The wetting behavior and reactivity between molten pure Gd and polycrystalline 3YSZ substrate (ZrO2 stabilized with 3
wt% of Y2O3) were experimentally determined by a sessile drop method using a classical contact heating coupled with drop
pushing procedure. The test was performed under an inert flowing gas atmosphere (Ar) at two temperatures of 1362 °C and
1412 °C. Immediately after melting (Tm=1341 °C), liquid Gd did not wet the substrate forming a contact angle of θ=141°.
The non-wetting to wetting transition (θ < 90°) took place after about 110 seconds of interaction and was accompanied by
a sudden decrease in the contact angle value to 67°. Further heating of the couple to 1412 °C did not affect wetting
(θ=67°±1°).
The solidified Gd/3YSZ couple was studied by means of optical microscopy and scanning electron microscopy coupled
with X-ray energy dispersive spectroscopy. Structural investigations revealed that the wettability in the Gd/3YSZ system is
of a reactive nature associated with the formation of a continuous layer of a wettable reaction product Gd2Zr2O7
.