Oxidation behavior of ytterbium silicide in air and steam

Ytterbium (Yb)- and silicon (Si)-rich ytterbium silicides (Yb5Si3, and Yb3Si5) were successfully fabricated by arc-melting and heat treatment. The degradation behavior of both silicides was evaluated by means of oxidation tests under three different conditions: Air, air-H2O, and steam. The results showed that the degradation of these Yb-silicides in air was accelerated relative to that in air–H2O and in steam. Although Yb3Si5 formed an un-oxidized region in air–H2O and in steam, a complex phase transformation occurred as a result of the decrease in the amount of Yb in Yb3Si5, caused by exposure to heat, while the liquid phase evolved below the melting point of Si. The liquid phases did not form upon exposure of Yb5Si3 to heat, whereas Yb5Si3 was more oxidized and the amount of SiO2 formed during heat exposure in air-H2O and steam is higher than Yb3Si5. •Oxidation behaviors of Yb5Si3 and Yb3Si5 in air and steam were evaluated.•Yb5Si3 and Yb3Si5 were more oxidized in air than in steam.•Yb5Si3 was also more oxidized than Yb3Si5 because Yb was oxidized preferentially.•The formation of Yb-silicates prevented the growth of SiO2.