Bulk analysis is the determination of the elemental composition of a homogeneous solid sample. For Bulk analysis with the GD technique the outer layers of the material may be automatically removed by a the sputtering process prior to analysis. This avoids misleading results due to surface contamination such as oxidation or residuals of the sample preparation process. After this 'pre-burn' the material eroded in the continuous sputter process is analysed. The acquired intensities are integrated. This process may be repeated to improve statistics of the measurement and to check a possible in-homogeneous distribution of the elements in the solid sample.
GDS can handle bulk applications like sheet, powder, fastener, pressed, and mounted samples. Even small samples like wire (0.25 mm diameter) can be accurately tested. Thin sheets (down to 0.05 mm in thickness) may be successfully analysed using a back plate and cooling puck. Thinner sheets may be analysed after gluing and pressing them on a flat metal block. The glue avoids deformation of the sheet, pressing assures good thermal contact, thus avoiding excessive heating of the sample and the glue. Just about any sample form can be characterised by glow discharge technology, providing a good vacuum seal can be achieved.
The picture shows the typical external sample mount of a glow discharge spectrometer: here on a LECO GDS850A.
First published on the web: 3 August 2007
Author: Thomas Nelis.