IFEG   20353
INSTITUTO DE FISICA ENRIQUE GAVIOLA
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Towards a standardless quantification by electron probe microanalysis
Autor/es:
J. C. TRINCAVELLI
Lugar:
Guarujá, San Pablo, Brasil.
Reunión:
Congreso; VII Encontro da Sociedade Brasileira de Pesquisa em Materiais (SBPMat); 2008
Institución organizadora:
Sociedade Brasileira de Pesquisa em Materiais
Resumen:
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Quantitative characterisation by electron probe microanalysis (EPMA)
is conventionally based on the comparison of the X-ray spectrum emitted by the
unknown sample with spectra originated from well known samples (standards). The
need of measuring spectra from standards may pose two limitations: on the one
hand, a long time is required when a great number of spectra must be registered;
on the other hand, the analysable samples are restricted according to the set
of standards available.
In view of the mentioned inconveniences, several attempts devoted to
the implementation of standardless quantification algorithms have been carried
out during the last decades. Nevertheless, the developed methods are mostly
useful as semi-quantitative approximations.
This kind of methods faces multiple difficulties, because for the
successful application of standardless EPMA analysis, everything must be well
known. That is to say, in addition to measure the sample spectrum in adequate
experimental conditions, diverse instrumental parameters, such as the
efficiency of the spectrometer used and the distortion of the characteristic
lines produced by the detection system, must be properly known. Moreover,
realistic expressions for the description of the generation and absorption of
the characteristic spectrum and bremsstrahlung are necessary. These expressions
depend on a number of atomic parameters including ionisation cross-sections,
relative transition probabilities, fluorescence yields, diagram and non-diagram
line natural widths, etc.
Results obtained for several of the mentioned instrumental and
atomic parameters will be shown, as well as their implementation in a
standardless quantification algorithm. Finally, future perspectives will be
discussed; particularly, the possibility of quantifying elements present in
different oxidation states.