Issues in the Wavelength-Dispersive Spectrometric Characterization of $\hbox {YBa}_{2}\hbox {Cu}_{3}\hbox {O}_{7 - \delta }$

YBa₂Cu₃O_7-δ (Y123) can have significant variation in oxygen content on a micron scale in superconducting devices, and this causes a range of superconducting properties-generally impairing the performance of the superconductor. This study initially aimed to determine variation in O content of Y123 using electron microprobe analysis. High-quality electron microprobe analysis requires flat, usually polished, samples. Polishing Y123 produces a change in O content in surface layers relative to that of the parent as polishing a ceramic involves partial to complete surface amorphization. The analyses are not appropriate for the parent (much lower O), evidence of inhomogeneity of oxygen is removed, and the resultant material absorbs oxygen from the environment. After ion milling, the new surface more reflects the parent; comparison of unprocessed materials with polished and milled ones suggests that milling does not seriously alter the O Kα peak shape. Furthermore, milled surfaces reveal inhomogeneities obscured in polished surfaces. O Kα peaks derived from milled surfaces were compared with those from standard oxides; all standards were found to have peak shapes that do not conform to those of Y123. Because peak width:height is markedly different, the analytical assumption that peak height is proportional to peak area is violated. Alternative methods of determining peak area without mapping the entire peak are required to perform high-quality Y123 analyses; these are being developed.