Practical Aspects of the Electron Probe Analysis of Boron in Silicates using a LSM Device with Large 2d

The development of Layered Synthetic Microstructures (LSM; also called Layered Dispersion Elements-LDE and, inaccurately, PseudoCrystals-PC) through the 1980's provided electron probe analysts using wavelength-dispersive spectrometry (WDS) access to the K-alpha emissions of the ultralight elements down at least to boron (Z=5) in the periodic table [1]. Although quite a bit has been reported subsequently about analytical methods for boron [2], little discussion has been directed at optimizing analysis on the basis of the type of diffraction element used or the effect of matrix type on the intensity and shape of the background (Bremsstrahlung) surrounding B K in silicate or borate materials. Regardless of the type of diffraction device, the B K peak is very broad and measuring its intensity from most silicate and borate matrices is complicated by sharply increasing background intensity on the high-energy side of the peak (HEB: High-Energy Background) (Figure Using an LSM with 2d in the range of ~147-200 , diffraction of B K occurs at 2<<45 o (~27.4-19.8 o ) and so removes most of the polarization-induced changes in peak shape as a function of orientation from crystalline materials with symmetries between those of the cubic and triclinic systems. The original LSMs with 2d in the 145-200 range are Mo-B 4 C interlayer devices. The first principal task of analysis with these devices is choosing a peak position and background offsets (or single offset and slope) that minimize or eliminate intensity from internal fluorescence of the B 4 C interlayers (Figure Pulse height analysis methods need to utilize the Differential Mode in order to eliminate high-order diffractions of higher-energy x-ray emissions that, although reputedly are eliminated by LSMs, occur both under the B K peak and in the HEB.