batch in Pt crucible. The glasses were carefully polished using alcohol to prevent surface corrosion by water and they were stored in vacuum. The specimens were coated with carbon layers approximately 30-nm thick and exposed to a 50-keV electron beam of 100 mm diameter. It was found that all alkali ions migrate under the electron beam, but the rate of the migration depends on the current density. The decay curves (characteristic X-ray intensity versus time) are similar in shape in all cases. The decay curve shows two transport regimes, the ®rst being linear-like, the second being the exponentiallike. The ®rst transport regime busts into the rapid alkali migration after a time known as the incubation period. The period is in general longer for the largeralkali ions size. It was found that even large rubidium and caesium ions migrate inside the glass with the same mechanism as sodium and potassium ions. While for K, Rb, and Cs ions the incubation periods were observed under the suitable experimental conditions, binary glass containing Na exhibits no observable incubation period. Except for the binary Na 2 O SiO 2 glass, the suitable experimental conditions for reliable quantitative EPMA can be found.

Structural control on bulk melt properties: Single and double quantum 29Si NMR spectroscopy on alkali-silicate glasses

“…The hygroscopic nature of the more alkali rich samples prevented the necessary sample preparation (polishing and coating) for microprobe analysis and/or the unstable nature of the glasses under the electron beam (Gedeon et al, 2000) rendered an accurate microprobe analysis impossible. Therefore, the composition of the K-silicate glasses was analyzed with an Axios XRF spectrometer (PANanalytical).…”

Effect of electron irradiation on Na–K silicate glass investigated using X-ray photoelectron spectroscopy and pattern recognition method

“…Migration of alkali metal ions, i.e. K, Na, Ca, Rb and Cs, was shown experimentally [5,9,[11][12][13][14][15] and explained in frame of different theoretical models [13][14][15]. Alkali atoms migration was observed using EPMA analysis [5].…”

“…These studies involved surface sensitive X-ray photoelectron spectroscopy (XPS) [1][2][3], Auger electron spectroscopy (AES) [4], electron microprobe (EPMA) [5], nuclear magnetic resonance (NMR) [6], infra-red spectroscopy [6], X-ray diffraction (XRD) [6,7], extended X-ray absorption fine structure spectroscopy (EXAFS) [8], Raman spectroscopy [9], molecular dynamics (MD) [10] and ion scattering spectroscopy (ISS) [11,12]. Migration of alkali metal ions, i.e.…”

Potassium surface enrichment in mixed alkali glass irradiated with electrons

“…The phenomenon can be observed even for the very low-energy beams. The changes induced in glass have been related with alternations in alkali spectrum-line found in electron probe microanalysis (EPMA) [3][4][5] or in Auger electron spectroscopy (AES) [6][7][8][9].…”