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AEM quantification of phase compositions in SIALON-YAG ceramics

Conference ·
OSTI ID:6305441
Silicon nitride ceramics based on SIALON-YAG compositions have been shown to crystallize garnet (nominally Y3Al5O12) from a glassy matrix phase upon heat treatment of specimens hot-pressed with Y2O3 as a sintering aid (Lewis et al., 1980; Hohnke et al., 1981). It is of interest to accurately determine phase compositions in such materials in order to fully understand crystallization behavior and the development of microstructure. Upon initial inspection, these ceramics pose particular difficulties for quantitative AEM microanalysis. These difficulties are due in part to the extremely fine grain and intergrain dimensions, and to the potential for spectral artefacts to be generated by secondary fluorescence effects. The latter problem has been demonstrated in Ni-Ti analyses, for example (Angelini and Bentley, 1984), and was expected to be critical in the characterization of the garnet phase since both BSE's and yttrium x-rays can excite Si which is present in large concentration in bulk regions of ion-milled samples. The present report describes details of the quantification scheme developed for analysis of these specimens, and the experimental tests used to accurately characterize secondary fluorescence effects. The analysis techniques are applied to quantification of phases in hot-pressed and annealed specimens containing nominally 5 eq.% Al in the US -SIALON phase and 20 w/o garnet in annealed specimens.
Research Organization:
Michigan Univ., Ann Arbor (USA)
DOE Contract Number:
FG02-84ER45069
OSTI ID:
6305441
Report Number(s):
CONF-8509168-4; ON: DE86003866
Country of Publication:
United States
Language:
English