This work provides new insight and evidence that challenges and extends the accepted view of the oxidation behaviour of Kovar (ASTM-15). Specimens of 2 mm diameter Kovar wire were oxidised in air at 700 or 800°C for 10 min. The resulting oxide layers were analysed by X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy with energy-dispersive X-ray spectroscopy, scanning transmission electron microscopy and Raman spectroscopy. Oxide layers of approximately 2 and 4 lm thickness were formed at 700 and 800°C, respectively. These were found to contain iron, cobalt and traces of nickel. The combination of analysis techniques revealed that the oxide contains Fe 2 O 3 in addition to (Fe, Co, Ni) 3 O 4 , a spinel oxide, in contrast to the combinations of Fe 3 O 4 , Fe 2 O 3 and FeO that are typically reported. The oxide layer was found to be complex, consisting of multiple layers with different compositions, which is overlooked in the existing literature.Keywords Raman spectroscopy Á Spinels Á X-ray photoelectron spectroscopy (XPS) Á Scanning electron microscopy (SEM) Á Glass-to-metal seal

Kovar (Fe-29 Ni-17 Co wt%) is widely used in electrical components. For applications such as feed-throughs there is a requirement to join it to glass, forming a glass-to-metal seal. A controlled thickness, well adhered, oxide is desired on the Kovar to form a strong bond. The oxides formed on Kovar pre-oxidized, at 700 and 800 °C for ten min, have been analyzed. Each sample showed the presence of Fe2O3, CoO and NiO. XPS survey spectra and high resolution spectra were collected and are presented.

Kovar, a common glass-to-metal sealing alloy, has been analysed by XPS. Monochromatic aluminium and silver sources as well as an achromatic magnesiumx-ray source have been utilised to demonstrate the increased clarity of spectra that can be obtained through the use of each x-ray source in the analysis of a transition metal rich alloy.