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The term “special crystals” refers to crystal types and multilayers that are not used universally but are
employed in special applications.
LiF(420):
See, for example, “standard types” description of the LiF crystals (200, 220 and 420).
Ge:
A very good crystal for measuring the elements S, P and Cl. In comparison to PET, Ge is characterized
by a higher dispersion and a more stable temperature behavior. Ge suppresses the peaks of the 2nd and
4th order, in particular.
Ge is especially suitable for differentiating between sulphide and sulphate, such as in samples of cement.
Introduction to X-Ray Fluorescence (XRF) Fundamental Principles
ADP:
In practice, ADP is only used for the analysis of Mg and has a higher resolution with a significantly lower
reflectivity compared to the multilayer XS-55. ADP is therefore required where interference peaks can
occur such as in the case of low Mg concentrations in an Al matrix.
TlAP:
TlAP has high resolution but low reflectivity and is recommended for analyzing F and Na if the resolution
of XS-55 is insufficient (e.g. where Na is overlapped by the Zn-L peaks in Zn-rich samples).
DANGER
Disadvantages are the limited lifetime, toxicity, and high price.
InSb:
InSb is a very good crystal for analyzing Si in traces as well as in higher concentrations (e.g. glass). It
replaces PET and is used wherever high precision and great stability is required. The disadvantages are
the limited use (only Si) and the high price.
XS-N:
XS-N is a multilayer with a 2d-value of 11.0 nm, specially optimized for nitrogen.
XS-C:
XS-C is a multilayer with a 2d value of 12.0 nm, specially optimized for carbon.
XS-B:
XS-B is a multilayer with a 2d-value of 19.0 nm, specially optimized for boron and is equally suitable for
the analysis of beryllium.